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.
Finite-volume models with implicit subgrid-scale parameterization for the differentially heated rotating annulus
S. Borchert, U. Achatz, S. Remmler, S. Hickel, U. Harlander, M. Vincze, K.D. Alexandrov, F. Rieper, T. Heppelmann, S.I. Dolaptchiev (2014)
Meteorologische Zeitschrift 23: 561-580. doi: 10.1127/metz/2014/0548
The differentially heated rotating annulus is a classical experiment for the investigation of baroclinic flows and can be regarded as a strongly simplified laboratory model of the atmosphere in mid-latitudes. Data of this experiment, measured at the BTU Cottbus-Senftenberg, are used to validate two numerical finite-volume models (INCA and cylFloit) which differ basically in their grid structure.
Evolution of length scales and statistics of Richtmyer-Meshkov instability from direct numerical simulations
V.K. Tritschler, M. Zubel, S. Hickel, N.A. Adams (2014)
Physical Review E 90: 063001. doi: 10.1103/PhysRevE.90.063001
In this study we present direct numerical simulation results of the Richtmyer-Meshkov instability (RMI) initiated by Ma = 1.05, Ma = 1.2, and Ma = 1.5 shock waves interacting with a perturbed planar interface between air and SF6. At the lowest shock Mach number the fluids slowly mix due to viscous diffusion, whereas at the highest shock Mach number the mixing zone becomes turbulent.
Cut-element based immersed boundary method for moving geometries in compressible liquid flows with cavitation
F. Örley, V. Pasquariello, S. Hickel, N.A. Adams (2015)
Journal of Computational Physics 283: 1-22. doi: 10.1016/j.jcp.2014.11.028
The conservative immersed interface method for representing complex immersed solid boundaries or phase interfaces on Cartesian grids is improved and extended to allow for the simulation of weakly compressible fluid flows through moving geometries. We demonstrate that an approximation of moving interfaces by a level-set field results in unphysical oscillations in the vicinity of sharp corners when dealing with weakly compressible fluids such as water. By introducing an exact reconstruction of the cut-cell properties directly based on a surface triangulation of the immersed boundary, we are able to recover the correct flow evolution free of numerical artifacts.
Subgrid-scale modeling for implicit Large Eddy Simulation of compressible flows and shock turbulence interaction
S. Hickel, C.P. Egerer, J. Larsson (2014)
Physics of Fluids 26: 106101. doi: 10.1063/1.4898641
LES of Temporally Evolving Turbulent Cavitating Shear Layers
C.P. Egerer, S. Hickel, S.J. Schmidt, N.A. Adams (2014)
High Performance Computing in Science and Engineering ’14: 367-378 doi: 10.1007/978-3-319-10810-0_25
We present LES results of temporally evolving cavitating shear layers. Cavitation is modeled by a homogeneous equilibrium mixture model whereas the effect of subgrid-scale turbulence is accounted for by the Adaptive Local Deconvolution Method (ALDM). We quantitatively compare LES results with experimental data available in the literature.
On the construction of a direct numerical simulation of a breaking inertia-gravity wave in the upper-mesosphere
M.D. Fruman, S. Remmler, U. Achatz, S. Hickel (2014)
Journal of Geophysical Research 119: 11613-11640. doi: 10.1002/2014JD022046
A systematic approach to the direct numerical simulation (DNS) of breaking upper mesospheric inertia-gravity waves of amplitude close to or above the threshold for static instability is presented. Normal mode or singular vector analysis applied in a frame of reference moving with the phase velocity of the wave (in which the wave is a steady solution) is used to determine the most likely scale and structure of the primary instability
Spectral eddy viscosity of stratified turbulence
S. Remmler, S. Hickel (2014)
Journal of Fluid Mechanics 755, R6. doi: 10.1017/jfm.2014.423
The spectral eddy viscosity (SEV) concept is a handy tool for the derivation of large-eddy simulation (LES) turbulence models and for the evaluation of their performance in predicting the spectral energy transfer. We compute this quantity by filtering and truncating fully resolved turbulence data from direct numerical simulations (DNS) of neutrally and stably stratified homogeneous turbulence. The results qualitatively confirm the plateau–cusp shape, which is often assumed to be universal, but show a strong dependence on the test filter size. Increasing stable stratification not only breaks the isotropy of the SEV but also modifies its basic shape, which poses a great challenge for implicit and explicit LES methods. We find indications that for stably stratified turbulence it is necessary to use different subgrid-scale (SGS) models for the horizontal and vertical velocity components. Our data disprove models that assume a constant positive effective turbulent Prandtl number.
On the Richtmyer-Meshkov instability evolving from a deterministic multimode planar interface
V.K. Tritschler, B. Olson, S. Lele, S. Hickel, X.Y. Hu, N.A. Adams (2014)
Journal of Fluid Mechanics 755, 429-462. doi: 10.1017/jfm.2014.436
We investigate the shock-induced turbulent mixing between a light and a heavy gas, where a Richtmyer–Meshkov instability (RMI) is initiated by a shock wave with Mach number Ma = 1.5. The prescribed initial conditions define a deterministic multimode interface perturbation between the gases, which can be imposed exactly for different simulation codes and resolutions to allow for quantitative comparison. Well-resolved large-eddy simulations are performed using two different and independently developed numerical methods with the objective of assessing turbulence structures, prediction uncertainties and convergence behaviour.
Large-eddy simulation of turbulent cavitating flow in a micro channel
C.P. Egerer, S. Hickel, S.J. Schmidt, N.A. Adams (2014)
Physics of Fluids 26, 085102. doi: 10.1063/1.4891325
Large-eddy simulations (LES) of cavitating flow of a Diesel-fuel-like fluid in a generic throttle geometry are presented. Two-phase regions are modeled by a parameter-free thermodynamic equilibrium mixture model, and compressibility of the liquid and the liquid-vapor mixture is taken into account. The Adaptive Local Deconvolution Method (ALDM), adapted for cavitating flows, is employed for discretizing the convective terms of the Navier-Stokes equations for the homogeneous mixture.
Large-eddy simulation of a pseudo-shock system in a Laval nozzle
J.F. Quaatz, M. Giglmaier, S. Hickel, N.A. Adams (2014)
International Journal of Heat and Fluid Flow 49: 108-115. doi: 10.1016/j.ijheatfluidflow.2014.05.006
Well-resolved Large-Eddy Simulations (LES) of a pseudo-shock system in the divergent part of a Laval nozzle with rectangular cross section are conducted and compared with experimental results. The LES matches the parameter set of a reference experiment. Details of the experiment, such as planar side walls, are taken into account, all wall boundary layers are well-resolved and no wall model is used.
Large-eddy simulation of passive shock-wave/boundary-layer interaction control
V. Pasquariello, M. Grilli, S. Hickel, N.A. Adams (2014)
International Journal of Heat and Fluid Flow 49: 116-127. doi: 10.1016/j.ijheatfluidflow.2014.04.005
We investigate a passive flow-control technique for the interaction of an oblique shock generated by an 8.8° wedge with a turbulent boundary-layer at a free-stream Mach number of Ma∞ = 2.3 and a Reynolds number based on the incoming boundary-layer thickness of Reδ = 60 500 by means of large-eddy simulation (LES).