Flow about a circular cylinder with a single large-scale surface perturbation

✍ Scribed by J. Nebres; S. Batill

• Publisher: Springer
• Year: 1993
• Tongue: English
• Weight: 948 KB
• Volume: 15
• Category: Article
• ISSN: 0723-4864
• DOI: 10.1007/bf00191775

✦ Synopsis

An experimental study of the flow around a cylinder with rms a single straight perturbation was conducted in a wind tunnel. With this bluff body, positioned in a uniform crossfiow, the vortex shed-S ding frequency and other flow characteristics could be manipulated, Smax The Strouhal number has been shown to be a function of the perturbation angular position, 0p, as well as the perturbation size Smi, t and Reynolds number. As much as a 50% change in Strouhal Uc number could be achieved, simply by changing 0p by 1 ~ The perturbation size compared to the local boundary layer thickness, 6, Umax was varied from approximately 1 6 to about 206. The Reynolds U~ number was varied from 10,000 to 40,000. For perturbation sizes U~c approximately 5 6 to 20 fi and Reynolds numbers of 20,000 to 40,000, x a consistent Strouhai number variation with 0 r was observed.

A detailed investigation of the characteristic Strouhal number z variation has shown that varying 0p had a significant influence on the boundary layer separation and transition to turbulence. These Ax significant changes occurring in the boundary layer have been A~ shown to cause variations in the spacing between the shear layers, base pressure, drag, lift, and the longitudinal spacing between the vortices in the vortex street.

List of symbols

a Cd Cac C, Cp C,,b C pbr d d* D