Three-dimensional simulation of flow past two circular cylinders of different diameters

The vortex shedding flow past two circular cylinders of different diameters is investigated numerically by solving the threedimensional Naiver-stokes equations using the Petrov-Galerkin finite element method (PG-FEM). The Reynolds number based on the free stream velocity (U) and the diameter of the large cylinder (D) is Re=1000. Simulations are carried out for a constant gap of 0.0625D and a constant diameter ratio of 0.45. The study is focused on the effect of position angle of small cylinder relative to the larger one on the three-dimensional flow, the force coefficients, the vortex shedding frequencies from the two cylinders and flow characteristics. As observed in the previous experimental studies, biased flow in the wake of the gap is observed when the two cylinders are in nearly side-by-side arrangement and it leads to significant reduction of the oscillation of the forces on the cylinders.