Three dimensional numerical simulation of flow around four circular cylinders in an in-line square configuration

Uniform flow past four circular cylinders in an in-line square configuration was studied numerically at Reynolds number of 270. The three-dimensional (3D) Navier-Stokes equations were solved using OpenFOAM, an open source code. The study was focused on the influence of multiple cylinders and their spacing ratio on the wake flow. The effects of gap between two neighbor cylinders on vortex shedding frequency and force coefficients are studied. Flow characteristics are observed through flow visualization of streamwise and spanwise vortices based on the numerical results. It was found that there exists remarkable repulsive force when cylinders are very close to each other, and this repulsive force disappears gradually with the increase of spacing ratio. Also, the critical Reynolds number for flow transiting from two-dimensional to three-dimension is different from that of an isolated cylinder and is dependent on gap among the cylinders.