TY - CHAP A1 - Schmidt, Heiko A1 - Jimenez, Carmen T1 - Numerical study of the response of OH* chemiluminescence in planar premixed flames to acoustic forcing T2 - Proceedings of SPEIC10: Towards Sustainable Combustion, Tenerife 16-18 June 2010 Y1 - 2010 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/2010_SPEIC_Tenerife.pdf ER - TY - GEN A1 - Mellado, Juan Pedro A1 - Stevens, Bjorn A1 - Schmidt, Heiko T1 - Wind shear and buoyancy reversal at the stratocumulus top T2 - Journal of the Atmospheric Sciences N2 - A numerical experiment is designed to study the interaction at the stratocumulus top between a mean vertical shear and the buoyancy reversal due to evaporative cooling, without radiative cooling. Direct numerical simulation is used to eliminate the uncertainty introduced by turbulence models. It is found that the enhancement by shear-induced mixing of the turbulence caused by buoyancy reversal can render buoyancy reversal comparable to other forcing mechanisms. However, it is also found that (i) the velocity jump across the capping inversion Du needs to be relatively large and values of about 1ms21 that are typically associated with the convective motions inside the boundary layer are generally too small and (ii) there is no indication of cloud-top entrainment instability. To obtain these results,parameterizations of the mean entrainment velocity and the relevant time scales are derived from the study of the cloud-top vertical structure. Two overlapping layers can be identified: a background shear layer with a thickness (1/3)(Du)2/Db, where Db is the buoyancy increment across the capping inversion and a turbulence layer dominated by free convection inside the cloud and by shear production inside the relatively thin overlap region. As turbulence intensifies, the turbulence layer encroaches into the background shear layer and defines thereby the entrainment velocity. Particularized to the first research flight of the Second Dynamics andChemistry of theMarine Stratocumulus (DYCOMS II) field campaign, the analysis predicts an entrainment velocity of about 3mms21 after 5–10 min—a velocity comparable to the measurements and thus indicative of the relevance of mean shear in that case. Y1 - 2013 UR - http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-13-0189.1 SN - 1520-0469 VL - 71 IS - 3 SP - 1040 EP - 1057 ER - TY - CHAP A1 - Movaghar, Amirreza A1 - Linne, Mark A1 - Oevermann, Michael A1 - Meiselbach, Falko T. A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - Numerical study of liquid breakup at the surface of turbulent liquid jets using One-Dimensional Turbulence T2 - 26th Annual Conference on Liquid Atomization and Spray Systems, ILASS, proceedings of the Conference, Bremen, Germany, 08.09.2014 - 10.09.2014 N2 - This paper presents an investigation of primary breakup of planar turbulent liquid jets and breakup properties at the surface of turbulent jets in still air at standard conditions. Numerical simulations are carried out for jet exit Reynolds number 23000 and Weber numbers in the range [102–107]. Due to the limitation of direct numerical simulation (DNS) to moderate Reynolds numbers, a stochastic 1D ansatz based on the one-dimensional turbulence (ODT) model is used to simulate a planar liquid jet with a high lateral resolution. ODT permits an affordable high resolution of interface and single-phase property gradients which are key for understanding the local behavior. ODT is a stochastic model simulating turbulent flow evolution along a notional 1D line of sight by applying instantaneous maps to represent the effect of individual turbulent eddies on property profiles. The most relevant mechanisms that influence the primary breakup of liquid jets are found to be represented accurately based on comparisons to experiments and correlations reported in the literature. Building on this finding, future work will focus on the statistics of droplets generated by primary breakup, both to investigate their relationship to breakup mechanisms and to provide input to models of secondary breakup and subsequent spray evolution. Y1 - 2014 SN - 978-3-00-047070-7 CY - Bremen ER - TY - CHAP A1 - Mellado, Juan Pedro A1 - Stevens, Bjorn A1 - Schmidt, Heiko T1 - Wind shear and evaporative cooling at the stratocumulus top T2 - 21st Symposium on Boundary Layers and Turbulence, 9-13 June 2014, Leeds, United Kingdom N2 - Turbulent entrainment at the stratocumulus top and its interaction with local processes like radiative or evaporative cooling still remains a source of uncertainty in current atmospheric models. The reason is, at least partly, that the characteristic scales at which those cloud-top processes occur are relatively small, of the order of a few tens of meters, and access to accurate data at those scales has been difficult. In this contribution, we present a simplified model designed to investigate these cloud-top processes in detail and we address some questions regarding the role of buoyancy reversal by evaporative cooling at the cloud top. As a tool, we use direct numerical simulation to remove the uncertainty associated with turbulence models. Buoyancy reversal refers to the formation of negatively buoyant parcels of fluid within an otherwise stable stratification as a consequence of the local cooling caused by the evaporation of the droplets at the cloud interface. This process leads to convective instability, as heavier parcels of fluid lie on top of lighter ones. This instability promotes turbulence, and hence entrainment and further evaporation of droplets, a feedback process that could eventually lead to a rapid dessication of the cloud -- the so-called cloud-top entrainment instability. Recent work has demonstrated that, in contrast to previous postulates, buoyancy reversal caused by evaporative cooling is not a sufficient condition to break up the cloud: turbulence is indeed enhanced, but very mildly. The reason is that buoyancy reversal alone leads to a meta-stable layer as the mixing rate, or entrainment rate, is diffusively limited, so that the eventual breakup of the cloud by buoyancy reversal alone occurs on time scales that are much too long to be relevant to the stratocumulus-top boundary layer. To become relevant, evaporative cooling requires the interaction with other local mechanisms of turbulence generation, like wind shear or radiative cooling. In this work, we study wind shear effects, without radiative cooling. There are at least two reasons to study shear effects. First, shear is ubiquitous, as local shear associated with large-scale eddies will also be evident even in the absence of a mean wind. Second, shear alone cannot sustain a continuous deepening of the layer, as shear generated turbulence will locally thicken the entrainment zone, but in the absence of other sources, the turbulence will eventually decay once a critical entrainment-zone thickness is reached. The latter makes it interesting to combine shear with the convective destabilization of the cloud-top layer through buoyancy reversal, as neither process acting alone is efficient in supporting significant mixing at the cloud top. In contrast, by generating convective eddies which locally thin the entrainment zone, buoyancy reversal might help enhance shear, which in turn locally enhances the mixing which sustains the buoyancy reversal, raising the possibility that the processes are self-reinforcing. Results show that the enhancement by local wind shear can render buoyancy reversal comparable to other forcing mechanisms. However, we also find that (i) the velocity jump across the capping inversion, Δu, needs to be relatively large and typical values of about 1 m s-1 associated with the convective motions inside the boundary layer are generally too small, and (ii) there is no indication of cloud-top entrainment instability. To obtain these results, parametrizations of the mean entrainment velocity and the relevant time scales are derived from the study of the cloud-top vertical structure. Two overlapping layers can be identified: a background shear layer with a thickness (1/3) (Δu)2/(Δb), where Δb is the buoyancy increment across the capping inversion, and a turbulence layer dominated by free convection inside the cloud and by shear production inside the relatively thin overlap region. As turbulence intensifies, the turbulence layer encroaches into the background shear layer and defines thereby the entrainment velocity. Particularized to the first research flight of the Second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) field campaign, the analysis predicts an entrainment velocity of about 3 mm s-1 after 5-10 minutes, a velocity comparable to the measurements and thus indicative of the relevance of mean shear in that case. Y1 - 2014 UR - https://ams.confex.com/ams/21BLT/webprogram/Paper247674.html ER - TY - CHAP A1 - Glawe, Christoph A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - ODTLES: Mulitscale turbulence modeling and buoyant application T2 - Book of abstracts, 7th European Postgraduate Fluid Dynamics Conference, Ilmenau, Germany, 14th - 17th, July 2014 Y1 - 2014 CY - Ilmenau ER - TY - GEN A1 - Jozefik, Zoltan A1 - Kerstein, Alan R. A1 - Schmidt, Heiko A1 - Lyra, Sgouria A1 - Kolla, Hemanth A1 - Chen, Jackie H. T1 - One-dimensional turbulence modeling of a turbulent counterflow flame with comparison to DNS T2 - Combustion and Flame Y1 - 2014 SN - 1556-2921 VL - 162 IS - 8 SP - 2999 EP - 3015 ER - TY - GEN A1 - Schmidt, Heiko A1 - Glawe, Christoph A1 - Jozefik, Zoltan A1 - Meiselbach, Falko T. A1 - Kerstein, Alan R. T1 - On the benefits of ODT-based stochastic turbulence modeling T2 - Proceedings in applied mathematics and mechanics : PAMM N2 - We summarize the group’s progress in applying, analyzing, and improving ODT and ODT-based stochastic turbulence models like ODTLES. Compared to DNS these models span a wider range of scales while compared to RANS/LES (i) the molecular effects are retained and (ii) no assumption of scale separation is made. In this regard ODTLES has more properties of DNS than of standard LES. Y1 - 2014 SN - 1617-7061 VL - 14 IS - 1 SP - 655 EP - 656 ER - TY - CHAP A1 - Jozefik, Zoltan A1 - Kerstein, Alan R. A1 - Schmidt, Heiko ED - King, Rudibert T1 - Towards a compressible reactive multiscale approach based on One-Dimensional Turbulence T2 - Active Flow and Combustion Control 2014 N2 - Due to its huge complexity, progress in understanding and prediction of turbulent combustion is extremely challenging. In principle, progress is possible without improved understanding through direct numerical solution (DNS) of the exact governing equations, but the wide range of spatial and temporal scales often renders it unaffordable, so coarse-grained 3D numerical simulations with subgrid parameterization of the unresolved scales are often used. This is especially problematic for multi-physics regimes such as reacting flows because much of the complexity is thus relegated to the unresolved small scales. One-Dimensional Turbulence (ODT) is an alternative stochastic model for turbulent flow simulation. It operates on a 1D spatial domain via time advancing individual flow realizations rather than ensemble-averaged quantities. The lack of spatial and temporal filtering on this 1D domain enables a physically sound multiscale treatment which is especially useful for combustion applications where, e.g., sharp interfaces or small chemical time scales have to be resolved. Lignell et al. recently introduced an efficient ODT implementation using an adaptive mesh. As all existing ODT versions it operates in the incompressible regime and thus cannot handle compressibility effects and their interactions with turbulence and chemistry which complicate the physical picture even further. In this paper we make a first step toward an extension of the ODT methodology towards an efficient compressible implementation. The necessary algorithmic changes are highlighted and preliminary results for a standard non-reactive shock tube problem as well as for a turbulent reactive case illustrate the potential of the extended approach. Y1 - 2014 SN - 978-3-319-11967-0 SN - 978-3-319-11966-3 