On the application of WKB theory for the simulation of the weakly nonlinear dynamics of gravity waves
J. Muraschko, M.D. Fruman, U. Achatz, S. Hickel, Y. Toledo (2015)
Quarterly Journal of the Royal Meteorological Society 141: 676-697. doi: 10.1002/qj.2381
The dynamics of internal gravity waves is modelled using Wentzel–Kramer–Brillouin (WKB) theory in position–wave number phase space. A transport equation for the phase-space wave-action density is derived for describing one-dimensional wave fields in a background with height-dependent stratification and height- and time-dependent horizontal-mean horizontal wind, where the mean wind is coupled to the waves through the divergence of the mean vertical flux of horizontal momentum associated with the waves.
Quantification of initial-data uncertainty on a shock-accelerated gas cylinder
V.K. Tritschler, A. Avdonin, S. Hickel, X.Y. Hu, N.A. Adams (2014)
Physics of Fluids 26: 026101. doi: 10.1063/1.4865756
We quantify initial-data uncertainties on a shock accelerated heavy-gas cylinder by two-dimensional well-resolved direct numerical simulations. A high-resolution compressible multicomponent flow simulation model is coupled with a polynomial chaos expansion to propagate the initial-data uncertainties to the output quantities of interest.
Numerical modeling of separated flows at moderate Reynolds numbers appropriate for turbine blades and unmanned aero vehicles
G. Castiglioni, J.A. Domaradzki, V. Pasquariello, S. Hickel, M. Grilli (2014)
International Journal of Heat and Fluid Flow 49: 92-99. doi: 10.1016/j.ijheatfluidflow.2014.02.003
Flows over airfoils and blades in rotating machinery, for unmanned and micro-aerial vehicles, wind turbines, and propellers consist of a laminar boundary layer near the leading edge that is often followed by a laminar separation bubble and transition to turbulence further downstream. Typical RANS turbulence models are inadequate for such flows. Direct numerical simulation (DNS) is the most reliable, but is also the most computationally expensive alternative. This work assesses the capability of Immersed Boundary (IB) methods and Large Eddy Simulations (LES) to reduce the computational requirements for such flows and still provide high quality results.
On the Kolmogorov inertial subrange developing from Richtmyer-Meshkov instability
V.K. Tritschler, S. Hickel, X.Y. Hu, N.A. Adams (2013)
Physics of Fluids 25: 071701. doi: 10.1063/1.4813608
We present results of well-resolved direct numerical simulations (DNS) of the turbulent flowevolving from Richtmyer-Meshkov instability (RMI) in a shock-tube with square cross section. The RMI occurs at the interface between a mixture of O2 and N2 (light gas) and SF6 and acetone (heavy gas).
Numerical simulation of a Richtmyer-Meshkov instability with an adaptive central-upwind 6th-order WENO scheme
V.K. Tritschler, X.Y. Hu, S. Hickel, N.A. Adams (2013)
Physica Scripta 2013: 014016. doi: 10.1088/0031-8949/2013/T155/014016
Two-dimensional simulations of the single-mode Richtmyer–Meshkov instability (RMI) are conducted and compared to experimental results of Jacobs and Krivets (2005).
Direct numerical simulation of a breaking inertia-gravity wave
S. Remmler, M.D. Fruman, S. Hickel (2013)
Journal of Fluid Mechanics 722: 424-436. doi: 10.1017/jfm.2013.108
We have performed fully resolved three-dimensional numerical simulations of a statically unstable monochromatic inertia–gravity wave using the Boussinesq equations on an f - plane with constant stratification. The chosen parameters represent a gravity wave with almost vertical direction of propagation and a wavelength of 3 km breaking in the middle atmosphere.
Large-eddy simulation of supersonic turbulent boundary layer over a compression-expansion ramp
M. Grilli, S. Hickel, N.A. Adams (2013)
International Journal of Heat and Fluid Flow 42: 79-93. doi: 10.1016/j.ijheatfluidflow.2012.12.006
Results of a large-eddy simulation (LES) of a supersonic turbulent boundary layer flow along a compression–expansion ramp configuration are presented. The numerical simulation is directly compared with an available experiment at the same flow conditions. The compression–expansion ramp has a deflection angle of β = 25°, the free-stream Mach number is Ma∞ = 2.88, and the Reynolds number based on the incoming boundary layer thickness is Reδ = 132 840.
