Structure of turbulent leading-edge separation bubble of a blunt circular cylinder ans its response to sinusoidal disturbances

• Published in: Journal of wind engineering and industrial aerodynamics Vol. 49; no. 1-3; pp. 227 - 236
• Main Authors: Kiya, M., Mochizuki, O., Ido, Y., Kosaku, H.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.1993
• ISSN: 0167-6105; 1872-8197
• DOI: 10.1016/0167-6105(93)90018-J

The leading-edge separation bubble of a blunt circular cylinder was forced by a sinusoidally oscillating jet issued from a thin slit along the separation edge. Reynolds number based on the main-flow velocity U∞ and the diameter of the cylinder d was in a range of 4000 – 9500. The level of the forcing was defined at a position near the edge where the time-mean velocity attained a maximum value. The time-mean and r.m.s. velocities in the separation bubble were measured by a two-colour four-beam Laser Doppler Velocimeter. A secondary separation zone was found in the separation bubble, and its length decreased with increasing Reynolds number. The reattachment length of the forced separation bubble decreased with decreasing forcing frequency in a range (2.5–8.5) U∞d, probably attaining a minimum at a smaller forcing frequency.