SP - 197 EP - 211 PB - Springer CY - Switzerland ER - TY - GEN A1 - Dietze, Eckhard A1 - Schmidt, Heiko A1 - Stevens, Bjorn A1 - Mellado, Juan Pedro T1 - Controlling entrainment in the smoke cloud using level set-based front tracking T2 - Meteorologische Zeitschrift N2 - Although large-eddy simulation (LES) has been shown to produce a reasonable representation of the turbulent circulations within the stratocumulus-topped boundary layer, it has difficulties to accurately predict cloud-top entrainment rates. In this paper, we present a front-tracking algorithm for LES to untangle the numerical and physical contributions to entrainment. Instead of resolving the cloud-top inversion, we treat it as a discontinuity separating the boundary layer from the free atmosphere and use the level set method to track its location. We apply our method to the smoke cloud test case as presented by BRETHERTON et al. (1999) which is simpler than stratocumulus in that it is only driven by radiative cooling avoiding evaporative feedbacks on entrainment. We present three-dimensional LES results with and without use of the level set method varying the grid resolution and the flux limiter. With the level set method, we prescribe zero entrainment and use this case to evaluate our method’s ability to maintain a non-entraining smoke-cloud layer. We use an empirically-based entrainment law to estimate numerical errors. With the level set method, the prescribed entrainment rate was maintained with errors about one order of magnitude smaller than the entrainment errors found in the standard LES. At the same time, the dependence of the entrainment errors on the choice of the limiter was reduced by more than a factor of 10. Y1 - 2014 U6 - https://doi.org/10.1127/metz/2014/0595 VL - 23 IS - 6 SP - 661 EP - 674 ER - TY - CHAP A1 - Jozefik, Zoltan A1 - Frechen, Tobias Nanu A1 - Hinz, Christoph A1 - Schmidt, Heiko T1 - A cellular automata approach for modeling surface water runoff T2 - European Geosciences Union, General Assembly 2015, Vienna, Austria, 13 April - 17 May 2015 Y1 - 2015 UR - http://meetingorganizer.copernicus.org/EGU2015/EGU2015-12675.pdf N1 - EGU2015-12675 PB - European Geophysical Society CY - Katlenburg-Lindau ER - TY - CHAP A1 - Schmidt, Heiko T1 - On the benefits of using LEM- and ODT-based approaches in numerical combustion T2 - Fifteenth International Conference on 8 Numerical Combustion, Avignon (France), April 19-22, 2015 Y1 - 2015 UR - http://www.nc15.ecp.fr/files/content/sites/nc15/files/Proceedings_web.pdf SP - S. 23 ER - TY - CHAP A1 - Glawe, Christoph A1 - Schulz, Falko T. A1 - Gonzalez-Juez, Esteban D. A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - ODTLES Simulations of Turbulent Flows through Heated Channels and Ducts T2 - 8th International Symposium on turbulence and shear flow phenomena (TSFP8), 28–30 August 2013, Poitiers, France, vol. 2 N2 - A widely occurring problem in fluid dynamics either in engineering or e.g. hydrology is the turbulent transport through channels and ducts. ODTLES, a stochastic based multi-scale and multi-dimensional model, is a promising tool to describe these flows even including scalar proper- ties like temperature. We are quantifying the ability of ODTLES to describe the heated channel flow with respect to the Prandtl number and the flow through squared ducts with respect to the Reynolds number. Y1 - 2013 UR - http://www.tsfp-conference.org/proceedings/2013/v2/htc.pdf SP - 1 EP - 6 ER - TY - GEN A1 - Jozefik, Zoltan A1 - Kerstein, Alan R. A1 - Schmidt, Heiko A1 - Lyra, Sgouria A1 - Kolla, Hemanth A1 - Chen, Jackie H. T1 - One-dimensional turbulence modeling of a turbulent counterflow flame with comparison to DNS T2 - Combustion and Flame N2 - The one-dimensional turbulence (ODT) model is applied to a reactant-to-product counterflow configuration and results are compared with DNS data. The model employed herein solves conservation equations for momentum, energy, and species on a one dimensional (1D) domain corresponding to the line spanning the domain between nozzle orifice centers. The effects of turbulent mixing are modeled via a stochastic process, while the Kolmogorov and reactive length and time scales are explicitly resolved and a detailed chemical kinetic mechanism is used. Comparisons between model and DNS results for spatial mean and root-mean-square (RMS) velocity, temperature, and major and minor species profiles are shown. The ODT approach shows qualitatively and quantitatively reasonable agreement with the DNS data. Scatter plots and statistics conditioned on temperature are also compared for heat release rate and all species. ODT is able to capture the range of results depicted by DNS. However, conditional statistics show signs of underignition. Y1 - 2015 U6 - https://doi.org/10.1016/j.combustflame.2015.05.010 SN - 0010-2180 VL - 162 IS - 8 SP - 2999 EP - 3015 ER - TY - GEN A1 - Jozefik, Zoltan A1 - Kerstein, Alan R. A1 - Schmidt, Heiko T1 - Simulation of shock–turbulence interaction in non-reactive flow and in turbulent deflagration and detonation regimes using one-dimensional turbulence T2 - Combustion and Flame N2 - The one-dimensional turbulence (ODT) methodology is extended to include an efficient compressible implementation and a model for capturing shock-induced turbulence is presented. Lignell et al. recently introduced a Lagrangian ODT implementation using an adaptive mesh. As the code operates in the incompressible regime (apart from constant-pressure dilatation) it cannot handle compressibility effects and their interactions with turbulence and chemistry. The necessary algorithmic changes to include compressibility effects are highlighted and our model for capturing shock- turbulence interaction is presented. To validate our compressible solver, we compare results for the Sod shock tube problem against a finite volume Riemannsolver. To validate our model for shock–turbulence interaction, we present comparisons for a non-reactive and a reactive case. First, results of a shock traveling from light (air) to heavy (SF6) with recheck have been simulated to match mixing width growth data of experiments and turbulent kinetic energy results from LES.Then, for one-step chemistry calibrated to represent an acetylene/airmixture we simulate the interaction of a shock wave with an expanding flame front, and compare results with 2D simulation (2D-sim) data for flame brush formation and ensuing deflagration-to-detonation transitions (DDT). Results for the Sod shock tube comparison show that the shock speed and profile are captured accurately. Results for the non-reactive shock–recheck problem show that interface growth at all simulated Mach numbers is captured accurately and that the turbulent kinetic energy agrees in order of magnitude with LES data. The reactive shock tube results show that the flame brush thickness compares well to 2D-sim data and that the approximate location and timing of the DDT can be captured. The known sensitivity of DDT characteristics to details of individual flow realizations, seen also in ODT, implies that model agreement can be quantified only by comparing flow ensembles, which are presently unavailable other than in an ODT run-to-run sensitivity study that is reported herein. Y1 - 2016 U6 - https://doi.org/10.1016/j.combustflame.2015.10.035 SN - 0010-2180 VL - 164 SP - 53 EP - 67 ER - TY - GEN A1 - Glawe, Christoph A1 - Schmidt, Heiko A1 - Kerstein, Alan R. A1 - Klein, Rupert T1 - XLES Part I: Introduction to Extended Large Eddy Simulation T2 - arXiv.org N2 - Direct numerical simulation (DNS), mostly used in fundamental turbulence research, is limited to low turbulent intensities due the current and future computer resources. Standard turbulence models, like RaNS (Reynolds averaged Navier-Stokes) and LES (Large Eddy Simulation), are applied to flows in engineering, but they miss small scale effects, which are frequently of importance, see e.g. the whole area of reactive flows, flows with apparent Prandtl or Schmidt number effects, or even wall bounded flows. A recent alternative to these standard approaches is the one-dimensional turbulence (ODT) model, which is limited to 1D sub-domains. In two papers we will provide a generalized filter strategy, called XLES (extended LES), including a formal theory (part I) and one special approach in the XLES family of models, called ODTLES (in part II (see Glawe et al. (2015))). ODTLES uses an ODT sub-grid model to describe all turbulent scales not represented by XLES, which leaves the larger scales to be simulated in 3D. This allows a turbulence modeling approach with a 3D resolution mainly independent of the turbulent intensity. Thus ODTLES is able to compute highly turbulent flows in domains of moderate complexity affordably and including the full range of turbulent and diffusive scales. The convergence of XLES to DNS is shown and the unconventional XLES advection approach is investigated in basic numerical tests. In part II, highly turbulent channel and duct flow results are discussed and show the future potential of XLES and ODTLES. Y1 - 2015 UR - http://arxiv.org/abs/1506.04930 ER - TY - GEN A1 - Glawe, Christoph A1 - Schmidt, Heiko A1 - Kerstein, Alan R. A1 - Klein, Rupert T1 - XLES Part II: From Extended Large Eddy Simulation to ODTLES T2 - arXiv.org N2 - In turbulence research and flow applications, turbulence models like RaNS (Reynolds averaged Navier-Stokes) models and LES (Large Eddy Simulation) are used. Both models filter the governing flow equations. Thus a scale separation approach is introduced for modeling purposes with the large scales simulated using a numerical scheme while smaller scales are assumed to be less important and might be modeled more or less easily. Unfortunately small scales are frequently of big importance, e.g. in reactive flows, wall bounded flows, or flows with significant Prandtl or Schmidt number effects. Recent alternatives to these standard models are the class of models based on the one-dimensional turbulence (ODT) idea, like ODTLES. The ability of ODT to capture highly turbulent flows (recently up to Reτ=6×105) allows ODTLES to realize 3D resolutions basically independent of the turbulent intensity. In two papers we provide a formal theory and application of an innovative modeling strategy for highly turbulent flows in domains of moderate complexity: In part I (see Glawe et al. (2015)) a new general filtering approach, called XLES (extended LES), is introduced. Contrary to LES, XLES is based on 2D filtering of the governing equations, whereby additional small scale terms are interpreted numerically. In this work a new ansatz for the ODTLES model is introduced as one special approach in the XLES family of models by incorporating the ODT model into XLES. The ODT model introduces microstructures not captured by the XLES filtered equations. To illustrate the ODTLES model capabilities, turbulent channel and duct flows up to friction Reynolds number Reτ=10000 are studied. Y1 - 2015 UR - http://arxiv.org/abs/1506.04938 ER - TY - CHAP A1 - Glawe, Christoph A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - ODTLES: A Multi-scale Ansatz for highly turbulent flows T2 - 15 The European turbulence conference, 25-28 august, 2015, Delft, The Netherland N2 - We use ODTLES, a multi-dimensional extension of the One-Dimensional-Turbulence model (ODT). ODT describes turbulent advection on a 1D sub-domain using a stochastic process for turbulent advection. These 1D sub-domains are coupled to obtain a 3D approach. ODTLES is applied to channel flow. Preliminary results for the pdf of the wall shear stress are compared to DNS. Y1 - 2015 UR - http://www.etc15.nl/proceedings/proceedings/documents/431.pdf ER - TY - CHAP A1 - Jozefik, Zoltan A1 - Kerstein, Alan R. A1 - Schmidt, Heiko T1 - Incorporation of acceleration effects into the One-dimensional-turbulence model, with application to turbulent combustion and shock-turbulence interactions T2 - 15th European Turbulence Conference 2015 August 25-28th, 2015, Delft, The Netherlands N2 - One-dimensional turbulence (ODT) is a stochastic simulation in which 3D turbulence effects are captured on a notional 1D line of sight by introducing instantaneous spatial rearrangements (maps) that represent advection by notional turbulent eddies. These eddy events incorporate the possibility of kinetic-energy changes that are equal and opposite to changes of other forms of energy such as the gravitational potential energy change due to a rearrangement of a vertical density profile. This illustrates that motion aligned with an applied force, in this case gravitation g, can be associated with energy change. Using this principle, we 1) present a model of turbulence interaction with the dilatational acceleration caused by thermal expansion in flames and show results for a turbulent counterflow flame with comparison to DNS and 2) present a model for shock-induced turbulence and show results for mixing width growth in a shock tube with comparison to experiments. Y1 - 2015 UR - http://www.etc15.nl/proceedings/proceedings/documents/356.pdf ER - TY - CHAP A1 - Sharma, Sparsh A1 - Sarradj, Ennes A1 - Schmidt, Heiko T1 - Unsteady Lift due to the Interaction of Incidence Turbulence with an Airfoil T2 - Fortschritte der Akustik, 43. Deutsche Jahrestagung für Akus tik, 6.