A priori tests of subgrid-scale models in an anisothermal turbulent channel flow at low mach number

TL;DR

This paper evaluates subgrid-scale models for low Mach number anisothermal turbulent channel flows using direct numerical simulations, comparing existing models and proposing new ones, with a focus on near-wall behavior and model accuracy.

Contribution

The study introduces two new subgrid-scale models tailored for anisothermal low Mach number flows and assesses their performance against existing models using a priori tests.

Findings

AMD and scalar AMD models outperform others in accuracy

No significant difference between classical and Favre filters in model performance

Models capture energetic contributions but not flow effects accurately

Abstract

The subgrid-scale modelling of a low Mach number strongly anisothermal turbulent flow is investigated using direct numerical simulations. The study is based on the filtering of the low Mach number equations, suited to low Mach number flows with highly variable fluid properties. The results are relevant to formulations of the filtered low Mach number equations established with the classical filter or the Favre filter. The two most significant subgrid terms of the filtered low Mach number equations are considered. They are associated with the momentum convection and the density-velocity correlation. We focus on eddy-viscosity and eddy-diffusivity models. Subgrid-scale models from the literature are analysed and two new models are proposed. The subgrid-scale models are compared to the exact subgrid term using the instantaneous flow field of the direct numerical simulation of a strongly anisothermal fully developed turbulent channel flow. There is no significant differences between the use of the classical and Favre filter regarding the performance of the models. We suggest that the models should take into account the asymptotic near-wall behaviour of the filter length. Eddy-viscosity and eddy-diffusivity models are able to represent the energetic contribution of the subgrid term but not its effect in the flow governing equations. The AMD and scalar AMD models are found to be in better agreement with the exact subgrid terms than the other investigated models in the a priori tests.