@misc{MedinaMendezSchmidtMaussetal., author = {Medina M{\´e}ndez, Juan Ali and Schmidt, Heiko and Mauß, Fabian and Jozefik, Zoltan}, title = {Constant volume n-Heptane autoignition using One-Dimensional Turbulence}, series = {Combustion and Flame}, volume = {190}, journal = {Combustion and Flame}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2017.12.015}, pages = {388 -- 401}, abstract = {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 …}, language = {en} } @inproceedings{KleinSchmidtLignell, author = {Klein, Marten and Schmidt, Heiko and Lignell, David O.}, title = {Map-based modelling of high-Rayleigh-number turbulent convection in planar and spherical confinements}, series = {Conference on Modelling Fluid Flow (CMFF'18), The 17th International Conference on Fluid Flow Technologies Budapest, Hungary, September 4-7, 2018}, booktitle = {Conference on Modelling Fluid Flow (CMFF'18), The 17th International Conference on Fluid Flow Technologies Budapest, Hungary, September 4-7, 2018}, pages = {8}, abstract = {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.}, language = {en} } @inproceedings{RakhiSchmidt, author = {Rakhi, Rakhi and Schmidt, Heiko}, title = {A stochastic approach to investigate the incompressible temporally developing turbulent boundary layer}, series = {Conference on Modelling Fluid Flow (CMFF'18), The 17th International Conference on Fluid Flow Technologies Budapest, Hungary, September 4-7, 2018}, booktitle = {Conference on Modelling Fluid Flow (CMFF'18), The 17th International Conference on Fluid Flow Technologies Budapest, Hungary, September 4-7, 2018}, pages = {8}, abstract = {In the present study, we focus on a new application of the One-Dimensional Turbulence (ODT) Medina M{\´e}ndez 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 M{\´e}ndez 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.}, language = {en} } @inproceedings{StarickMedinaMendezSchmidt, author = {Starick, Tommy and Medina M{\´e}ndez, Juan Ali and Schmidt, Heiko}, title = {One-Dimensional Turbulence simulations for reactive flows in open and closed systems}, series = {Conference on Modelling Fluid Flow (CMFF'18), The 17th International Conference on Fluid Flow Technologies Budapest, Hungary, September 4-7, 2018}, booktitle = {Conference on Modelling Fluid Flow (CMFF'18), The 17th International Conference on Fluid Flow Technologies Budapest, Hungary, September 4-7, 2018}, pages = {8}, abstract = {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.}, language = {en} } @inproceedings{SharmaSarradjSchmidt, author = {Sharma, Sparsh and Sarradj, Ennes and Schmidt, Heiko}, title = {Low-Fidelity Stochastic Approach for Airfoil-Turbulence Interaction Noise}, series = {Fortschritte der Akustik - DAGA 2018, 44. Jahrestagung f{\"u}r Akustik, 19.-22. M{\"a}rz 2018 in M{\"u}nchen}, booktitle = {Fortschritte der Akustik - DAGA 2018, 44. Jahrestagung f{\"u}r Akustik, 19.-22. M{\"a}rz 2018 in M{\"u}nchen}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik}, address = {Berlin}, pages = {1184 -- 1187}, language = {en} } @inproceedings{KleinSchmidt, author = {Klein, Marten and Schmidt, Heiko}, title = {Towards numerical simulation of the ultimate state of convection using one-dimensional turbulence modeling}, series = {International Conference on Rayleigh B{\´e}nard Convection, May 14-18, Enschede, The Netherlands, abstracts}, booktitle = {International Conference on Rayleigh B{\´e}nard Convection, May 14-18, Enschede, The Netherlands, abstracts}, pages = {1}, language = {en} } @inproceedings{PupoSadaCostaSchmidt, author = {Pupo S{\´a} da Costa, Pedro and Schmidt, Heiko}, title = {Towards a hybrid turbulent mixing model based on hierarchical parcel-swapping and one-dimensional turbulence}, series = {89th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 19-23, 2018 Munich, Germany, Book of abstracts}, booktitle = {89th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 19-23, 2018 Munich, Germany, Book of abstracts}, pages = {S. 285}, abstract = {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.}, language = {en} } @inproceedings{MedinaMendezSchmidt, author = {Medina M{\´e}ndez, Juan Ali and Schmidt, Heiko}, title = {One-Dimensional Turbulence investigation of incompressible and low Mach number variable density pipe-flow}, series = {89th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 19-23, 2018 Munich, Germany, Book of abstracts}, booktitle = {89th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 19-23, 2018 Munich, Germany, Book of abstracts}, publisher = {GAMM}, pages = {285 -- 286}, language = {en} } @inproceedings{KleinSchmidt, author = {Klein, Marten and Schmidt, Heiko}, title = {Investigating the Reynolds number dependency of the scalar transfer to a wall using a stochastic turbulence model}, series = {89th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 19-23, 2018 Munich, Germany, Book of abstracts}, booktitle = {89th Annual Meeting of the International Association of Applied Mathematics and Mechanics March 19-23, 2018 Munich, Germany, Book of abstracts}, publisher = {GAMM}, pages = {S. 287}, language = {en} } @misc{GlaweMedinaMendezSchmidt, author = {Glawe, Christoph and Medina M{\´e}ndez, Juan Ali and Schmidt, Heiko}, title = {IMEX based Multi-Scale Time Advancement in ODTLES,}, series = {Zeitschrift f{\"u}r angewandte Mathematik und Mechanik}, volume = {98}, journal = {Zeitschrift f{\"u}r angewandte Mathematik und Mechanik}, number = {11}, issn = {1521-4001}, doi = {10.1002/zamm.201800098}, pages = {1907 -- 1923}, language = {en} }