Flux-controlled wall model for large eddy simulation integrating the compressible law of the wall

TL;DR

This paper introduces a flux-controlled wall model for LES that directly adjusts wall shear stress and heat flux using a control strategy based on the compressible law of the wall, improving accuracy and efficiency in turbulent flow simulations.

Contribution

The paper presents a novel flux-controlled wall model for LES that bypasses boundary layer equations, enhancing accuracy in compressible turbulent flows with reduced computational cost.

Findings

Achieves less than 4.1% error in friction coefficient across tested cases.

Reproduces mean velocity and temperature profiles in agreement with DNS data.

Outperforms conventional models in accuracy for compressible turbulent channel flows.

Abstract

Recent advances in velocity and temperature transformations have enabled recovery of the law of the wall in compressible wall-bounded turbulent flows. Building on this foundation, a flux-controlled wall model (FCWM) for Large Eddy Simulation (LES) is proposed. Unlike conventional wall-stress models that solve the turbulent boundary layer equations, FCWM formulates the near-wall modeling as a control problem applied directly to the outer LES solution. It consists of three components: (1) the compressible law of the wall, (2) a feedback flux-control strategy, and (3) a shifted boundary condition. The model adjusts the wall shear stress and heat flux based on discrepancies between the computed and target transformed velocity and temperature, respectively, at the matching location. The proposed wall model is evaluated using LES of turbulent channel flows across a broad range of conditions, including quasi-incompressible cases with bulk Mach number \(M_b = 0.1\) and friction Reynolds number \(Re_\tau = 180 \sim 10{,}000\), and compressible cases with \(M_b = 0.74 \sim 4.0\) and bulk Reynolds number \(Re_b = 7667 \sim 34{,}000\). The wall-modelled LES reproduce mean velocity and temperature profiles in agreement with direct numerical simulation data. For all tested cases with \(M_b \leq 3\), the wall model achieves relative errors of \(|\epsilon_{C_f}| < 4.1\%\), \(|\epsilon_{B_q}| < 2.7\%\), and \(|\epsilon_{T_c}| < 2.7\%\) in friction coefficient, non-dimensional heat flux, and centerline temperature, respectively. In the quasi-incompressible regime, the wall model achieves \(|\epsilon_{C_f}| < 1\%\). Compared to the conventional equilibrium wall model, the proposed FCWM achieves higher accuracy in compressible turbulent channel flows without solving the boundary layer equations, thereby reducing computational cost.