-9. März 2017 in Kiel Y1 - 2017 UR - https://www.dega-akustik.de/fileadmin/dega-akustik.de/publikationen/DAGA/DAGA_17_Inhalt.pdf SN - 978-3-939296-12-6 SP - 1489 EP - 1490 PB - Deutsche Gesellschaft für Akustik e.V. (DEGA) CY - Berlin ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko A1 - Mauß, Fabian A1 - Jozefik, Zoltan T1 - Constant volume n-Heptane autoignition using One-Dimensional Turbulence T2 - Combustion and Flame N2 - Abstract Constant volume premixed lean n-Heptane/air autoignition at high pressure is investigated using the One-Dimensional Turbulence (ODT) model. The configuration consists of a 1D fixed volume domain with a prescribed velocity spectrum and temperature fluctuations superimposed on an initial uniformly elevated scalar field. The sensitivity of the heat release rate and pressure evolution to the initial temperature distribution is studied by imposing different initial temperature fields while holding the mean, RMS and integral length scale of the field constant. Three detailed chemical mechanisms are employed for the prediction of autoignition and heat release rate. To mitigate the high computational cost associated with the calculation of the chemical source terms in the stiff complex mechanisms, an approach based on the Strang-Splitting method is presented. Finally, a … KW - One-Dimensional Turbulence KW - n-Heptane autoignition Y1 - 2018 U6 - https://doi.org/10.1016/j.combustflame.2017.12.015 SN - 0010-2180 VL - 190 SP - 388 EP - 401 ER - TY - GEN A1 - Fragner, Moritz M. A1 - Schmidt, Heiko T1 - Investigating Asymptotic Suction Boundary Layers using a One-Dimensional Stochastic Turbulence Model T2 - Journal of turbulence N2 - The turbulent asymptotic suction boundary layer is studied using a one-dimensional turbulence (ODT) model. ODT is a fully resolved, unsteady stochastic simulation technique. While flow properties reside on a one-dimensional domain, turbulent advection is represented using mapping events whose occurrences are governed by a random process. Due to its reduced spatial dimensionality, ODT achieves major cost reductions compared to three-dimensional (3D) simulations. A comparison to recent direct numerical simulation (DNS) data at moderate Reynolds number (Re = u∞/v0 = 333, where u∞ and v0 are the free stream and suction velocity, respectively) suggests that theODT model is capable of reproducing several velocity statistics, i.e.mean velocity and turbulent kinetic energy budgets, while peak turbulent stresses are under-estimated by ODT. Variation of the Reynolds number in the range Re ∈ [333, 400, 500, 1000] shows that ODT can reproduce various trends observed as a result of increased suction in turbulent asymptotic suction boundary layers, i.e. the reduction of Reynolds stresses and enhanced skin friction. While up to Re = 500 our results can be directly compared to recent LES data, the simulation at Re = 1000 is currently not feasible through full 3D simulations, hence ODTmay assist the design of future DNS or LES simulations at larger Reynolds numbers. Y1 - 2017 SN - 1468-5248 VL - 18 IS - 10 SP - 899 EP - 928 ER - TY - GEN A1 - Movaghar, Amirreza A1 - Linne, Mark A1 - Oevermann, Michael A1 - Meiselbach, Falko T. A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - Numerical investigation of turbulent-jet primary breakup using One-Dimensional Turbulence T2 - International Journal of Multiphase Flow N2 - Primary breakup to form droplets at liquid surfaces is an important fundamental process to study as it determines the initial properties of the dispersed phase, which affect mixing rates, secondary breakup, droplet collisions, and flow separation within the dispersed flow region. Primary breakup can be regarded as one of the least developed model components for simulating and predicting liquid jet breakup. How- ever, it is of paramount importance in many technical applications, e.g. fuel injection in engines and spray painting. This paper presents a numerical investigation of primary breakup of a turbulent liquid jet in still air at standard conditions using the one-dimensional turbulence (ODT) modeling framework. ODT is a stochastic model that simulates turbulent flow evolution along a notional 1D line of sight by applying instantaneous maps to represent the effect of individual turbulent eddies on property profiles. An important feature of ODT is the resolution of all relevant scales, both temporal and spatial. The restriction to one spatial dimension in ODT permits affordable high resolution of interfacial and single-phase property gradients, which is key to capturing the local behavior of the breakup process and allows simulations at high Reynolds and Weber numbers that are currently not accessible to direct numerical simulations (DNS). This paper summarizes our extensions of the ODT model to simulate geometrically simple jet breakup problems, including representations of Rayleigh wave breakup, turbulent breakup, and shear-driven breakup. Each jet breakup simulation consists of a short temporal channel section to initialize a turbulent velocity profile at the nozzle exit followed by an adjacent jet section. The simulations are carried out for jet exit Reynolds number of 11,500, 23,000, 46,000 and 92,000 while the Weber number is varied within the range 102–107. We present results on breakup statistics including spatial locations of droplet release, droplet sizes and liquid core length. The results on primary breakup are compared to experimental results and models. Y1 - 2017 SN - 1879-3533 VL - 89 SP - 241 EP - 254 ER - TY - GEN A1 - Schmidt, Heiko A1 - Mellado, Juan Pedro A1 - Stevens, Bjorn T1 - Wind Shear and Buoyancy Reversal at the Top of Stratocumulus T2 - Journal of the atmospheric sciences N2 - A numerical experiment is designed to study the interaction at the stratocumulus top between a mean vertical shear and the buoyancy reversal due to evaporative cooling, without radiative cooling. Direct numerical simulation is used to eliminate the uncertainty introduced by turbulence models. It is found that the enhancement by shear-induced mixing of the turbulence caused by buoyancy reversal can render buoyancy reversal comparable to other forcing mechanisms. However, it is also found that (i) the velocity jump across the capping inversion Du needs to be relatively large and values of about 1ms21 that are typically associated with the convective motions inside the boundary layer are generally too small and (ii) there is no indication of cloud-top entrainment instability. To obtain these results, parameterizations of the mean entrainment velocity and the relevant time scales are derived from the study of the cloud-top vertical structure. Two overlapping layers can be identified: a background shear layer with a thickness (1/3)(Du)2/Db, where Db is the buoyancy increment across the capping inversion and a turbulence layer dominated by free convection inside the cloud and by shear production inside the relatively thin overlap region. As turbulence intensifies, the turbulence layer encroaches into the background shear layer and defines thereby the entrainment velocity. Particularized to the first research flight of the Second Dynamics andChemistry of theMarine Stratocumulus (DYCOMS II) field campaign, the analysis predicts an entrainment velocity of about 3mms21 after 5–10 min—a velocity comparable to the measurements and thus indicative of the relevance of mean shear in that case. Y1 - 2014 SN - 1520-0469 SN - 0022-4928 VL - 71 IS - 3 SP - 1040 EP - 1057 ER - TY - CHAP A1 - Klein, Marten A1 - Schmidt, Heiko A1 - Lignell, David O. T1 - Map-based modelling of high-Rayleigh-number turbulent convection in planar and spherical confinements T2 - Conference on Modelling Fluid Flow (CMFF’18), The 17th International Conference on Fluid Flow Technologies Budapest, Hungary, September 4-7, 2018 N2 - High-Rayleigh-number (high-Ra) turbulent convection is studied in planar and spherical confinement geometries using the One-Dimensional turbulence (ODT) model. ODT uses stochastic mapping events to model the effect of turbulent stirring along a representative line through the turbulent flow. Here, a new implementation of ODT is used which includes radial transport, buoyancy, and position-dependent gravity. Model parameters are optimised for air in a planar confinement with Ra = 3 x 10¹⁰ . The thermal and viscous boundary layers are found in very good agreement with reference data, especially in the vicinity of the wall, but also towards the bulk. In spherical geometry, the same model parameters yield systematically thicker boundary layers compared to the references. This was observed for various radius ratios, gravity profiles and Rayleigh numbers. Nevertheless, the bulk temperature and the asymmetry of the inner and outer boundary layers are captured by ODT. The results obtained suggests that ODT is mainly applicable for Ra ̰̰> 10⁷, and that optimal model parameters depend on the radius ratio. Y1 - 2018 UR - https://www.researchgate.net/publication/323292728 ER - TY - CHAP A1 - Rakhi, Rakhi A1 - Schmidt, Heiko T1 - A stochastic approach to investigate the incompressible temporally developing turbulent boundary layer T2 - Conference on Modelling Fluid Flow (CMFF’18), The 17th International Conference on Fluid Flow Technologies Budapest, Hungary, September 4-7, 2018 N2 - In the present study, we focus on a new application of the One-Dimensional Turbulence (ODT) Medina Méndez model to a temporally developing turbulent boundary layer. Due to dimensionality reduction in ODT, this model achieves major cost reductions as compared to full 3D simulations and is, thus, able to explore large parameter regimes. The model is fully and deterministically resolved for the diffsion effcts along a 1-Medina Méndez D domain, while the turbulent advection effects are represented by means of mapping events. Here, we apply the model for the first time to incompressible temporally developing turbulent boundary layers and compare our results to DNS [1]. We use no-slip and impermeable boundary conditions at the top and the bottom wall, respectively. To trigger the transition in the present study, uniform velocity is provided at the bottom wall for different bulk Reynolds numbers ( for Reb = 500, 1500, 1000, 2000). We compare the velocity statistics i.e. mean, root mean square and cross stresses to the recent DNS data. The comparison suggests that ODT is capable to reproduce several DNS velocity statistics which makes it an interesting tool to investigate higher Reynolds numbers as well as passive and active scalars in the future. Y1 - 2018 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Rakhi_2018_CMFF_paper_final.pdf ER - TY - CHAP A1 - Starick, Tommy A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - One-Dimensional Turbulence simulations for reactive flows in open and closed systems T2 - Conference on Modelling Fluid Flow (CMFF’18), The 17th International Conference on Fluid Flow Technologies Budapest, Hungary, September 4-7, 2018 N2 - The One-Dimensional Turbulence (ODT) model is applied to reactive flows in open and closed systems represented by a lifted jet flame in a vitiated coflow, and a constant volume autoignition configuration, respectively. ODT is a one-dimensional model for turbulent flow simulations, which uses a stochastic formulation to represent the effcts of turbulent advection. Diffusion and reaction effcts along the ODT domain are considered by deterministic evolution equations. This work is an effort to verify the applicability and effiency of the model for open and closed systems. In the open system case, ODT results are compared against experimental results of a lifted methane/air jet flame detailed in the work of Cabra et al. [1]. In the closed system case, a periodic, constant volume domain is used to investigate the sensitivity of the ignition evolution to initial temperature and composition inhomogeneities of a lean n-heptane/air mixture. In the latter context, ODT results are compared to DNS results from Luong et al. [2]. Results for the jet and constant volume configuration show a reasonable match with the experimental and DNS data, considering the reduced order of the model and the underlying assumptions for each case. At the jet configuration, a dependence of the flame evolution on the turbulence intensity parameter can be seen. For the closed system, initial temperature and composition inhomogeneities allow a mitigation of the undesirable rapid pressure rise. Y1 - 2018 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_2018_cmff_final_after_review.pdf ER - TY - CHAP A1 - Sharma, Sparsh A1 - Sarradj, Ennes A1 - Schmidt, Heiko T1 - Low-Fidelity Stochastic Approach for Airfoil-Turbulence Interaction Noise T2 - Fortschritte der Akustik - DAGA 2018, 44. Jahrestagung für Akustik, 19.