Numerical investigation of flow past single and tandem cylindrical bodies in the vicinity of a plane wall

Abstract

A numerical study has been conducted to investigate the behavior of the vortical wake created by square and circular cylinders placed in a boundary-layer flow formed over a plane wall. The calculations are performed by solving the unsteady two dimensional (2-D) Navier–Stokes equations with a finite volume method at low Reynolds numbers, Re=100 and 200. Apart from the Reynolds number the flow field characteristics also depend on distance of the cylinder from the plane wall and longitudinal gap between two cylinders, L. To study the effect of gap (G) between the cylinder and the wall, calculations are performed at various gap ratios (g⁎). Gap ratio is defined as the ratio of the gap (G) and the characteristic cross-stream dimension of the cylinder. In the case of square cylinder the characteristic dimension is the length of a side of the cylinder (H) and in the case of a circular cylinder the dimension is the cylinder diameter (D). The vorticity in the boundary layer formed over the plane wall interacts intensely with the vorticity associated with the shear layer emanating from the separation points on the cylinder surface and produces a complex flow field in the wall gap and the cylinder wake. An attempt has been made to analyze these complex flow features through numerical flow visualization tools like vorticity contours and streamlines.