@inproceedings{MovagharLinneOevermannetal., author = {Movaghar, Amirreza and Linne, Mark and Oevermann, Michael and Meiselbach, Falko T. and Schmidt, Heiko and Kerstein, Alan R.}, title = {Numerical study of liquid breakup at the surface of turbulent liquid jets using One-Dimensional Turbulence}, series = {26th Annual Conference on Liquid Atomization and Spray Systems, ILASS, proceedings of the Conference, Bremen, Germany, 08.09.2014 - 10.09.2014}, booktitle = {26th Annual Conference on Liquid Atomization and Spray Systems, ILASS, proceedings of the Conference, Bremen, Germany, 08.09.2014 - 10.09.2014}, address = {Bremen}, isbn = {978-3-00-047070-7}, abstract = {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.}, language = {en} } @inproceedings{GlaweSchmidtKerstein, author = {Glawe, Christoph and Schmidt, Heiko and Kerstein, Alan R.}, title = {ODTLES: Mulitscale turbulence modeling and buoyant application}, series = {Book of abstracts, 7th European Postgraduate Fluid Dynamics Conference, Ilmenau, Germany, 14th - 17th, July 2014}, booktitle = {Book of abstracts, 7th European Postgraduate Fluid Dynamics Conference, Ilmenau, Germany, 14th - 17th, July 2014}, address = {Ilmenau}, pages = {S.46}, language = {en} } @misc{JozefikKersteinSchmidtetal., author = {Jozefik, Zoltan and Kerstein, Alan R. and Schmidt, Heiko and Lyra, Sgouria and Kolla, Hemanth and Chen, Jackie H.}, title = {One-dimensional turbulence modeling of a turbulent counterflow flame with comparison to DNS}, series = {Combustion and Flame}, volume = {162}, journal = {Combustion and Flame}, number = {8}, issn = {1556-2921}, pages = {2999 -- 3015}, language = {en} } @misc{SchmidtGlaweJozefiketal., author = {Schmidt, Heiko and Glawe, Christoph and Jozefik, Zoltan and Meiselbach, Falko T. and Kerstein, Alan R.}, title = {On the benefits of ODT-based stochastic turbulence modeling}, series = {Proceedings in applied mathematics and mechanics : PAMM}, volume = {14}, journal = {Proceedings in applied mathematics and mechanics : PAMM}, number = {1}, issn = {1617-7061}, pages = {655 -- 656}, abstract = {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.}, language = {en} } @incollection{JozefikKersteinSchmidt, author = {Jozefik, Zoltan and Kerstein, Alan R. and Schmidt, Heiko}, title = {Towards a compressible reactive multiscale approach based on One-Dimensional Turbulence}, series = {Active Flow and Combustion Control 2014}, booktitle = {Active Flow and Combustion Control 2014}, editor = {King, Rudibert}, publisher = {Springer}, address = {Switzerland}, isbn = {978-3-319-11967-0}, pages = {197 -- 211}, abstract = {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.}, language = {en} } @inproceedings{BlehOstendorfMertenetal., author = {Bleh, D. and Ostendorf, Ralf and Merten, A. and Grahmann, Jan and Schenk, Harald and Kunzer, M. and Schmidt, R. and Wagner, J.}, title = {Miniaturization of a fast tunable external cavity QCL with customized gratings and MOEMS components}, series = {International Quantum Cascade Lasers School \& Workshop (IQCLSW), Policoro, Italy}, booktitle = {International Quantum Cascade Lasers School \& Workshop (IQCLSW), Policoro, Italy}, pages = {1 -- 2}, language = {en} }