Reynolds number effects in shock-wave/turbulent boundary-layer interactions
L. Laguarda, S. Hickel, F.F.J. Schrijer, B.W. van Oudheusden (2024)
Journal of Fluid Mechanics (in press)
We investigate Reynolds number effects in strong shock-wave/turbulent-boundary layer interactions (STBLI) by leveraging a new database of wall-resolved and long-integrated large-eddy simulations (LES). The database encompasses STBLI with massive boundary-layer separation at Mach 2.0, impinging-shock angle 40° and friction Reynolds numbers Reτ = 355, Reτ = 1226, and Reτ = 5118.
Passive stabilization of crossflow instabilities by a reverse lift-up effect
J. Casacuberta, S. Hickel, M. Kotsonis (2024)
Physical Review Fluids 9: 043903. doi: 10.1103/PhysRevFluids.9.043903
A novel mechanism is identified, through which a spanwise-invariant surface feature (a two-dimensional forward-facing step) significantly stabilizes the stationary crossflow instability of a three-dimensional boundary layer. The mechanism is termed here as reverse lift-up effect, inasmuch as it acts reversely to the classic lift-up effect; that is, kinetic energy of an already-existing shear-flow instability is transferred to the underlying laminar flow through the action of cross-stream perturbations.
Assessment of immersed boundary methods for hypersonic flows with gas–surface interactions
A.O. Başkaya, M. Capriati, A. Turchi, T. Magin, S. Hickel (2024)
Computers & Fluids 270: 106134. doi: 10.1016/j.compfluid.2023.106134
The efficacy of immersed boundary (IB) methods with adaptive mesh refinement (AMR) techniques is assessed in the context of atmospheric entry applications, including effects of chemical nonequilibrium (CNE) and gas–surface interactions (GSI). We scrutinize a conservative cut-cell IB method and two non-conservative IB methods, comparing their results with analytical solutions, data from the literature, and results obtained with a reference solver that operates on body-fitted grids.
Shock-wave/turbulent boundary-layer interaction with a flexible panel
L. Laguarda, S. Hickel, F.F.J. Schrijer, B.W. van Oudheusden (2024)
Physics of Fluids 36: 016120. doi: 10.1063/5.0179082
The dynamic coupling between a Mach 2.0 shock-wave/turbulent boundary-layer interaction (STBLI) and a flexible panel is investigated. Wall-resolved large-eddy simulations are performed for a baseline interaction over a flat-rigid wall, a coupled interaction with a flexible panel, and a third interaction over a rigid surface that is shaped according to the mean panel deflection of the coupled case.
Assessment of Reynolds number effects in supersonic turbulent boundary layers
L. Laguarda, S. Hickel, F.F.J. Schrijer, B.W. van Oudheusden (2024)
International Journal of Heat and Fluid Flow 105: 109234. doi: 10.1016/j.ijheatfluidflow.2023.109234
Wall-resolved large-eddy simulations (LES) are performed to investigate Reynolds number effects in supersonic turbulent boundary layers (TBLs) at Mach 2.0. The resulting database covers more than a decade of friction Reynolds number Reτ from 242 to 5554, which considerably extends the parameter range of current high-fidelity numerical studies. Reynolds number trends are identified on a variety of statistics for skin-friction, velocity and thermodynamic variables. The efficacy of recent scaling laws as well as compressibility effects are also assessed.
Analysis of improved digital filter inflow generation methods for compressible turbulent boundary layers
L. Laguarda, S. Hickel (2024)
Computers & Fluids 268: 106105. doi: 10.1016/j.compfluid.2023.106105
We propose several enhancements to improve the accuracy and performance of the digital filter turbulent inflow generation technique and assess their efficacy in the context of wall-resolved large-eddy simulations of a compressible turbulent boundary layer.
Convective instabilities in a laminar shock-wave/boundary-layer interaction
S.E.M. Niessen, K.J. Groot, S. Hickel, V.E. Terrapon (2023)
Physics of Fluids 35: 024101. doi: 10.1063/5.0135590
Linear stability analyses are performed to study the dynamics of linear convective instability mechanisms in a laminar shock-wave/boundary-layer interaction at Mach 1.7. In order to account for all two-dimensional gradients elliptically, we introduce perturbations into an initial-value problem that are found as solutions to an eigenvalue problem formulated in a moving frame of reference.
GPU-accelerated simulations for eVTOL aerodynamic analysis
V. Pasquariello, Y. Bunk, S. Eberhardt, P.-H. Huang, J. Matheis, M. Ugolotti, S. Hickel (2023)
AIAA Scitech paper 2023-2107. doi: 10.2514/6.2023-2107
The demand for fast, high-fidelity, scale-resolving computational fluid dynamics (CFD) simulations is continuously growing. Especially new emerging aviation technologies, such as electrical vertical take-off and landing aircraft (eVTOL), strongly rely on advanced numerical methods to retain development life-cycle costs and achieving design targets more quickly. This paper presents a cutting-edge large-eddy simulations (LES) solver developed to enable over-night turnaround times for full aircraft simulations on advanced graphics processing unit (GPU) architectures.