-22. März 2018 in München Y1 - 2018 UR - https://www-docs.b-tu.de/fg-akustik/public/veroeffentlichungen/sharma_stochastic_daga2018.pdf SP - 1184 EP - 1187 PB - Deutsche Gesellschaft für Akustik CY - Berlin ER - TY - CHAP A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Towards numerical simulation of the ultimate state of convection using one-dimensional turbulence modeling T2 - International Conference on Rayleigh Bénard Convection, May 14-18, Enschede, The Netherlands, abstracts Y1 - 2018 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2018_rbc_abstract.pdf ER - TY - CHAP A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Stochastic Modeling of Passive Scalar Transport in Turbulent Channel Flows at High Schmidt Numbers T2 - 10th International Symposium on Turbulence and Shear Flow Phenomena (TSFP10), Chicago, USA, July, 2017 Y1 - 2017 UR - http://tsfp10.org/TSFP10_program/2/368.pdf ER - TY - CHAP A1 - Fragner, Moritz M. A1 - Schmidt, Heiko T1 - Investigating Asymptotic Suction Boundary Layers using a One-Dimensional Stochastic Turbulence Modeling Approach T2 - 10th International Symposium on Turbulence and Shear Flow Phenomena (TSFP10), Chicago, USA, July, 2017 Y1 - 2017 UR - http://www.tsfp-conference.org/proceedings/2017/2/132.pdf ER - TY - CHAP A1 - Pupo Sá da Costa, Pedro A1 - Schmidt, Heiko T1 - Towards a hybrid turbulent mixing model based on hierarchical parcel-swapping and one-dimensional turbulence T2 - 89th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 19-23, 2018 Munich, Germany, Book of abstracts N2 - One-dimensional turbulence (ODT) based models are able to generate good results for canonical flow problems compared to Direct Numerical Simulations. ODT has been successfully imple- mented as a sub-grid scale model for LES problems (ODTLES) delivering promising results. However, due to the computational cost of the ODT model in this scope, there is a need for an even faster model for real world parameter regimes. The Hierarchical Parcel Swapping (HiPS) algorithm used in combination with the ODT model to simulate a channel flow recently provided results with an acceptable quality in a fraction of the time of an ODT simulation. HiPS uses a binary tree to define the fluid domain, and stochastic eddy events are sampled in this tree. A local instantaneous and complete mixing of the cells is performed when an eddy event happens at the Kolmogorov scale. The biggest limitation of this model is that the viscosity of the solution is implicitly defined by the number of cells in a mesh. A more complex mixing model is introduced in order to introduce the viscosity of the flow as an explicit variable of the problem, providing a more versatile implementation of HiPS-ODT. This version of HiPS-ODT will serve to provide a computationally cheaper alternative for the ODT model, e.g. to be used in areas of less activity in 3D ODTLES flow simulations. Y1 - 2018 UR - http://jahrestagung.gamm-ev.de/images/2018/book_of_abstracts.pdf SP - S. 285 ER - TY - CHAP A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - One-Dimensional Turbulence investigation of incompressible and low Mach number variable density pipe-flow T2 - 89th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 19-23, 2018 Munich, Germany, Book of abstracts Y1 - 2018 UR - http://jahrestagung.gamm-ev.de/images/2018/book_of_abstracts.pdf SP - 285 EP - 286 PB - GAMM ER - TY - CHAP A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Investigating the Reynolds number dependency of the scalar transfer to a wall using a stochastic turbulence model T2 - 89th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 19-23, 2018 Munich, Germany, Book of abstracts Y1 - 2018 UR - http://jahrestagung.gamm-ev.de/images/2018/book_of_abstracts.pdf SP - S. 287 PB - GAMM ER - TY - CHAP A1 - Klein, Marten A1 - Schmidt, Heiko T1 - On Turbulent Scalar Transport at Very High Schmidt Numbers Using a Stochastic Modeling Appro T2 - 88th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 6-10, 2017 Weimar, Germany, Book of abstacts Y1 - 2017 UR - https://www.tu-ilmenau.de/fileadmin/media/analysis/trunk/170304_BoA_GAMM_2017.pdf SP - 357 EP - 358 PB - GAMM ER - TY - CHAP A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - Application of ODT to constant volume autoignition problems T2 - 88th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 6-10, 2017 Weimar, Germany, Book of abstracts Y1 - 2017 UR - https://www.tu-ilmenau.de/fileadmin/media/analysis/trunk/170304_BoA_GAMM_2017.pdf SP - S. 360 PB - GAMM ER - TY - CHAP A1 - Fragner, Moritz M. A1 - Schmidt, Heiko T1 - Investigating Asymptotic Suction Boundary Layers using a One-Dimensional Stochastic Turbulence Model T2 - 88th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 6-10, 2017 Weimar, Germany, Book of abstracts Y1 - 2017 UR - https://www.tu-ilmenau.de/fileadmin/media/analysis/trunk/170304_BoA_GAMM_2017.pdf SP - S. 361 PB - GAMM ER - TY - CHAP A1 - Schmidt, Heiko T1 - Map-based stochastic turbulence modeling T2 - 88th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 6-10, 2017 Weimar, Germany, Book of abstracts Y1 - 2017 UR - https://www.tu-ilmenau.de/fileadmin/media/analysis/trunk/170304_BoA_GAMM_2017.pdf SP - 425 EP - 426 PB - GAMM ER - TY - GEN A1 - Glawe, Christoph A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - IMEX based Multi-Scale Time Advancement in ODTLES, T2 - Zeitschrift für angewandte Mathematik und Mechanik KW - ODTLES Y1 - 2018 U6 - https://doi.org/10.1002/zamm.201800098 SN - 1521-4001 VL - 98 IS - 11 SP - 1907 EP - 1923 ER - TY - GEN A1 - Lignell, David O. A1 - Lansinger, Victoria B. A1 - Medina Méndez, Juan Ali A1 - Klein, Marten A1 - Kerstein, Alan R. A1 - Schmidt, Heiko A1 - Fistler, Marco A1 - Oevermann, Michael T1 - One-dimensional turbulence modeling for cylindrical and spherical flows: model formulation and application T2 - Theoretical and Computational Fluid Dynamics N2 - The one-dimensional turbulence (ODT) model resolves a full range of time and length scales and is computationally efficient. ODT has been applied to a wide range of complex multi-scale flows, such as turbulent combustion. Previous ODT comparisons to experimental data have focused mainly on planar flows. Applications to cylindrical flows, such as round jets, have been based on rough analogies, e.g., by exploiting the fortuitous consistency of the similarity scalings of temporally developing planar jets and spatially developing round jets. To obtain a more systematic treatment, a new formulation of the ODT model in cylindrical and spherical coordinates is presented here. The model is written in terms of a geometric factor so that planar, cylindrical, and spherical configurations are represented in the same way. Temporal and spatial versions of the model are presented. A Lagrangian finite-volume implementation is used with a dynamically adaptive mesh. The adaptive mesh facilitates the implementation of cylindrical and spherical versions of the triplet map, which is used to model turbulent advection (eddy events) in the one-dimensional flow coordinate. In cylindrical and spherical coordinates, geometric stretching of the three triplet map images occurs due to the radial dependence of volume, with the stretching being strongest near the centerline. Two triplet map variants, TMA and TMB, are presented. In TMA, the three map images have the same volume, but different radial segment lengths. In TMB, the three map images have the same radial segment lengths, but different segment volumes. Cylindrical results are presented for temporal pipe flow, a spatial nonreacting jet, and a spatial nonreacting jet flame. These results compare very well to direct numerical simulation for the pipe flow, and to experimental data for the jets. The nonreacting jet treatment overpredicts velocity fluctuations near the centerline, due to the geometric stretching of the triplet maps and its effect on the eddy event rate distribution. TMB performs better than TMA. A hybrid planar-TMB (PTMB) approach is also presented, which further improves the results. TMA, TMB, and PTMB are nearly identical in the pipe flow where the key dynamics occur near the wall away from the centerline. The jet flame illustrates effects of variable density and viscosity, including dilatational effects. KW - Cylindrical ODT Y1 - 2018 U6 - https://doi.org/10.1007/s00162-018-0465-1 SN - 0935-4964 SN - 1432-2250 VL - 32 IS - 4 SP - 495 EP - 520 ER - TY - GEN A1 - Starick, Tommy A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - One-Dimensional Turbulence simulations for reactive flows in open and closed systems T2 - Technische Mechanik Y1 - 2019 U6 - https://doi.org/10.24352/UB.OVGU-2019-015 VL - 39 IS - 1 SP - 162 EP - 174 ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - One‐dimensional turbulence investigation of incompressible and low Mach number variable density pipe‐flow T2 - Proceedings in Applied Mathematics and Mechanics : PAMM KW - ODT KW - pipe flow Y1 - 2018 U6 - https://doi.org/10.1002/pamm.201800090 SN - 1617-7061 VL - 18 IS - 1 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Schmidt, Heiko T1 - Investigating incompressible temporally developing turbulent boundary layers using One‐Dimensional Turbulence T2 - Proceedings in applied mathematics and mechanics KW - ODT, boundary layer Y1 - 2018 U6 - https://doi.org/10.1002/pamm.201800214 SN - 1617-7061 VL - 18 IS - 1 ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Investigating the Reynolds number dependency of the scalar transfer to a wall using a stochastic turbulence model T2 - Proceedings in applied mathematics and mechanics : PAMM Y1 - 2018 U6 - https://doi.org/10.1002/pamm.201800238 SN - 1617-7061 VL - 18 IS - 1 ER - TY - GEN A1 - Sá da Costa, Pedro P. A1 - Schmidt, Heiko T1 - Towards a hybrid turbulent mixing model based on hierarchical parcel-swapping and one-dimensional turbulence T2 - Proceedings in applied mathematics and mechanics Y1 - 2018 U6 - https://doi.org/10.1002/pamm.201800231 SN - 1617-7061 VL - 18 IS - 1 ER - TY - CHAP A1 - Medina Méndez, Juan Ali A1 - Glawe, Christoph A1 - Starick, Tommy A1 - Schöps, Mark Simon A1 - Schmidt, Heiko T1 - IMEX-ODTLES: A multi-scale and stochastic approach for highly turbulent flows T2 - 90th Annual Meeting of the International Association of Applied Mathematics and Mechanics February 18-22, 2019 Vienna, Austria, Abstract book