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 ??? is determined as ?=3.90exp(−16.72???) for 0.06⩽???⩽0.31, where ? is the non-dimensional growth rate. Second, a scaling law for the energy dissipation rate ?? 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.
Regime transition in the energy cascade of rotating turbulence
T. Pestana, S. Hickel (2019)
Phys. Rev. E 99, 053103. doi: 10.1103/PhysRevE.99.053103
Transition from a split to a forward kinetic energy cascade system is explored in the context of rotating turbulence using direct numerical simulations with a three-dimensional isotropic random force uncorrelated with the velocity field. Our parametric study covers confinement effects in high-aspect-ratio domains and a broad range of rotation rates.
Effectivity and efficiency of selective frequency damping for the computation of unstable steady-state solutions
J. Casacuberta, K.J. Groot, H.J. Tol, S. Hickel (2018)
Journal of Computational Physics 375: 481-497. doi: 10.1016/j.jcp.2018.08.056
Selective Frequency Damping (SFD) is a popular method for the computation of globally unstable steady-state solutions in fluid dynamics. The approach has two model parameters whose selection is generally unclear. In this article, a detailed analysis of the influence of these parameters is presented, answering several open questions with regard to the effectiveness, optimum efficiency and limitations of the method.
Turbulent flow through a high aspect ratio cooling duct with asymmetric wall heating
Kaller, T., Pasquariello, V., Hickel, S., Adams, N.A. (2019)
Journal of Fluid Mechanics 860: 258-299. doi: 10.1017/jfm.2018.836
We present well-resolved large-eddy simulations of turbulent flow through a straight, high aspect ratio cooling duct operated with water at a bulk Reynolds number of Reb = 110 000 and an average Nusselt number of Nu = 371. The geometry and boundary conditions follow an experimental reference case and good agreement with the experimental results is achieved.
Multi-component vapor-liquid equilibrium model for LES of high-pressure fuel injection and application to ECN Spray A
J. Matheis, S. Hickel (2018)
International Journal of Multiphase Flow 99: 294-311. doi: 10.1016/j.ijmultiphaseflow.2017.11.001
We present and evaluate a two-phase model for Eulerian large-eddy simulations (LES) of liquid-fuel injection and mixing at high pressure. The model is based on cubic equations of state and vapor-liquid equilibrium calculations and can represent the coexistence of supercritical states and multi-component subcritical two-phase states via a homogeneous mixture approach.
Unsteady effects of strong shock-wave/boundary-layer interaction at high Reynolds number
V. Pasquariello, S. Hickel, N.A. Adams (2017)
Journal of Fluid Mechanics 828: 617-657. doi: 10.1017/jfm.2017.308
We analyse the low-frequency dynamics of a high Reynolds number impinging shock-wave/turbulent boundary-layer interaction (SWBLI) with strong mean-flow separation. The flow configuration for our grid-converged large-eddy simulations (LES) reproduces recent experiments for the interaction of a Mach 3 turbulent boundary layer with an impinging shock that nominally deflects the incoming flow by 19.6° . The Reynolds number based on the incoming boundary-layer thickness of Reδ ≈ 203 000 is considerably higher than in previous LES studies.