Adaptive reduced-order modeling for non-linear fluid-structure interaction
A. Thari, V. Pasquariello, N. Aage, S. Hickel (2021)
Computers and Fluids 229: 105099. doi: 10.1016/j.compfluid.2021.105099
We present an adaptive reduced-order model for the efficient time-resolved simulation of fluid–structure interaction problems with complex and non-linear deformations. The model is based on repeated linearizations of the structural balance equations. Upon each linearization step, the number of unknowns is strongly decreased by using modal reduction, which leads to a substantial gain in computational efficiency.
Towards adjoint-based mesh refinement for Large Eddy Simulation using reduced-order primal solutions: Preliminary 1D Burgers study
X. Li, S. Hulshoff, S. Hickel (2021)
Computer Methods in Applied Mechanics and Engineering 379: 113733. doi: 10.1016/j.cma.2021.113733
Adaptive Mesh Refinement (AMR) is potentially an effective way to automatically generate computational meshes for high-fidelity simulations such as Large Eddy Simulation (LES). When combined with adjoint methods, which are able to localize error contributions, AMR can generate meshes that are optimal for computing a physical quantity of interest (e.g. lift or drag).
Customized data-driven RANS closures for bi-fidelity LES–RANS optimization
Y. Zhang, R.P. Dwight, M. Schmelzer, J.F. Gómez, Z.-H. Han, S. Hickel (2021)
Journal of Computational Physics 432: 110153. doi: 10.1016/j.jcp.2021.110153
Multi-fidelity optimization methods promise a high-fidelity optimum at a cost only slightly greater than a low-fidelity optimization. This promise is seldom achieved in practice, due to the requirement that low- and high-fidelity models correlate well. In this article, we propose an efficient bi-fidelity shape optimization method for turbulent fluid-flow applications with Large-Eddy Simulation (LES) and Reynolds-averaged Navier-Stokes (RANS) as the high- and low-fidelity models within a hierarchical-Kriging surrogate modelling framework.
Mechanisms of interaction between stationary crossflow instabilities and forward-facing steps
J. Casacuberta, S. Hickel, M. Kotsonis (2021)
AIAA Scitech paper 2021-0854. doi: 10.2514/6.2021-0854
We study the interaction between a stationary crossflow instability and forward-facing steps in a swept-wing boundary layer using Direct Numerical Simulations (DNS). The station- ary primary crossflow mode is imposed at the inflow. Steps of several heights are modeled.
Low-frequency unsteadiness mechanisms in shock wave/turbulent boundary layer interactions over a backward-facing step
W. Hu, S. Hickel, B.W. van Oudheusden (2021)
Journal of Fluid Mechanics 915: A107. doi: 10.1017/jfm.2021.95
The low-frequency unsteady motions behind a backward-facing step (BFS) in a turbulent flow at Ma=1.7 and Re∞=1.3718×107 m−1 are investigated using a well-resolved large-eddy simulation.
Rapid multi-component phase-split calculations using volume functions and reduction methods
M. Fathi, S. Hickel (2021)
AIChE Journal 67: e17174. doi: 10.1002/aic.17174
We present a new family of fast and robust methods for the calculation of the vapor–liquid equilibrium at isobaric-isothermal (PT-flash), isochoric-isothermal (VT-flash), isenthalpic-isobaric (HP-flash), and isoenergetic-isochoric (UV-flash) conditions. The framework is provided by formulating phase-equilibrium conditions for multi-component mixtures in an effectively reduced space based on the molar specific value of the recently introduced volume function derived from the Helmholtz free energy.
Assessment of RANS Turbulence Models for Straight Cooling Ducts: Secondary Flow and Strong Property Variation Effects
T. Kaller, A. Doehring, S. Hickel, S.J. Schmidt, N.A. Adams (2021)
Notes on Numerical Fluid Mechanics and Multidisciplinary Design 146: 309-321. doi: 10.1007/978-3-030-53847-7_20
We present well-resolved RANS simulations of two generic asymmetrically heated cooling channel configurations, a high aspect ratio cooling duct operated with liquid water at Reb=110 000 and a cryogenic transcritical channel operated with methane at Reb=16 000.
Inertia gravity waves breaking in the middle atmosphere: energy transfer and dissipation tensor anisotropy
T. Pestana, M. Thalhammer, S. Hickel (2020)
Journal of the Atmospheric Sciences 77: 3193-3210. doi: 10.1175/JAS-D-19-0342.1
We present direct numerical simulations of inertia–gravity waves breaking in the middle–upper mesosphere. We consider two different altitudes, which correspond to the Reynolds number of 28 647 and 114 591 based on wavelength and buoyancy period. While the former was studied by Remmler et al., it is here repeated at a higher resolution and serves as a baseline for comparison with the high-Reynolds-number case.
