Near-field turbulent simulations of rectangular jets using lattice Boltzmann method

Abstract

We perform large eddy simulation (LES) of the near field of low aspect ratio (AR) rectangular turbulent jets (RTJ) using the lattice Boltzmann method. The computational technique combines a D3Q19 multiple relaxation time (MRT) lattice Boltzmann equation (LBE) with the Smagorinsky model for the subgrid stress. First and foremost, we demonstrate that the MRT-LBE model is more suitable than the widely used single-relaxation-time LBE model for LES of turbulent flows. Then, we proceed to compute four jets with MRT-LBE: AR-1, 1.5, 2, 5; exit velocity u0(m∕s)-60, 39, 60, 23; and Reynolds number Re-184 000, 25 900, 128 000, 14 000. The investigated near-field behavior includes: (1) Decay of mean streamwise velocity (MSV) and inverse MSV; (2) spanwise and lateral profiles of MSV; (3) half-velocity width development and MSV contours; and (4) streamwise turbulence intensity distribution. The simulation results are compared against experimental data. Two unique features of RTJ—the saddle-back MSV spanwise (major axis) profile and axis switching of major axis from spanwise to lateral direction—are investigated. Our simulations show that the jet statistical behavior is more sensitive to inflow velocity and less so to the transverse boundary conditions. Overall, this work demonstrates that the MRT-LBE method is a potentially reliable computational tool for LES of turbulence even at high Reynolds numbers.