Y1 - 2019 UR - https://jahrestagung.gamm-ev.de/images/2019/Photos/GAMM2019_BookofAbstracts.pdf SN - 978-3-903024-84-7 PB - TU-Verlag CY - Wien ER - TY - CHAP A1 - Starick, Tommy A1 - Schmidt, Heiko T1 - Hierarchical parcel swapping: an efficient mixing model for turbulent reactive flows T2 - 90th Annual Meeting of the International Association of Applied Mathematics and Mechanics February 18-22, 2019 Vienna, Austria, Abstract book Y1 - 2019 UR - https://jahrestagung.gamm-ev.de/images/2019/Photos/GAMM2019_BookofAbstracts.pdf SN - 978-3-903024-84-7 PB - TU-Verlag CY - Wien ER - TY - GEN A1 - Fragner, Moritz M. A1 - Schmidt, Heiko T1 - Investigating Asymptotic Suction Boundary Layers using a One-Dimensional Stochastic Turbulence Model T2 - Proceedings in applied mathematics and mechanics : PAMM Y1 - 2017 UR - https://onlinelibrary.wiley.com/doi/pdf/10.1002/pamm.201710288 U6 - https://doi.org/10.1002/pamm.201710288 SN - 1617-7061 VL - 17 IS - 1 SP - 637 EP - 638 ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Stochastic Modeling of Turbulent Scalar Transport at Very High Schmidt Numbers T2 - Proceedings in applied mathematics and mechanics : PAMM Y1 - 2017 UR - https://onlinelibrary.wiley.com/doi/pdf/10.1002/pamm.201710289 U6 - https://doi.org/10.1002/pamm.201710289 SN - 1617-7061 VL - 17 IS - 1 SP - 639 EP - 640 ER - TY - GEN A1 - Klein, Marten A1 - Lignell, David O. A1 - Schmidt, Heiko T1 - Map-Based Modeling of Turbulent Convection: Application of the One-Dimensional Turbulence Model to Planar and Spherical Geometries KW - turbulent convection KW - stochastic modeling KW - boundary layer Y1 - 2018 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_poster_rbc18.pdf UR - https://www.researchgate.net/publication/325155414_Map-Based_Modeling_of_Turbulent_Convection_Application_of_the_One-Dimensional_Turbulence_Model_to_Planar_and_Spherical_Geometries ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Map-based Modeling of Turbulent Boundary Layers Subject to Rotation and Stratification KW - boundary layers KW - stochastic modeling KW - rotating flows KW - thermal convection KW - turbulence Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_poster_lesHouches19.pdf ER - TY - GEN A1 - Klein, Marten A1 - Zenker, Christian A1 - Schmidt, Heiko T1 - Small-scale resolving simulations of the turbulent mixing in confined planar jets using one-dimensional turbulence T2 - Chemical Engineering Science Y1 - 2019 SN - 0009-2509 VL - 204 SP - 186 EP - 202 ER - TY - GEN A1 - Sharma, Sparsh A1 - Geyer, Thomas A1 - Sarradj, Ennes A1 - Schmidt, Heiko T1 - Numerical investigation of noise generation by rod-airfoil configuration using DES (SU2) and the FW-H analogy T2 - 25th AIAA/CEAS Aeroacoustics Conference 2019, Delft, The Netherlands, 20 - 24 May 2019, (AIAA 2019-2400) KW - airfoil noise KW - computational aeroacoustics KW - cylinder noise KW - detached eddy simulatio KW - ffowcs-williams hawkings KW - rod-airfoil Y1 - 2019 UR - https://arc.aiaa.org/doi/10.2514/6.2019-2400 U6 - https://doi.org/10.2514/6.2019-2400 SP - 1 EP - 17 ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Investigating the skin friction drag across electrolytes and electrical fields using one-dimensional turbulence modeling T2 - European Drag Reduction and Flow Control Meeting, EDRFCM 2019, March 26-29 2019, Bad Herrenalb, Germany KW - electrohydrodynamic flows KW - Couette flow KW - turbulence modeling Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2019_Klein+Schmidt_ODT_EHD_Couette_EDRFCM19.pdf UR - http://www.edrfcm.science/index.php/program SP - 1 EP - 2 ER - TY - GEN A1 - Klein, Marten A1 - Lignell, David O. A1 - Schmidt, Heiko T1 - Stochastic modeling of temperature and velocity statistics in spherical-shell convection T2 - Geophysical Research Abstracts, Vol. 21, EGU2019-2220 KW - turbulent convection KW - turbulence modeling KW - spherical shell Y1 - 2019 UR - https://meetingorganizer.copernicus.org/EGU2019/EGU2019-2220.pdf ER - TY - GEN A1 - Schmidt, Heiko A1 - Klein, Marten T1 - Simulating neutrally and stably stratified turbulent Ekman flows with a stochastic turbulence model T2 - Proc. of the 17th European Turbulence Conference (ETC17), 3-6 September 2019, Torino, Italy KW - turbulent boundary layer KW - turbulence modeling KW - Coriolis effects KW - stratification effects Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2019_etc.pdf UR - http://www.etc17.it/ ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Investigating Rayleigh-Bénard convection at low Prandtl numbers using one-dimensional turbulence modeling T2 - Proc. of the 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP11), Southampton, UK, July 30 to August 2, 2019 KW - turbulent convection KW - turbulence modeling KW - low Prandtl number KW - high Rayleigh number Y1 - 2019 UR - http://www.tsfp-conference.org/proceedings/2019/14.pdf ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Investigating thermal convection at low Prandtl numbers using one-dimensional turbulence KW - turbulent convection KW - turbulence modeling KW - low Prandtl number KW - high Rayleigh number Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2019_poster_tsfp11_evince-print.pdf N1 - Poster shown at 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP11), 30 July - 2 August 2019, Southampton, UK ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - The transition to the ultimate regime of thermal convection from a stochastic one-dimensional turbulence perspective T2 - arXiv KW - Rayleigh-Bénard convection KW - turbulence modeling KW - low Prandtl number KW - turbulent transitions KW - heat transfer Y1 - 2019 UR - https://arxiv.org/abs/1906.06621 SP - 1 EP - 11 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Klein, Marten A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - One-dimensional turbulence modelling of incompressible temporally developing turbulent boundary layers with comparison to DNS T2 - Journal of Turbulence N2 - The incompressible temporally developing turbulent boundary layer (TBL) is analysed using the map-based stochastic one-dimensional turbulence (ODT) model. The TBL is a canonical flow problem, which is, in the present study, formed by a planar moving wall and a free stream at rest. An understanding of this idealised flow is of fundamental relevance for the numerical analysis of turbulent boundary-layer-type flows. In the present ODT simulations, the flow variables are resolved on all scales along a wall-normal, one-dimensional domain. These variables are evolved by a deterministic and a stochastic process. The latter models the effect of turbulent advection and pressure fluctuations, whereas the former represents molecular diffusion. The model is appropriate for high Reynolds numbers for which the turbulence field exhibits a broad range of scales and is notionally featureless. We show that ODT is able to capture salient features of the TBL by comparing the various statistics with available reference direct numerical simulation (DNS) results for different bulk Reynolds numbers in the range 250 ≤ Reb ≤ 2000 using fixed model parameters. The influence of the model parameters is analysed for Reb = 1000 and optimal parameter values are provided. The results discussed in this paper suggest that ODT is an economical and reasonably accurate approach for the simulation of transient turbulent boundary-layer-type flows. KW - one-dimensional turbulence KW - stochastic modeling KW - turbulent boundary layers Y1 - 2019 U6 - https://doi.org/10.1080/14685248.2019.1674859 SN - 1468-5248 VL - 20 IS - 8 SP - 506 EP - 543 ER - TY - GEN A1 - Starick, Tommy A1 - Schmidt, Heiko T1 - Hierarchical Parcel Swapping: An efficient mixing model for turbulent reactive flows T2 - Proceedings in Applied Mathematics and Mechanics N2 - Hierarchical Parcel‐Swapping (HiPS) developed by A.R. Kerstein [J. Stat. Phys. 153, 142‐161 (2013)] is a computationally efficient and novel model for the effects of turbulence on time‐evolving, diffusive scalar fields. The characteristic feature of HiPS is the interpretation of the one‐dimensional flow domain or a state space as a binary tree structure. Every tree level corresponds to a specific length and time scale, which is based on a turbulence inertial range scaling. The state variables reside at the base of the tree and are interpreted as fluid parcels. The effects of turbulent advection are represented by stochastic swaps of sub‐trees at rates determined by turbulent time scales associated with the sub‐trees. The mixing of adjacent fluid parcels is done at rates consistent with the prevailing diffusion time scales. In this work, we investigate the influence of turbulent time scale variations on an isothermal series‐parallel reaction scheme. The production of a desired chemical species is evaluated by means of a defined selectivity and is strongly affected by the underlying mixing time scales. Y1 - 2019 U6 - https://doi.org/10.1002/pamm.201900492 SN - 1617-7061 VL - 19 SP - 1 EP - 2 ER - TY - GEN A1 - Starick, Tommy A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - Towards a dynamic model adaptive combustion closure using LEM, ODT, and HiPS T2 - 17th International Conference on Numerical Combustion, May 6-8, 2019, Aachen, Germany, Book of Abstracts N2 - The computational cost of Direct Numerical Simulations (DNS) that resolve all scales rises with the cube of the Reynolds numberand is currently not feasible for real world applications. Large Eddy Simulations (LES) overcome this limitation by only resolving the large scale effects and completely model the small scaleeffects. This results in a strong dependence of the accuracy onthe chosen subgrid-scale model. The model adaptivity concept discussed in [Schmidt et al., ICDERS, 2007] dynamically uses different Linear Eddy Model (LEM) types [Kerstein, LEM, 1988] for stochastic closure to model the turbulent flame speed of apremixed flame within LES. In the talk, we will first summarize the progress of our group on One Dimensional Turbulence (ODT) [Kerstein, ODT, 1999] and Hierarchical Parcel Swapping (HiPS) [Kerstein, HiPS, 2013] based on reactive stand-alone simulations, [Jozefik et al., Combust. Flame, 2015] [Jozefik et al., Combust. Flame, 2016] [Medina et al., Combust. Flame, 2018]. Second,we will sketch a possible combination of the model adaptivity concept [Schmidt et al., ICDERS, 2007] and recent efficient ODTLES implementations [Glawe et al., Z. Angew. Math. Mech.,2018] to dynamically use LEM, ODT and HIPS together inside ofLES solvers to simulate turbulent reactive flows. Y1 - 2019 UR - https://nc19.itv.rwth-aachen.de/bookOfAbstracts.pdf SP - 143 EP - 144 CY - Aachen ER - TY - GEN A1 - Starick, Tommy A1 - Lignell, David O. A1 - Schmidt, Heiko T1 - One-Dimensional Turbulence Modelling of a Lifted Methane/Air Jet Flame in a Vitiated Coflow T2 - Proc. of the 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP11)Southampton, UK, July 30 to August 2, 2019 N2 - The present preliminary numerical study investigates alifted methane/air jet flame in a vitiated coflow by meansof the map-based, stochastic One-Dimensional Turbulence(ODT) model. In the considered configuration, a jet flameissues from a central nozzle into a vitiated coflow of hotcombustion products from an array of lean H2/air flames.Centreline profiles for mixture fraction, temperature andmass fraction of O2and OH obtained from ODT simula-tions with a planar and cylindrical formulation are shownand compared to measurements from Cabraet al.