Three-dimensional reacting shock-bubble interaction
F. Diegelmann, S. Hickel, N.A. Adams (2017)
Combustion and Flame 181: 1339-1351. doi: 10.1016/j.combustflame.2017.03.026
We investigate a reacting shock–bubble interaction through three-dimensional numerical simulations with detailed chemistry. The convex shape of the bubble focuses the shock and generates regions of high pressure and temperature, which are sufficient to ignite the diluted stoichiometric H2-O2 gas mixture inside the bubble. We study the interaction between hydrodynamic instabilities and shock-induced reaction waves at a shock Mach number of Ma = 2.83.
Large-eddy simulation of turbulent, cavitating flow inside a 9-hole Diesel injector including needle movement
F. Örley, S. Hickel, S.J. Schmidt, N.A. Adams (2017)
International Journal of Engine Research 18:195-211. doi: 10.1177/1468087416643901
We investigate the turbulent multiphase flow inside a nine-hole common rail Diesel injector during a full injection cycle of ISO 4113 diesel fuel into air by implicit large-eddy simulation (LES). The simulation includes a prescribed needle movement obtained from a one-dimensional multi-domain simulation.
Multi-component vapor-liquid equilibrium model for LES and application to ECN Spray A
J. Matheis, S. Hickel (2016)
Proceedings of the 2016 Summer Program, Center for Turbulence Research, Stanford University. (also available online on arXiv:1609.08533)
We present and evaluate a detailed multi-species two-phase thermodynamic equilibrium model for large-eddy simulations (LES) of liquid-fuel injection and mixing at high pressure. The model can represent the coexistence of supercritical states and multi-component subcritical two-phase states.
Large-eddy simulation of nitrogen injection at trans- and supercritical conditions
H. Müller, C. Niedermeier, J. Matheis, M. Pfitzner, S. Hickel (2016)
Physics of Fluids 28: 015102. doi: 10.1063/1.4937948
Large-eddy simulations (LES) of cryogenic nitrogen injection into a warm environment at supercritical pressure are performed and real-gas thermodynamics models and subgrid-scale (SGS) turbulence models are evaluated. The comparison of different SGS models — the Smagorinsky model, the Vreman model, and the adaptive local deconvolution method — shows that the representation of turbulence on the resolved scales has a notable effect on the location of jet break-up, whereas the particular modeling of unresolved scales is less important for the overall mean flow field evolution. More important are the models for the fluid’s thermodynamic state.
Shock Mach number influence on reaction wave types and mixing in reactive shock-bubble interaction
F. Diegelmann, S. Hickel, N.A. Adams (2016)
Combustion and Flame 174: 85-99. doi: 10.1016/j.combustflame.2016.09.014
We present numerical simulations for a reactive shock–bubble interaction with detailed chemistry. The convex shape of the bubble leads to shock focusing, which generates spots of high pressure and temperature. Pressure and temperature levels are sufficient to ignite the stoichiometric H2–O2 gas mixture. Shock Mach numbers between Ma = 2.13 and Ma = 2.90 induce different reaction wave types (deflagration and detonation).
On the pressure dependence of ignition and mixing in two-dimensional reactive shock-bubble interaction
F. Diegelmann, V. Tritschler, S. Hickel, N.A. Adams (2016)
Combustion and Flame 163:414-426. doi: 10.1016/j.combustflame.2015.10.016
We analyse results of numerical simulations of reactive shock-bubble interaction with detailed chemistry. The interaction of the Richtmyer–Meshkov instability and shock-induced ignition of a stoichiometric H2-O2 gas mixture is investigated. Different types of ignition (deflagration and detonation) are observed at the same shock Mach number of Ma = 2.30 upon varying initial pressure.
Efficient implicit LES method for the simulation of turbulent cavitating flows
C.P. Egerer, S.J. Schmidt, S. Hickel, N.A. Adams (2016)
Journal of Computational Physics 316: 453-469. doi: 10.1017/10.1016/j.jcp.2016.04.021
We present a numerical method for efficient large-eddy simulation of compressible liquid flows with cavitation based on an implicit subgrid-scale model. Phase change and subgrid-scale interface structures are modeled by a homogeneous mixture model that assumes local thermodynamic equilibrium. Unlike previous approaches, emphasis is placed on operating on a small stencil (at most four cells).
A cut-cell finite volume-finite element coupling approach for fluid-structure interaction in compressible flow
V. Pasquariello, G. Hammerl, F. Örley, S. Hickel, C. Danowski, A. Popp, W.A. Wall, N.A. Adams (2016)
Journal of Computational Physics 307: 670-695. doi: 10.1016/j.jcp.2015.12.013
We present a loosely coupled approach for the solution of fluid–structure interaction problems between a compressible flow and a deformable structure. The method is based on staggered Dirichlet–Neumann partitioning. The interface motion in the Eulerian frame is accounted for by a conservative cut-cell Immersed Boundary method. The present approach enables sub-cell resolution by considering individual cut-elements within a single fluid cell, which guarantees an accurate representation of the time-varying solid interface.
