Separation and free-streamline flows in a rotating fluid at low Rossby number

The flow past a circular cylinder in a rotating frame is examined when the Rossby number Ro is O(E^½), where E is the Ekman number. Previous studies of the configuration have shown that, provided the ratio R_o/E^½is less than a certain critical value, the flow around the cylinder is determined by the classical potential-flow solution. However, once Ro/E^½ is greater than that critical value the E^½layer on the surface of the cylinder, which is rather like a boundary layer in a high-Reynolds-number non-rotating fluid, can separate from the cylinder and distort the potential flow. In this study the form of the flow once separation has occurred is examined using a method analogous to the Kirchhoff free-streamline theory in a non-rotating fluid. The results are compared with published experimental and numerical data on the flow for various values of Ro/E^½.