Direct numerical simulations of homogeneous isotropic turbulence in a dense gas

Abstract

Abstract. A study of turbulence in BZT dense gas flows is performed using DNS. It is shown that for a large but realistic intensity, the turbulence in dense gas flows behaves in a highly compressible manner when the average thermodynamic state lies within the inversion region in which the gas fundamental derivative is negative. A close similarity is observed in the evolution of the kinetic energy when the initial turbulent Mach number and the Taylor Reynolds number are matched regardless of the Equation of State (EoS) considered. A large turbulent Mach number is yet more easily attained in dense gas flows lying in the inversion region because of the low speed of sound associated with it. In this case the turbulence shows a highly compressible evolution with periodic exchanges between the internal and kinetic energies. In order to assess the capabilities of currently available Large Eddy Simulation (LES) subgrid-scale models, aposteriori tests are performed using the dynamic Smagorinsky model. Coherently with the hypothesis it relies on, the model perfectly captures the evolution of the kinetic energy when the turbulent Mach number is low enough. When using the perfect gas EoS at a higher turbulent Mach number the agreement is reasonable. Yet, when the average thermodynamic state lies within the inversion region and when using the thermal and caloric Martin&Hou EoS, the model is not able to capture the correct evolution of the kinetic energy. The results presented in this study call for a specific research effort directed towards the assessment and possibly the development of advanced subgrid-scale models for LES of turbulent dense gas flows.

Direct numerical simulations of temporal compressible mixing layers in a Bethe–Zel'dovich–Thompson dense gas: influence of the convective Mach number

“…So far, few DNS of DG flows have been achieved. DNS of decaying homogeneous isotropic turbulence (HIT) performed by Giauque, Corre & Menghetti (2017) shows that the dynamic Smagorinsky sub-grid-scale model is not able to correctly capture the temporal decay of the turbulent kinetic energy. They extended their analysis by performing a forced HIT highlighting significant differences in the sub-grid scale baropycnal work and the resolved pressure dilatation, which is reduced by a factor of 2 in a DG when compared with a perfect gas (PG) (Giauque, Corre & Vadrot 2020).…”

Analysis of turbulence characteristics in a temporal dense gas compressible mixing layer using direct numerical simulation

“…At the present time, few authors have achieved DNS of DG flows. Giauque, Corre & Menghetti (2017) have performed a DNS of decaying homogeneous isotropic turbulence (HIT) and concluded that the standard Smagorinski subgrid-scale (SGS) model does not capture correctly the temporal evolution of the turbulent kinetic energy (TKE) by comparing the LES prediction with the DNS reference results. The DNS also evidenced localized flow regions with strongly positive values for the velocity divergence that could correspond to expansion shock waves.…”