Wall-modeled large-eddy simulation of turbulent smooth body separation using the OpenFOAM flow solver

TL;DR

This study evaluates the capabilities of OpenFOAM's wall-modeled large-eddy simulation (WMLES) for turbulent flow separation, highlighting the importance of numerics and wall models in prediction accuracy.

Contribution

It systematically assesses different wall models and numerical schemes in OpenFOAM for flow separation, identifying key factors affecting simulation performance.

Findings

Non-equilibrium wall models improve separation prediction.

Numerical dissipation affects performance differently for attached and separated flows.

Discretization of convective terms is crucial for accurate WMLES results.

Abstract

This work investigates the current wall-modeled large-eddy simulation (WMLES) capabilities of the open-source computational fluid dynamics solver OpenFOAM, which is used widely in academia and industry. This is achieved by a simulation campaign that covers both attached and smooth body separation cases. The campaign includes simulations using four different wall models and aims to investigate the sensitivity of the results to changes in numerics, mesh resolution, and subgrid-scale modeling. The results demonstrate that two main factors largely determine OpenFOAM-based WMLES performance. These are the discretization of the convective term and wall modeling. For the former, the best performance in the attached case is achieved with low-dissipation numerics, however, for the smooth body separation case, more dissipative numerics give the best performance. For the latter, we find that both equilibrium and non-equilibrium wall models perform well in the attached case but that the non-equilibrium models significantly improve the prediction of smooth body separation. Still, the non-equilibrium wall model results do not show a uniform improvement over equilibrium models. This is explained by an inconsistent accounting of non-equilibrium physics in these models, i.e., including the pressure gradient term without also including the convective term. This highlights the potential for future performance improvements by using non-equilibrium wall models that consistently account for both the convective and pressure gradient terms.