(2005).Additionally, two-dimensional renderings of the jet flameand scatter plots of temperature versus mixture fraction andOH mass fraction versus mixture fraction are provided. Al-though the application of ODT for reactive flows in jet con-figurations is not novel, the chosen lifted jet flame in a vi-tiated coflow represents a challenge for the model. The ac-curate representation of the subtle interactions of the hotcoflow products with the cold unburnt jet flow are crucialfor the reaction and autoignition of the jet (Cabraet al.,2005). Considering the reduced order of the model and thetaken assumptions, the achieved results reasonably matchwith the measurement data. Y1 - 2019 UR - http://www.tsfp-conference.org/proceedings/2019/278.pdf ER - TY - GEN A1 - Starick, Tommy A1 - Lignell, David O. A1 - Schmidt, Heiko T1 - Towards a Simple Mixing Model for Passive Scalar Transport Using Hierarchical Parcel Swapping (HIPS) T2 - 17th European Turbulence Conference (ETC2019), 3-6 September 2019, Torino, IT KW - Hierarchical Parcel Swapping (HiPS) , passice scalar transport, mixing model Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_2019_ETC_Abstract_Starick.pdf UR - http://www.etc17.it/ ER - TY - GEN A1 - Starick, Tommy A1 - Medina Méndez, Juan Ali A1 - Klein, Marten A1 - Jozefik, Zoltan A1 - Schmidt, Heiko T1 - Zur jüngsten Entwicklung in der Modellierung von turbulenten Verbrennungsprozessen mittels ODT T2 - 29. Deutscher Flammentag, 17-18 September 2019, Bochum, DE N2 - Die vorliegende Arbeit befasst sich mit den jüngsten Entwicklungen und Anwendungen des One-Dimensional Turbulence (ODT) Modells auf reaktive Strömungen. Bei ODT handelt es sich um ein stochastisches und abbildungsbasiertes Turbulenzmodell zur Simulation von turbulenten Strömungen. In ODT wird das eindimensionale Rechengebiet als gedachte Linie durch das dreidimensionale Strömungsfeld verstanden, welches in Richtung des mittleren Gradienten einer Geschwindigkeit oder anderer skalarer Felder orientiert ist. Die Besonderheit von ODT liegt in der Modellierung der turbulenten Advektion durch stochastisch auftretende Wirbelereignisse. Die molekulare Diffusion und Reaktionskinetik entlang des ODT-Rechengebietes wird mittels sich zeitlich entwickelnder, deterministischer Erhaltungsgleichungen berücksichtigt und vollständig aufgelöst. In dieser Arbeit werden vorläufige ODT-Simulationsergebnisse von reaktiven Strömungen für jeweilsein offenes und ein geschlossenes System vorgestellt. Essentielle Vorarbeiten, die die Vermischungeines passiven Skalars in einer planaren Strahldüse untersuchen, werden ebenfalls gezeigt. Beim offenen System handelt es sich um eine Methan/Luft Freistrahl-Flamme in einer umgebenden Strömung aus heißen Verbrennungsgasen. Die Simulationsergebnisse werden zu Vergleichszweckenden Messungen von Cabra et al. gegenübergestellt. Beim geschlossenen System wird die Selbstzündung von mageren n-Heptan Gemischen bei niedrigen Temperaturen und komplexer Reaktionskinetik betrachtet. Hierbei werden die ODT-Ergebnisse mit den Resultaten aus einer Direkten Numerischen Simulation (DNS) verglichen. In den durchgeführten Studien konnte gezeigt werden, dass die mittels ODT erzeugten Statistiken eine beachtlich gute Übereinstimmung mit den Vergleichsdaten aufweisen. Im Hinblick auf die reduzierte Dimensionalität von ODT, die Qualitätder erzielten Ergebnisse und die erforderliche Rechenleistung, stellt ODT ein attraktives Modell zurSimulation von turbulenten und reaktiven Strömungen dar. KW - One-Dimensional Turbulence (ODT) , reaktive Strömungen Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_Abstract_Flammentag_19.pdf UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_2019_Flammentag19_Starick_Paper.pdf UR - http://www.leat.rub.de/index.php?do=Flammentag.html ER - TY - GEN A1 - Starick, Tommy A1 - Medina Méndez, Juan Ali A1 - Klein, Marten A1 - Jozefik, Zoltan A1 - Schmidt, Heiko T1 - Zur jüngsten Entwicklung in der Modellierung von turbulenten Verbrennungsprozessen mittels ODT Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_2019_Flammentag19_Starick_Poster.pdf ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - Application of ODT to constant volume autoignition problems T2 - Proceedings in Applied Mathematics and Mechanics N2 - The One-Dimensional Turbulence (ODT) model is applied to a constant volume configuration by means of a periodic, one-dimensional domain subject to randomized ensemble members with initial inhomogeneous temperature fields and homogeneous mass fraction profiles. The multidimensional turbulent interactions in the flow are modeled by the separate implementation of turbulent advection and the diffusion-reaction processes, neglecting the mean advection of the system. On one hand, turbulent advection is modeled by means of the eddy events defined within the framework of ODT; on the other hand, the diffusion-reaction system is solved by means of the Zero-Mach limit conservation equations discretized with a 1D Finite Volume Method (FVM). The treatment is specialized in this work to constant volume systems. Due to the inherent stiffness of the diffusion-reaction system, an operator splitting approach is also included in the formulation. Results for n-Heptane chemistry comprising the temporal evolution of the heat release rate, pressure and normalized density-weighted displacement speed are shown and compared to DNS results from Yoo et al. [Combust. Flame 158 (2011) 1727-1741], in terms of individual ensemble members and mean ensemble behavior. The results show that it is possible to obtain reasonably good results in comparison to the DNS if an appropriate set of initial conditions is used. Furthermore, it is shown that the model uncertainty is negligible in comparison to the ensemble standard deviation introduced by randomized initial conditions. Overall, this work introduces the framework for constant volume autoignition in ODT and shows its efficiency for complex chemistry simulations. Y1 - 2017 U6 - https://doi.org/10.1002/pamm.201710291 SN - 1617-7061 VL - 17 IS - 1 SP - 643 EP - 644 ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Glawe, Christoph A1 - Starick, Tommy A1 - Schöps, Mark Simon A1 - Schmidt, Heiko T1 - IMEX-ODTLES: A multi-scale and stochastic approach for highly turbulent flows T2 - Proceedings in Applied Mathematics and Mechanics N2 - The stochastic One-Dimensional Turbulence (ODT) model is used in combination with a Large Eddy Simulation (LES) approach in order to illustrate the potential of the fully coupled model (ODTLES) for highly turbulent flows. In this work, we use a new C++ implementation of the ODTLES code in order to analyze the computational performance in a classical incompressible turbulent channel flow problem. The parallelization potential of the model, as well as its physical and numerical consistency are evaluated and compared to Direct Numerical Simulations (DNSs). The numerical results show that the model is capable of reproducing a representative part of the DNS data at a cheaper computational cost. This advantage can be enhanced in the future by the implementation of a straightforward parallelization approach. Y1 - 2019 U6 - https://doi.org/10.1002/pamm.201900433 SN - 1617-7061 VL - 19 IS - 1 ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko A1 - Riebel, Ulrich T1 - Towards a One-Dimensional Turbulence Approach for Electrohydrodynamic Flows T2 - 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP11), Southampton, UK, July 30 to August 2, 2019 N2 - The One-Dimensional Turbulence model is modified in this work for its application to a classical electrohydrodynamic (EHD) problem. Being the first study case, this work is focused on the influence of electrostatic fields and space charge on the velocity field inside a wire-plate Electrostatic Precipitator (ESP) with one-way-coupling dynamics. The study case is an attempt to replicate velocity profiles and Turbulent Kinetic Energy (TKE) budgets obtained in the Direct Numerical Simulation (DNS) carried out by Soldati and Banerjee (1998). Qualitative trends are confirmed in preliminary ODT results, thus showing the potential of the stochastic ODT modeling approach for other types of EHD flows. Y1 - 2019 UR - http://www.tsfp-conference.org/proceedings/2019/265.pdf ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko A1 - Riebel, Ulrich T1 - Towards a One-Dimensional Turbulence Approach for Electrohydrodynamic Flows Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Medina_2019_TSFPPoster2019.pdf ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko A1 - Riebel, Ulrich T1 - Extension of the One-Dimensional Turbulence model towards electrohydrodynamic variable density flows T2 - 17th European Turbulence Conference (ETC2019), 3-6 September 2019, Torino, Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Medina_2019_ETC2019ODTEHDPlate.pdf CY - Turin ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Klein, Marten A1 - Schmidt, Heiko T1 - One-Dimensional Turbulence investigation of variable density effects due to heat transfer in a low Mach number internal air flow T2 - International Journal of Heat and Fluid Flow N2 - A novel spatial formulation of the One-Dimensional Turbulence (ODT) model is applied to a vertical pipe-flow with heat transfer, analogous to the Direct Numerical Simulation (DNS) performed by Bae et al. [Phys. Fluids 18, (075102) (2006)]. The framework presented here is an extension for radially confined domains of the cylindrical ODT spatial formulation for low Mach number flows with variable density. The variable density simulations for air (Prandtl number Pr = 0.71) are performed at an initial bulk Reynolds number Reb (DNS) = 6000 and Grashof number Gr (DNS) = 6.78*10^6. ODT results are presented for both the spatial formulation introduced in this work and the standard temporal formulation for cylindrical flows introduced by Lignell et al. [Theor. Comput. Fluid Dyn. 32, 4 (2018), pp. 495–520]. Streamwise bulk profiles and radial profiles at specific streamwise positions for the temporal and spatial formulations are in good agreement with the DNS results from Bae et al. For the present application, the spatial formulation yields physically better results in comparison to the temporal formulation. Overall, the findings in the original work of Bae et al. were corroborated with ODT. Although the framework proposed in this work is not a compressible framework and has some clear limitations regarding conservation properties, we suggest its use for future studies in the low Mach number variable density regime. Y1 - 2019 UR - http://www.sciencedirect.com/science/article/pii/S0142727X19301596 U6 - https://doi.org/10.1016/j.ijheatfluidflow.2019.108481 SN - 0142-727X SN - 1879-2278 VL - 80 ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko A1 - Lignell, David O. T1 - Application of the One-Dimensional Turbulence model to incompressible channel and pipe flow T2 - Publications Turbulent Reacting Flow Research Dr. David Lignell, Brigham Young University Y1 - 2019 UR - https://www.researchgate.net/publication/324604188_Application_of_the_One-Dimensional_Turbulence_model_to_incompressible_channel_and_pipe_flow/link/5ad8bda7a6fdcc29358659c4/download ER - TY - GEN A1 - Bacher, Christian A1 - Riebel, Ulrich A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - Nutzbarmachung des elektrischen Windes zum verbesserten Wärme und Stofftransport im Elektroabscheider T2 - ProcessNet 2020, Fachgruppe Gasreinigung N2 - Zur Förderung einer nachhaltigeren Wertschöpfungskette werden im Rahmen der Energiewende ständig neue Verfahren und Konzepte zu deren Umsetzung entwickelt. Eines dieser Konzepte befasst sich mit der Zusammenführung bislang entkoppelter Prozessschritte in Gasreinigungssystemen aus der Energie- und Anlagentechnik. Aus den daraus resultierenden Einsparungen bei den Investitionskosten profitieren nicht nur die klassischen Energieerzeugeuer und Produktionsanlagen in der chemischen Industrie, sondern es werden auch neue Anreize zur dezentralen Energieeinspeisung von kleineren und mittelständischen Unternehmen gesetzt. Elementarer Bestandteil dieser Gasreinigungssysteme sind häufig Elektroabscheider, welche weit verbreitet im Einsatz sind um Abgase von Stäuben bzw. Aerosolen zu befreien, oder um staubförmige Wertprodukte aus Gasströmungen abzuscheiden. Die in Elektroabscheidern prinzipbedingt vorhandenen elektro¬¬hydro¬dyna¬mischen Strömungen, auch als elektrischer Wind bezeichnet, sollen nun systematisch genutzt werden, um neben der Aerosolabscheidung gleichzeitig Aufgaben des Wärme- und Stoffaustauschs zu lösen. Inhalte der Untersuchungen Zur Validierung der Machbarkeit dieser neuen Techniken wurde der Einfluss des elektrischen Windes auf die turbulente Quervermischung, anhand des verbesserten Wärme- und Stofftransports, sowie des Druckverlusts im