Flow Separation of a Rotating Cylinder
The effects of rotating a circular cylinder on the suppression of flow separation were investigated experimentally. Flow separation and vortex shedding were studied by flow visualization to guide the hot-film anemometry measurements that follow. The experiments were conducted for flow past a circular cylinder with an aspect ratio of 16 in a recirculating water channel at Reynolds numbers in the range of 140 to 1,000. The rotational to translational speed ratio, α, varied from 0 to 5. The present results show the existence of a critical α value of about 2.3 at which the vortex shedding is suppressed. Below this critical value of α, the Kármán vortex street and separation points are observed. Vortex shedding is deflected and separation points are displaced more and more towards the rotation direction of the cylinder as α increases. Above the critical α value, vortex shedding disappears. The two separation points on the cylinder surface seem to move very close to each other at α > 2.3. This issue will also be discussed by analyzing the flow pictures obtained from flow visualization. The flow regime close to the cylinder surface is analyzed at different Reynolds numbers and different values of α to study how the cylinder's rotation affects the flow separation. The effects of rotating circular cylinder to vortex shedding frequency as well as the suppression of vortex shedding and flow separation are studied in order to understand the moving-wall effects in flow separation control.
KeywordsFlow separation Vortex shedding suppression Rotating circular cylinder Magnus effect
One of the authors (T.T.L. Duong) is a Ph.D. student and recipient of a graduate scholarship from the National University of Singapore. This scholarship is gratefully acknowledged.