Experimental and numerical investigation into the drag performance of dimpled surfaces in a turbulent boundary layer
O.W.G. van Campenhout, M. van Nesselrooij, Y.Y. Lin, B.W. van Oudheusden, S. Hickel (2023)
International Journal of Heat and Fluid Flow 100: 109110. doi: 10.1016/j.ijheatfluidflow.2023.109110
Although several previous studies have reported a potential drag-reducing effect of dimpled surfaces in turbulent boundary layers, there is a lack of replicability across experiments performed by different research groups. To contribute to the dialogue, we scrutinize one of the most studied dimple geometries reported in the literature, which has a dimple diameter of 20 mm and a depth of 0.5 mm.
An enhanced algorithm for online Proper Orthogonal Decomposition and its parallelization for unsteady simulations
X. Li, S. Hulshoff, S. Hickel (2022)
Computers & Mathematics with Applications 126: 43-59. doi: 10.1016/j.camwa.2022.09.007
We present an enhanced online algorithm based on incremental Singular Value Decomposition (SVD), which can be used to efficiently perform a Proper Orthogonal Decomposition (POD) analysis on the fly. The proposed enhanced algorithm for modal analysis has significantly better computational efficiency than the standard incremental SVD and good parallel scalability, such that the strong reduction of computational cost is maintained in parallel computations.
Unsteady mechanisms in shock wave and boundary layer interactions over a forward-facing step
W. Hu, S. Hickel, B.W. van Oudheusden (2022)
Journal of Fluid Mechanics 949: A2. doi: 10.1017/jfm.2022.737
The flow over a forward-facing step (FFS) at Ma∞=1.7 and Re𝛿 = 13 718 is investigated by well-resolved large-eddy simulation. To investigate effects of upstream flow structures and turbulence on the low-frequency dynamics of the shock wave/boundary layer interaction (SWBLI), two cases are considered: one with a laminar inflow and one with a turbulent inflow.
Large eddy simulations of reacting and non-reacting transcritical fuel sprays using multiphase thermodynamics
M. Fathi, S. Hickel, D. Roekaerts (2022)
Physics of Fluids 34: 085131. doi: 10.1063/5.0099154
We present a novel framework for high-fidelity simulations of inert and reacting sprays with highly accurate and computationally efficient models for complex real-gas effects in high-pressure environments, especially for the hybrid subcritical/supercritical mode of evaporation during the mixing of fuel and oxidizer at transcritical conditions.
Direct numerical simulation of interaction between a stationary crossflow instability and forward-facing steps
J. Casacuberta, S. Hickel, S. Westerbeek, M. Kotsonis (2022)
Journal of Fluid Mechanics 943: A46. doi: 10.1017/jfm.2022.456
The interaction between forward-facing steps of several heights and a pre-existing critical stationary crossflow instability of a swept-wing boundary layer is analysed.
Verification and Validation of Immersed Boundary Solvers for Hypersonic Flows with Gas-Surface Interaction
A.O. Başkaya, M. Capriati, D. Ninni, F. Bonelli, G. Pascazio, A. Turchi, T. Magin, S. Hickel (2022)
AIAA Aviation Forum, Chicago. AIAA paper 2022-3276. doi: 10.2514/6.2022-3276
Verification and validation results of two immersed boundary solvers, INCA and CHESS, for atmospheric entry flows characterized by complex fluid thermochemistry and gas-surface interactions (GSI) are presented. Results are compared with those obtained with the body-conforming solver US3D, which is coupled to the same external thermochemistry library, Mutation++, as INCA and CHESS. In these campaigns, the INCA solver has shown an almost perfect agreement with the body-conforming reference solver and other reference results from literature.
Secondary instabilities in swept-wing boundary layers: Direct Numerical Simulations and BiGlobal stability analysis
J. Casacuberta, K.J. Groot, S. Hickel, M. Kotsonis (2022)
SciTech Forum and Exposition, San Diego. AIAA paper 2022-2330, doi: 10.2514/6.2022-2330
The evolution of secondary instabilities in a three-dimensional stationary-crossflow-dominated boundary layer is investigated by means of Direct Numerical Simulations (DNS) and linear spanwise BiGlobal stability analysis. Single-frequency unsteady disturbances and a critical stationary crossflow mode are considered.
Experimental investigation of shock–shock interactions with variable inflow Mach number
L. Laguarda, J. Santiago Patterson, F.F.J. Schrijer, B.W. van Oudheusden, S. Hickel (2021)
Shock Waves 3: 457-468. doi: 10.1007/s00193-021-01029-3
Experiments on shock–shock interactions were conducted in a transonic–supersonic wind tunnel with variable free-stream Mach number functionality. Transition between the regular interaction (RI) and the Mach interaction (MI) was induced by variation of the free-steam Mach number for a fixed interaction geometry, as opposed to most previous studies where the shock generator angles are varied at constant Mach number.