A conservative integration of the pseudo-incompressible equations with implicit turbulence parameterization
F. Rieper, S. Hickel, U. Achatz (2013)
Monthly Weather Review 141: 861-886. doi: 10.1175/MWR-D-12-00026.1
Durran’s pseudo-incompressible equations are integrated in a mass and momentum conserving way with a new implicit turbulence model. This system is soundproof, which has two major advantages over fully compressible systems: the Courant–Friedrichs–Lewy (CFL) condition for stable time advancement is no longer dictated by the speed of sound and all waves in the model are clearly gravity waves (GW).
Wall-modelled Implicit Large-Eddy Simulation of the RA16SC1 Highlift Configuration
M. Meyer, S. Hickel, C. Breitsamter, N.A. Adams (2013)
AIAA paper 2013-3037. doi: 10.2514/6.2013-3037
Industrially applied Computational Fluid Dynamics still faces a challenge when it comes to the accurate prediction of the complex flow over realistic highlift configurations. In this paper we demonstrate that the flow over the 3-element RA16SC1 highlift configuration can be efficiently and accurately predicted with Implicit Large-Eddy Simulation (ILES) on Cartesian adaptive grids.
An innovative approach to thermo-fluid-structure interaction based on an immersed interface method and a monolithic thermo-structure interaction algorithm
M. Grilli, S. Hickel, N.A. Adams, G. Hammerl, C. Danowski, W.A. Wall (2012)
AIAA paper 2012-3267. doi: 10.2514/6.2012-3267
We present a loosely-coupled approach for the solution of the thermo-fluid-structure interaction problem, based on Dirichlet-Neumann partitioning. A cartesian grid finite volume scheme, with conservative interface method is used for the fluid and a finite-element scheme for the thermo-structure problem. Special attention is given to the transfer of forces, temperatures and to the structural positions.
Experimental and numerical investigation on shockwave / turbulent boundary layer interaction
M. Grilli, L.S. Chen, S. Hickel, N.A. Adams, S. Willems, A. Gülhan (2012)
AIAA paper 2012-2701. doi: 10.2514/6.2012-2701
We report on an experimental and computational effort to study the interaction of a compressible turbulent boundary layer with an oblique shock wave. A wide range of shock intensities has been considered in the experiments through a variation of the free-stream Mach number.
Numerical modelling and investigation of symmetric and asymmetric cavitation bubble dynamics
E. Lauer, X.Y. Hu, S. Hickel, N.A. Adams (2012)
Computers and Fluids 69: 1-19. doi: 10.1016/j.compfluid.2012.07.020
In this paper, we investigate the high-speed dynamics of symmetric and asymmetric cavitation bubble-collapse. For this purpose, a sharp-interface numerical model is employed, that includes a numerically efficient evaporation/condensation model.
A parametrized non-equilibrium wall-model for large-eddy simulations
S. Hickel, E. Touber, J. Bodart, J. Larsson (2012)
Proceedings of the 2012 Summer Program, Center for Turbulence Research, Stanford University.
Wall-models are essential for enabling large-eddy simulations of realistic problems at high Reynolds numbers. The present study is focused on approaches that directly model the wall shear stress, specifically on filling the gap between models based on wall-normal ordinary differential equations (ODEs) that assume equilibrium and models based on full partial differential equations that do not. We develop ideas for how to incorporate non-equilibrium effects (most importantly, strong pressure-gradient effects) in the wall- model while still solving only wall-normal ODEs.
Direct and large-eddy simulation of stratified turbulence
S. Remmler, S. Hickel (2012)
International Journal of Heat and Fluid Flow 35: 13-24. doi: 10.1016/j.ijheatfluidflow.2012.03.009
Simulations of geophysical turbulent flows require a robust and accurate subgrid-scale turbulence modeling. To evaluate turbulence models for stably stratified flows, we performed direct numerical simulations (DNSs) of the transition of the three-dimensional Taylor–Green vortex and of homogeneous stratified turbulence with large-scale horizontal forcing.
Numerical investigation of collapsing cavity arrays
E. Lauer, X.Y. Hu, S. Hickel, N.A. Adams (2012)
Physics of Fluids 24: 052104. doi: 10.1063/1.4719142
Analysis of unsteady behavior in shockwave turbulent boundary layer interaction
M. Grilli, P.J. Schmidt, S. Hickel, N.A. Adams (2012)
Journal of Fluid Mechanics 700: 16-28. doi: 10.1017/jfm.2012.37
The unsteady behaviour in shockwave turbulent boundary layer interaction is investigated by analysing results from a large eddy simulation of a supersonic turbulent boundary layer over a compression–expansion ramp. The flow dynamics are analysed by a dynamic mode decomposition which shows the presence of a low-frequency mode associated with the pulsation of the separation bubble and accompanied by a forward–backward motion of the shock.