Vortex shedding characteristics of flow past two different diameters cylinders in tandem arrangement at low Reynolds number

Flow vortex shedding from two circular cylinders of different diameters in tandem arrangement is investigated by means of numerical simulations. The two-dimensional Navier-Stokes equations are solved by a fractional step upstream finite element method at a relatively low Reynolds number Re = 100. The studied Reynolds number based on the diameter of the downstream main cylinder. The diameter of the downstream main cylinder was kept constant, and the diameter ratio between the upstream control cylinder and the downstream one was varied from 0.1 to 1.0. The gap between the control cylinder and the main cylinder ranged from 0.1 to 4.0 times the diameter of the main cylinder. It is concluded that the gap ratio and the diameter ratio between the two cylinders have important effects on vortex shedding characteristics from two cylinders of different diameters in a tandem arrangement.