Simulation of Flow Around a Cube at Moderate Reynolds Numbers Using the Lattice Boltzmann Method

This article reports flow behavior around a suspended cube obtained using three-dimensional (3D) lattice Boltzmann method (LBM)-based simulations. The Reynolds number (Re) range covered is from 84 to 770. Four different flow regimes are noted based on the flow structure in this range of Re: steady axisymmetric (84 ≤ Re ≤ 200), steady nonaxisymmetric (215 ≤ Re ≤ 250), unsteady nonaxisymmetric in one plane and axisymmetric in the other plane (276 ≤ Re ≤ 300), and unsteady nonaxisymmetric in streamwise orthogonal planes (339 ≤ Re ≤ 770). Recirculation length and drag coefficient follow inverse trend in the steady flow regime. The unsteady flow regime shows hairpin vortices for Re ≤ 300 and then it becomes structureless. The nature of force coefficients has been examined at various Reynolds numbers. Temporal behavior of force coefficients is presented along with phase dependence of side force coefficients. The drag coefficient decreases with increase in Reynolds number in the steady flow regime and the side force coefficients are in phase. Drag coefficients are compared with established correlations for flow around a cube and a sphere. The side force coefficients are perfectly correlated at Re = 215 and they are anticorrelated at Re = 250. At higher Reynolds numbers, side force coefficients are highly uncorrelated. This work adds to the existing understanding of flow around a cube reported earlier at low and moderate Re and extends it further to unsteady regime at higher Re.