Abstract
Numerical solutions of a homogeneous, incompressible and viscous flow past a circular cylinder on an ƒ-plane are presented. A direct comparison is made between published experimental results and the numerical results and shown to be in good agreement. As observed experimentally by Boyer (1970) and Boyer and Davies (1982), the presence of the Ekman friction delays the boundary layer separation. This is because the Ekman friction alleviates the adverse pressure gradient at the surface of the cylinder. It is shown that the eddies initially formed behind the cylinder finally spin-down. The core of these eddies, in contrast to a non-rotating case, becomes almost stagnant in a final state. The drag coefficient Cd is dependent on both Re and α where α is the ratio of the square root of the Ekman number to the Rossby number. It decreases as Re increases at least for 20≤Re≤200 when α is fixed. If Re is kept constant, Cd increases with increasing α. The Stokes's drag law adapted for a rotating fluid is found to be in good agreement with the present numerical result at a small Reynolds number. It is also found that a nonlinear effect (O(R20)) associated with the Ekman suction can generate a noticeable asymmetry (which was observed in the experiments) in the wake when separation occurs.