Volume translation methods for real-gas computational fluid dynamics simulations
J. Matheis, H. Müller, C. Lenz, M. Pfitzner, S. Hickel (2016)
Journal of Supercritical Fluids 107: 422-432.
doi: 10.1016/j.supflu.2015.10.004
We report on recent developments within the field of real gas thermodynamics models with particular emphasis on volume translation methods for cubic equations of state. On the basis of the generalized form of a cubic equation of state, a mathematical framework for applying volume translations is provided, allowing for an unified and thermodynamically consistent formulation in the context of computational fluid dynamics simulations.
Large-eddy simulation of coaxial LN2/GH2 injection at trans- and supercritical conditions
H. Müller, M. Pfitzner, J. Matheis, S. Hickel (2015)
Journal of Propulsion and Power 32: 46-56. doi: 10.2514/1.B35827
Large-eddy simulations are carried out for the coaxial injection of liquid nitrogen and preheated hydrogen at supercritical pressures. A novel volume-translation method on the basis of the cubic Peng–Robinson equation of state is introduced for the use in multispecies large-eddy simulations and is tested for both trans- and supercritical injection conditions.
Validation of large-eddy simulation methods for gravity wave breaking
S. Remmler, S. Hickel, M.D. Fruman, U. Achatz (2015)
Journal of the Atmospheric Sciences 72: 3537-3562. doi: 10.1175/JAS-D-14-0321.1
To reduce the computational costs of numerical studies of gravity wave breaking in the atmosphere, the grid resolution has to be reduced as much as possible. Insufficient resolution of small-scale turbulence demands a proper turbulence parameterization in the framework of a large-eddy simulation (LES). We consider three different LES methods—the adaptive local deconvolution method (ALDM), the dynamic Smagorinsky method (DSM), and a naïve central discretization without turbulence parameterization (CDS4)—for three different cases of the breaking of well-defined monochromatic gravity waves.
Large-eddy simulation of cavitating nozzle flow and primary jet break-up
F. Örley, T. Trummler, S. Hickel, M.S. Mihatsch, S.J. Schmidt, N.A. Adams (2015)
Physics of Fluids 27: 086101. doi: 10.1063/1.4928701
We employ a barotropic two-phase/two-fluid model to study the primary break-up of cavitating liquid jets emanating from a rectangular nozzle, which resembles a high aspect-ratio slot flow. All components (i.e., gas, liquid, and vapor) are represented by a homogeneous mixture approach. The cavitating fluid model is based on a thermodynamic-equilibrium assumption. Compressibility of all phases enables full resolution of collapse-induced pressure wave dynamics.
On the transition between regular and irregular shock patterns of shock-wave/boundary-layer interactions
J. Matheis, S. Hickel (2015)
Journal of Fluid Mechanics 776: 200-234. doi: 10.1017/jfm.2015.319
The reflection of strong oblique shock waves at turbulent boundary layers is studied numerically and analytically. A particular emphasis is put on the transition between regular shock-wave/boundary-layer interaction (SWBLI) and Mach reflection (irregular SWBLI). The classical two- and three-shock theory and a generalised form of the free interaction theory are used for the analysis of well-resolved large-eddy simulations (LES) and for the derivation of stability criteria.
Assessing the numerical dissipation rate and viscosity in numerical simulations of fluid flows
F. Schranner, J.A. Domaradzki, S. Hickel, N.A. Adams (2015)
Computers and Fluids 114: 84-97. doi:10.1016/j.compfluid.2015.02.011
We propose a method for quantifying the effective numerical dissipation rate and effective numerical viscosity in Computational Fluid Dynamics (CFD) simulations. Different from previous approaches that were formulated in spectral space, the proposed method is developed in a physical-space representation and allows for determining numerical dissipation rates and viscosities locally, that is, at the individual cell level, or for arbitrary subdomains of the computational domain.
Benchmarking in a rotating annulus: A comparative experimental and numerical study of baroclinic wave dynamics
M. Vincze, S. Borchert, U. Achatz, T. von Larcher, M. Baumann, C. Liersch, S. Remmler, T. Beck, K.D. Alexandrov, C. Egbers, J. Fröhlich, V. Heuveline, S. Hickel, U. Harlander (2015)
Meteorologische Zeitschrift 23: 611-635. doi: 10.1127/metz/2014/0600
The differentially heated rotating annulus is a widely studied tabletop-size laboratory model of the general mid-latitude atmospheric circulation. The two most relevant factors of cyclogenesis, namely rotation and meridional temperature gradient are quite well captured in this simple arrangement. The radial temperature difference in the cylindrical tank and its rotation rate can be set so that the isothermal surfaces in the bulk tilt, leading to the formation of baroclinic waves.
Wall modeled large-eddy simulation of the VFE-2 delta wing
C. Zwerger, S. Hickel, C. Breitsamter, N.A. Adams (2015)
AIAA paper 2015-2572. doi: 10.2514/6.2015-2572
We performed wall-modeled large-eddy simulation of the flow field around the VFE-2 delta wing, focusing on two aspects: (1) leading-edge bluntness effects on the primary vortex separation and (2) vortex breakdown above the wing and its control. Regarding aspect (1), the VFE-2 delta wing with sharp leading-edge (SLE) and medium radius round leading-edge (MRLE) are considered for three angles of attack α = {13°, 18°, 23°} leading to different overall flow characteristics.