Synthetic turbulence generator for lattice Boltzmann method at the interface between RANS and LES

TL;DR

This paper introduces a synthetic turbulence generator for the lattice Boltzmann method to effectively simulate turbulent flows at the RANS-LES interface, demonstrating good accuracy and computational efficiency.

Contribution

The paper presents a novel synthetic turbulence generator integrated with LBM for RANS-LES interface, improving turbulence simulation accuracy and efficiency.

Findings

Good agreement with DNS and LES-LBM results

Fast and robust turbulence generation method

Effective at short adaptation lengths and times

Abstract

The paper presents a synthetic turbulence generator (STG) for the lattice Boltzmann method (LBM) at the interface of the Reynolds averaged Naiver-Stokes (RANS) equations and the LBM Large Eddy Simulation (LES). We first obtain the RANS velocity field from a finite volume solver at the interface. Then, we apply a numerical interpolation from the RANS velocity field to the LBM velocity field due to the different grid types of RANS and LBM. The STG method generates the velocity fluctuations, and the regularized LBM reconstructs the particle distribution functions at the interface. We perform a turbulent channel flow simulation at Re_{\tau} = 180 with the STG at the inlet and the pressure-free boundary condition at the outlet. The velocity field is quantitatively compared with the periodic lattice Boltzmann based LES (LES-LBM) channel flow and the direct numerical simulation (DNS) channel flow. Both adaptation length and time for the STG method are evaluated. Also, we compare the STG-LBM channel flow results with the existing LBM synthetic eddies method (SEM-LBM) results. Our numerical investigations show good agreement with the DNS and periodic LES-LBM channel flow within a short adaptation length. The adaptation time for the turbulent channel flow is quantitatively analyzed and matches the DNS around 1.5 to 3 domain flow-through time. Finally, we check the auto-correlation for the velocity components at different cross-sections of the streamwise direction. The proposed STG-LBM is observed to be both fast and robust. The findings show good potential for the hybrid RANS/LES-LBM based solver on the aerodynamics simulations and a broad spectrum of engineering applications.