Abstract
Stably stratified flows past a two-dimensional hill in a channel of finite depth are analyzed numerically by using a newly-developed multi-directional finite-difference method at a Reynolds number of 2000 based on the freestream velocity U and the obstacle's height h. Attention is focused on unsteady characteristics of the flow around the hill for the cases of 1<K (=NH/πU) 2 (strong stratification) where N and H are the buoyancy frequency and the domain depth. The numerical results clarify that the periodical change in the flow around the hill, which leads to a persistent Cd oscillation, is caused by the detaching of the upstream advancing columnar disturbance with mode n=1. Furthermore, it is shown that the unsteadiness in the flow is strongly affected by the Reynolds number, the blockage ratio H/h and the body shape.