Rohrelektroabscheider getestet. Bei den Untersuchungen wurden unterschiedliche Strömungsgeschwindigkeiten, Elektrodengeometrien und Betriebsspannungen, sowie die Anwesenheit von Aerosol berücksichtigt. Ein Teil der Ergebnisse diente bereits als Validierungsgrundlage für numerische Simulationen mit einem neuartigen Turbulenzmodell [1]. [1] Medina, J., Schmidt, H., Riebel, U., Application of the one-dimensional turbulence model for electrohydrodynamic variable density flows, 17th European Turbulence Conference, 3-6 September 2019, Torino, Italy Y1 - 2020 UR - https://www.researchgate.net/publication/340363119_Nutzbarmachung_des_elektrischen_Windes_zum_verbesserten_Warme-und_Stofftransport_im_Elektroabscheider ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Bacher, Christian A1 - Schmidt, Heiko A1 - Riebel, Ulrich T1 - EHD-ODT: a stochastic turbulence model for the study of heat and mass transfer in wire-tube electrostatic precipitators T2 - Jahrestreffen der ProcessNet-Fachgruppen Computational Fluid Dynamics und Gasreinigung Y1 - 2020 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Medina_2020_ProcessNETConferenceAbstract.pdf PB - DECHEMA e.V. ER - TY - GEN A1 - Sharma, Sparsh A1 - Sarradj, Ennes A1 - Schmidt, Heiko T1 - Stochastic modelling of leading-edge noise in time-domain using vortex particles T2 - Journal of Sound and Vibration Y1 - 2020 U6 - https://doi.org/10.1016/j.jsv.2020.115656 SN - 0022-460X VL - Vol. 488 ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko T1 - The One-Dimensional Turbulence aspects of internal forced convective flows T2 - 14th World Congress on Computational Mechanics (WCCM XIV) ; 8th European Congress on Computational Methods in Applied Science and Engineering (ECCOMAS 2020) Y1 - 2020 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Medina_2020_ODTInternalForcedConvectiveFlows.pdf CY - Paris, France ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Stochastic modeling of passive scalars in turbulent channel flows T2 - Jahresbericht 2020 zum Band: Notes on Numerical Fluid Mechanics and Multidisciplinary Design - New Results in Numerical and Experimental Fluid Mechanics XIII KW - one-dimensional turbulence KW - passive scalar KW - channel flow Y1 - 2020 UR - https://www.dlr.de/as/Portaldata/5/Resources/dokumente/veranstaltungen/stab_workshop/STAB-Jahresbericht-2020.pdf VL - 2020 SP - 30 EP - 31 PB - Deutsche Strömungsmechanische Arbeitsgemeinschaft, STAB CY - Göttingen ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Towards a stochastic model for electrohydrodynamic turbulence with application to electrolytes T2 - Proceedings in Applied Mathematics and Mechanics N2 - We investigate turbulent Couette flows of dilute, weakly-conducting electrolytes by utilizing the stochastic one-dimensional turbulence (ODT) model. The flow is driven by relative motion of the top and bottom wall and affected by an electric field between these walls that is prescribed by a voltage difference. The electrolytes considered have zero bulk charge and consist of two ion species with the same mobility, valence, and initial concentration. The stochastic model predicts a decrease of the mean streamwise velocity when an external voltage is applied provided that both Schmidt (Sc) and Reynolds (Re) numbers are sufficiently large, that is, Sc > 30 for Re = 12000 investigated. The effect observed is relevant for flow control, but the mechanism awaits clarification. Present ODT results may help to develop this understanding or design laboratory experiments. KW - one-dimensional turbulence KW - electroconvection KW - EHD turbulence KW - Couette flow KW - electrolyte flow Y1 - 2020 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2020_EHD-Couette_PAMM.pdf U6 - https://doi.org/10.1002/pamm.202000128 VL - 2020 IS - 20 SP - 1 EP - 2 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Sharma, Sparsh A1 - Klein, Marten A1 - Schmidt, Heiko A1 - Sarradj, Ennes T1 - On a lower-order framework for jet noise prediction based on one-dimensional turbulence T2 - arXiv N2 - Noise prediction requires the resolution of relevant acoustic sources on all scales of a turbulent flow. High-resolution direct numerical and large-eddy simulation would be ideal but both are usually too costly despite developments in high performance computing. Lower-order modeling approaches are therefore of general interest. A crucial but standing problem for accurate predictive modeling is the estimation of missing noise from the modeled scales. In this paper we address this problem by presenting a novel lower-order framework that couples the one-dimensional turbulence model to the Ffowcs-Williams and Hawkings approach for prediction of the far-field noise of a subsonic turbulent round jet. KW - Ffowcs-Williams and Hawkings equation KW - jet noise KW - one-dimensional turbulence KW - turbulent mixing noise Y1 - 2020 UR - https://arxiv.org/abs/2010.11050 SP - 1 EP - 4 ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Predictive modeling of passive scalar transfer to a wall using stochastic one-dimensional turbulence T2 - arXiv N2 - Passive scalars in turbulent channel flows are investigated as canonical problem for heat and mass transfer in turbulent boundary-layer flows. The one-dimensional turbulence model is used to numerically investigate the Schmidt and Reynolds number dependence of the scalar transfer to a wall due to fluctuating wall-normal transport. First, the model is calibrated for low-order velocity statistics. After that, we keep the model parameters fixed and investigate low-order passive scalar statistics for a relevant Schmidt and Reynolds number range. We show that the model consistently predicts the boundary layer structure and the scaling regimes, for which it is close to asymptotic one-dimensional theory. KW - one-dimensional turbulence KW - passive scalar KW - turbulent channel flow KW - mass transfer coefficient KW - high Schmidt number Y1 - 2020 UR - https://arxiv.org/abs/2011.04818 ER - TY - GEN A1 - Schmidt, Heiko A1 - Medina Méndez, Juan Ali A1 - Klein, Marten T1 - EHD turbulence in channel flows with inhomogeneous electrical fields: a one-dimensional turbulence study T2 - 14th World Congress on Computational Mechanics (WCCM) ; ECCOMAS Congress 2020, 19–24 July 2020, Paris, France KW - EHD turbulence; channel flow; electrolyte flow; electrostatic precipitator; one-dimensional turbulence; stochastic modeling Y1 - 2020 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Schmidt_2020_EHD-channel-flows_WCCM-abstract.pdf UR - https://slideslive.com/38946214 U6 - https://doi.org/10.23967/wccm-eccomas.2020.131 ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Modeling one and two passive scalar mixing in turbulent jets using one-dimensional turbulence T2 - 14th World Congress on Computational Mechanics (WCCM) ; ECCOMAS Congress 2020, 19–24 July 2020, Paris, France KW - one-dimensional turbulence KW - passive scalar KW - turbulent mixing KW - turbulent jet Y1 - 2020 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2020_scalars_in_jets_WCCM-abstract.pdf UR - https://www.wccm-eccomas2020.org ER - TY - GEN A1 - Klein, Marten A1 - Lignell, David O. A1 - Schmidt, Heiko T1 - MS404: Map-based stochastic methods for accurate modeling of turbulent heat and mass transfer T2 - 14th World Congress on Computational Mechanics (WCCM XIV) ; 8th European Congress on Computational Methods in Applied Science and Engineering (ECCOMAS 2020), July 19–24, 2020, Paris, France KW - heat and mass transport KW - map-based stochastic modeling KW - turbulent mixing KW - convection KW - clouds Y1 - 2020 UR - https://www.wccm-eccomas2020.org/admin/Files/FileAbstract/a404.pdf ER - TY - GEN A1 - Klein, Marten A1 - Kerstein, Alan R. A1 - Schmidt, Heiko T1 - Stochastic modeling of transient boundary layers in high-Rayleigh-number thermal convection T2 - 25th International Congress of Theoretical and Applied Mechanics (ICTAM 20+1) N2 - One-dimensional turbulence (ODT) modeling is used to investigate the boundary layer in high-Rayleigh-number thermal convection for a notionally infinite horizontal layer of fluid. The model formulation distinguishes between turbulent advection, which is modeled by a stochastic process, and deterministic molecular diffusion to capture relevant vertical transport processes (including counter-gradient fluxes). For this study, statistical homogenization is applied to the two horizontal dimensions so that we use ODT as stand-alone tool. We show that the model yields mean and fluctuation temperature profiles that are in several respects consistent with available reference data. Furthermore, the profile of a surrogate for the fluctuation velocity is reminiscent of canonical wall turbulence. KW - one-dimensional turbulence KW - thermal convection KW - turbulent boundary layer Y1 - 2020 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2020_ODT-RBC_ICTAM20+1.pdf ER - TY - GEN A1 - Starick, Tommy A1 - Schmidt, Heiko T1 - Stochastic modeling of a lifted methane/air jet flame T2 - 14th World Congress on Computational Mechanics (WCCM XIV) ; 8th European Congress on Computational Methods in Applied Science and Engineering (ECCOMAS 2020), July 19–24, 2020, Paris, France Y1 - 2020 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_2020_WCCM_Abstract.pdf ER - TY - GEN A1 - Starick, Tommy A1 - Schmidt, Heiko T1 - Stochastische Modellierung einer Methan/Luft Freistrahl-Flamme mit detaillierter Chemie T2 - 30. Deutscher Flammentag, 28-29 September 2021, Hannover, DE Y1 - 2020 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_2020_Flammentag_Abstract.pdf ER - TY - GEN A1 - Starick, Tommy A1 - Lignell, David O. A1 - Schmidt, Heiko T1 - Stochastic Modeling of a Lifted Methane/Air Jet Flame with Detailed Chemistry T2 - 91th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 15-19, 2020 Kassel, DE Y1 - 2020 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Starick_2020_GAMM_Abstract.pdf ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - Transition to the ultimate regime in a stochastic model for thermal convection with internal sources Y1 - 2021 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_poster_ipam21.pdf CY - IPAM Workshop: Transport and Mixing in Complex and Turbulent Flows (CTF2021), University of California, Los Angeles, CA, USA ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Map-based stochastic methods for accurate modeling of turbulent transport: towards poly-dispersed engineering flows T2 - Jahrestreffen der ProcessNet Fachgruppen Mehrphasenstömung (MPH) und Computational Fluid Dynamics (CFD) Y1 - 2021 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Medina_2020_ODTProcessNet2021.pdf CY - Cottbus ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko A1 - Bacher, Christian A1 - Riebel, Ulrich T1 - Electrohydrodynamic‐enhanced internal pipe flows from a One‐Dimensional Turbulence perspective T2 - 91st Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM) Y1 - 2020 U6 - https://doi.org/10.1002/pamm.202000132 VL - 20 IS - 1 PB - Wiley ER - TY - GEN A1 - Rakhi, Rakhi A1 - Schmidt, Heiko T1 - Using a Stochastic One-Dimensional Turbulence model to study Incomporessible Spatially Developing Turbulent Boundary Layers T2 - Proc. of the 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP11), Southampton, UK, July 30 to August 2, 2019 Y1 - 2019 UR - http://www.tsfp-conference.org/proceedings/2019/273.pdf ER - TY - GEN A1 - Rakhi, Rakhi A1 - Schmidt, Heiko T1 - One-dimensional turbulence: application to incompressible spatially developing turbulent boundary layers T2 - Journal of Heat and Fluid Flow Y1 - 2020 U6 - https://doi.org/10.1016/j.ijheatfluidflow.2020.108626 SN - 0142-727X IS - 85 ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko A1 - Lignell, David O. T1 - Map-based modeling of high-Ra turbulent convection in planar and spherical geometries T2 - Conference on Modelling Fluid Flow 2018 (CMFF'18) N2 - Turbulent convection is important in many technological and geophysical applications. A model problem for such flows is Rayleigh-Bénard (RB) convection. The classical RB setup is a fluid- filled box with a heated bottom and cooled top. For geophysical applications, the spherical geometry of the confinement is sometimes important (e.g. in mantle convection). This is addressed by a spherical annulus configuration in which fluid is confined between an inner hot and an outer cold sphere. In this case, the gravity field is radial and its strength can also vary with the radius. Numerical simulations of RB convection are challenging because of the high Rayleigh numbers (Ra) observed in applications. 