Influence of upstream disturbances on the primary and secondary instabilities in a supersonic separated flow over a backward-facing step
W. Hu, S. Hickel, B.W. van Oudheusden (2020)
Phys. Fluids 32: 056102. doi: 10.1063/5.0005431
Dynamics of unsteady asymmetric shock interactions
L. Laguarda, S. Hickel, F.F.J. Schrijer, B.W. van Oudheusden (2020)
Journal of Fluid Mechanics 888: A18. doi: 10.1017/jfm.2020.28
The response of asymmetric and planar shock interactions to a continuous excitation of the lower incident shock is investigated numerically. Incident shock waves and centred expansion fans are generated by two wedges asymmetrically deflecting the inviscid free stream flow at Mach 3.
Prediction capability of RANS turbulence models for asymmetrically heated high-aspect-ratio duct flows
T. Kaller, S. Hickel, N.A. Adams (2020)
AIAA Scitech paper 2020-0354. doi: 10.2514/6.2020-0354
We present well-resolved RANS simulations of a high-aspect-ratio generic cooling duct configuration consisting of an adiabatic straight feed line followed by a heated straight section ending with a 90° bend. The configuration is asymmetrically heated with a temperature difference of ∆T = 40 K. As fluid liquid water is used at a bulk Reynolds number of Reb = 110 000.
Transitional Flow Dynamics Behind a Micro-Ramp
J. Casacuberta, K.J. Groot, Q. Ye, S. Hickel (2020)
Flow Turbulence and Combustion 104: 533-552. doi: 10.1007/s10494-019-00085-1
Micro-ramps are popular passive flow control devices which can delay flow separation by re-energising the lower portion of the boundary layer. We compute the laminar base flow, the instantaneous transitional flow, and the mean flow around a micro-ramp immersed in a quasi-incompressible boundary layer at supercritical roughness Reynolds number.
Rossby-number effects on columnar eddy formation and the energy dissipation law in homogeneous rotating turbulence
T. Pestana, S. Hickel (2020)
Journal of Fluid Mechanics 885: A7. doi: 10.1017/jfm.2019.976
Two aspects of homogeneous rotating turbulence are quantified through forced direct numerical simulations in an elongated domain, which, in the direction of rotation, is approximately 340 times larger than the typical initial eddy size. First, by following the time evolution of the integral length scale along the axis of rotation ℓ‖, the growth rate of the columnar eddies and its dependence on the Rossby number 𝑅𝑜𝜀 is determined as 𝛾=3.90exp(−16.72𝑅𝑜𝜀) for 0.06⩽𝑅𝑜𝜀⩽0.31, where 𝛾 is the non-dimensional growth rate. Second, a scaling law for the energy dissipation rate 𝜀𝜈 is sought.
Dynamics of a supersonic transitional flow over a backward-facing step
W. Hu, S. Hickel, B.W. van Oudheusden (2019)
Phys. Rev. Fluids 4, 103904. doi: 10.1103/PhysRevFluids.4.103904
The transition mechanism and unsteady behavior behind a backward-facing step (BFS) in the supersonic regime at Ma = 1.7 and Reδ = 13718 is investigated using large-eddy simulation (LES). The visualization of the flow field shows that the transition process behind the step is initiated by a Kelvin-Helmholtz (K-H) instability of the separated shear layer, followed by secondary modal instabilities of the K-H vortices, leading to lambda-shaped vortices, hair-pin vortices and finally to a fully turbulent state.
A priori investigations into the construction and the performance of an explicit algebraic subgrid-scale stress model
A.K. Gnanasundaram, T. Pestana, S. Hickel (2019)
11th International Symposium on Turbulence and Shear Flow Phenomena. TSFP paper 2019-286
We investigate the underlying assumptions of Explicit Algebraic Subgrid-Scale Models (EASSMs) for Large- Eddy Simulations (LESs) through an a priori analysis using data from Direct Numerical Simulations (DNSs) of homogeneous isotropic and homogeneous rotating turbulence. We focus on the performance of three models: the dynamic Smagorinsky (DSM) and the standard and dynamic explicit algebraic models as in Marstorp et al. (2009), here refereed to as SEA and DEA.
A one equation explicit algebraic subgrid-scale stress model
S. Hickel, A.K. Gnanasundaram, T. Pestana (2019)
11th International Symposium on Turbulence and Shear Flow Phenomena. TSFP paper 2019-275
Nonlinear Explicit Algebraic Subgrid-scale Stress Models (EASSMs) have shown high potential for Large Eddy Simulation (LES) of challenging turbulent flows on coarse meshes. A simplifying assumption made to enable the purely algebraic nature of the model is that the Subgrid-Scale (SGS) kinetic energy production and dissipation are in balance, i.e., P/ε = 1. In this work, we propose an improved EASSM design that does not involve this pre-calibration and retains the ratio P~ε as a space and time dependent variable.