Numerical investigation on characteristic flow regions for three staggered stationary circular cylinders

In this work, the characteristic flow regions for three stationary circular cylinders were numerically investigated by the multiple-relaxation-time (MRT) based lattice Boltzmann method (LBM). The immersed boundary method (IBM) was employed to handle the solid boundary of cylinders to account for the fluid-solid interaction. The cylinders were arranged in a staggered configuration, which means that one cylinder was placed in front of the others with side-by-side arrangement. The calculations were carried out at different spacing ratios T/D (varying from 1 to 10) and fixed spacing ratio S/D=3 with a constant Reynolds number Re=200, which represents a typical unsteady laminar flow. Here, D is the diameter of the cylinders, T is the spacing between the centers of two downstream cylinders, and S is the distance between the centers of the upstream cylinder and downstream cylinders. The experiments based on the laser-induced fluorescence (LIF) flow visualization were performed to verify the reliability of simulation results. The results indicated that the spacing ratio T/D has a significant influence on the wake structures. Two different characteristic steady and unsteady flow regions behind the upstream cylinder were observed. The characteristic steady flow occurs at the regions of 1≤T/D≤1.2 and 2.5≤T/D≤3.1, and the characteristic unsteady flow happens at the regions of 1.3≤T/D≤2.4 and 3.2≤T/D≤10. The present results would be helpful for designing multiple piers in the practical application.