3-D direct simulations have been performed up to Ra ~ 10^(12), but even larger values of Ra are relevant. Hence modeling is needed if one wishes to increase the accessible Rayleigh number limit within the considerable future. The difficulty is that gradient-diffusion approaches do not allow for scale interactions, which can be crucial for the dynamics of the flow and the resulting heat transfer. In order to make such simulations feasible we make use of a different modeling strategy, the so-called One-Dimensional Turbulence (ODT). ODT resolves all scales of the flow along a notional line of sight, but reduces cost by assuming statistical homogeneity of the flow in the off-line directions. Along the line, turbulent advection is modeled by discrete mapping events, which mimic the effect of turbulent stirring. These events are stochastically sampled with highest probability where shear and buoyancy yield net available energy in analogy to real turbulence. In the talk, we evaluate ODT results against available reference data (e.g. flow statistics, heat transfer) using a new and fully adaptive version of ODT. This new version allows to simulate turbulent convection in spherical geometry. We address this by discussing the effects of radius ratio and radius-dependent gravity. KW - stochastic turbulence modeling KW - one-dimensional turbulence KW - heat transfer KW - high Rayleigh number KW - spherical shell convection KW - turbulent thermal convection Y1 - 2018 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_cmff18_abstract.pdf ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Investigating Rayleigh-Bénard convection at low Prandtl numbers using one-dimensional turbulence modeling T2 - Proc. of the 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP11), Southampton, UK, July 30 to August 2, 2019 N2 - We numerically investigate the heat transfer in turbulent Rayleigh–Bénard convection at two Prandtl numbers, Pr = 0.021 and 0.7, respectively. Small-scale resolving simulations up to the Rayleigh numbers Ra = 10^(13) (Pr = 0.021) and 10^(16) (Pr = 0.7) are made feasible by utilizing the stochastic, one-dimensional turbulence (ODT) model. Present ODT simulations exhibit effective Nusselt number Nu scalings of the form Nu ∼ Ra^γ. At low Rayleigh numbers, ODT yields a scaling exponent of γ = 0.29 (Pr = 0.021) and 0.32 (Pr = 0.7), respectively. Both values are systematically, but just slightly, overestimating available reference data. At high Rayleigh numbers, present ODT results exhibit an increase of the exponent to γ = 0.32 (Pr = 0.021) and 0.36 (Pr = 0.7), respectively. Our preliminary results suggest that ODT might be able to capture a transition from the classical to the ultimate state of convection in terms of (i) critical Rayleigh number and (ii) increase of γ. KW - stochastic turbulence modeling KW - one-dimensional turbulence KW - turbulent thermal convection KW - high Rayleigh number Y1 - 2019 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2019_tsfp11_v2.pdf SP - 1 EP - 3 ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Klein, Marten A1 - Schmidt, Heiko T1 - The One-Dimensional Turbulence Aspects of Internal Forced Convective Flows T2 - 14th WCCM-ECCOMAS Congress 2020 N2 - We present an overview of issues for the modeling of internal forced convective flows with the One-Dimensional Turbulence (ODT) model. Results of recent research as well as prospective research issues are presented for statistically streamwise homogeneous flows and streamwise inhomogeneous mixed convective flows. The results illustrate the capabilities of the model to evaluate and bring insight into a wide range of physical phenomena in the field of convective flows. Nonetheless, as a model, ODT is best suited for the evaluation of asymptotically turbulent flows, i.e., away from laminar regimes. KW - one-dimensional turbulence KW - stochastic turbulence modeling KW - turbulent drag KW - internal flow KW - heat transfer Y1 - 2021 UR - https://www.scipedia.com/public/Mendez_et_al_2021a U6 - https://doi.org/10.23967/wccm-eccomas.2020.338 SP - 1 EP - 12 PB - Scipedia ER - TY - GEN A1 - Klein, Marten A1 - Zenker, Christian A1 - Hertha, Katja A1 - Schmidt, Heiko T1 - Modeling One and Two Passive Scalar Mixing in Turbulent Jets Using One-Dimensional Turbulence T2 - 14th WCCM-ECCOMAS Congress 2020 N2 - Turbulent mixing of two passive scalars is investigated in a constant-property jets using stochastic one-dimensional turbulence (ODT). Scalars are separately injected by a central round and a surrounding annular jet that issue into a uniform co-flow of low velocity. These scalars are transported downstream and dispersed in radial direction by turbulent advection and molecular diffusion. The jet as well as the turbulent inflow are numerically simulated with ODT as stand-alone tool using a temporal (T-ODT) and spatial (S-ODT) formulation. We show that ODT captures key properties of the turbulent mixing for one scalar by performing individual scalar statistics and for two scalars by computation of joint probabilities. Some limitations of the one-dimensional modeling approach are also discussed. KW - one-dimensional turbulence KW - stochastic turbulence modeling KW - turbulent mixing KW - round jet KW - passive scalars Y1 - 2021 UR - https://www.scipedia.com/public/Klein_et_al_2021a U6 - https://doi.org/10.23967/wccm-eccomas.2020.205 SP - 1 EP - 12 PB - Scipedia ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Towards a stochastic model for electrohydrodynamic turbulence with application to electrolytes T2 - 91st Annual Meeting of GAMM 2020@21 N2 - We investigate turbulent electrohydrodynamic (EHD) Couette flows of dilute electrolytes and how they are affected by a prescribed electric field. In this canonical problem, molecular diffusion and electric drift currents can interact with turbulence which yields intricate dynamics down to the Kolmogorov and Batchelor scales that need to be resolved. The electrolytes considered have neutral bulk charge and consist of two independent, positive and negative, ion species with the same valence and mobility. The top wall of the set-up is moving and held at a different voltage relative to the bottom one. Resolution requirements and numerical feasibility are addressed by utilizing the stochastic one-dimensional turbulence (ODT) model as stand-alone tool in order to resolve all relevant scales of the flow for a dimensionally reduced setting. Deterministic diffusion and charge-carrier drift are directly resolved, whereas the effects of turbulent advection and pressure fluctuations are modeled by a stochastic process that operates along the wall-normal ODT domain. For the hydrodynamic and low Schmidt number EHD regime, ODT reasonably captures and extrapolates relevant leading-order boundary-layer properties of reference direct numerical simulations (DNS). For the high Schmidt number EHD regime, the model predicts notable interactions between turbulence and elektrokinetics only for large enough Reynolds numbers that manifests itself by a significant increase of the turbulent drag. Present ODT results suggests that the origin of this effect is related to the time-scale separation of convective versus electric drift and molecular transport processes transport across the boundary layer. In the talk, we will address the model formulation and its application to EHD Couette flow. Additionally, we will comment on the representation of electrokinetics and hydro-dynamics for the selected set-up. Finally, we will discuss the flow regimes in terms of skin friction drag and flow profiles with an eye also on electric variables and time scales. KW - one-dimensional turbulence KW - stochastic turbulence modeling KW - EHD turbulence KW - channel flow KW - electrolyte flow Y1 - 2021 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2021_elco_GAMM_abstract.pdf UR - https://hessenbox.uni-kassel.de/dl/fi226HzF3AJV3g4LFWM4fWE6/daily_program_2020.pdf?inline ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko T1 - Stochastic modeling of transient neutral and stably-stratified Ekman boundary layers T2 - 91st Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM) - PAMM, Proceedings in Applied Mathematics and Mechanics N2 - Turbulence is a transient phenomenon in atmospheric boundary layers. These transients occur often due to surface temperature variations (e.g. due to diurnal forcing) that directly influence the near-surface flow by local stratification effects. Relevant dynamical and transport processes occur on a scale of meters near the surface which is a standing challenge for numerical weather and climate prediction. Here we investigate neutral and stably-stratified Ekman flows as a canonical problem for the night-time atmospheric boundary layer over flat terrain. The set-up used consists of an incompressible fluid over a smooth horizontal no-slip wall in a rotating frame of reference. The bulk flow is in geostrophic balance and acts as momentum source. In the case of stable stratification, temperature is prescribed as sudden cooling on a fully-developed turbulent neutrally-stratified Ekman boundary layer. When the stratification is weak, the temperature behaves like a passive scalar, but when it is strong, turbulence may locally disappear. Transient simulations across a relevant range of Reynolds and Froude numbers are made feasible by utilizing the stochastic one-dimensional turbulence (ODT) model. ODT aims to resolve vertical (wall-normal) transport processes on all relevant scales for a one-dimensional domain. Deterministic molecular diffusion and Coriolis forces are directly resolved, whereas turbulent advection is modeled by a stochastic process. The model obeys several relevant physical principles as, for example, Richardson’s 1/4 law of stratified turbulence. Preliminary results suggest that the stand-alone model generally captures Reynolds (turbulence) and Froude number (stratification) effects when stratification is weak. For low Froude number (strong stratification), these results indicate that the model tends to overestimate turbulence effects near the surface unless stratification becomes so strong that near-surface turbulence is energetically prohibited. In the talk, we will address the model formulation and its application to Ekman flow. We will show and discuss model results for surface fluxes, boundary-layer profiles, and corresponding fluctuation statistics. In addition, we will discuss stratification effects and comment on their representation in the model. KW - one-dimensional turbulence KW - stochastic turbulence modeling KW - atmospheric boundary layer KW - rotating flow KW - stratified flow Y1 - 2021 UR - https://www-docs.b-tu.de/fg-stroemungsmodellierung/public/Klein_2021_Ekman_GAMM_abstract.pdf U6 - https://doi.org/10.1002/pamm.202000127 SN - 1617-7061 VL - 20 IS - 1 ER - TY - GEN A1 - Klein, Marten A1 - Schmidt, Heiko A1 - Kerstein, Alan R. T1 - Transition to the ultimate regime in a stochastic model for radiatively driven turbulent convection T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft - BPCPPDYSOE21 KW - stochastic turbulence modeling KW - turbulent thermal convection KW - one-dimensional turbulence KW - heat transfer Y1 - 2021 UR - https://www.dpg-verhandlungen.de/year/2021/conference/bpcppdysoe/part/dy/session/2/contribution/1?lang=en ER - TY - GEN A1 - Medina Méndez, Juan Ali A1 - Schmidt, Heiko A1 - Riebel, Ulrich T1 - Towards a One-Dimensional Turbulence Approach for Electrohydrodynamic Flows T2 - 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP11), Southampton, UK, July 30 to August 2, 2019 Y1 - 2019 UR - http://tsfp11.org/openconf/modules/request.php?module=oc_program&action=view.php&id=265&type=3&a= ER -