Effects of leading edge geometry on the vortex shedding frequency of an elongated bluff body at high Reynolds numbers

摘要

Measurements have been performed in a large scale wind tunnel on an elongated bluff body with a chord-to-thickness ratio of 7 over the Reynolds number range Re=4.0-7.5 x 10~4. Six different leading edge separation angles were created by altering the leading edge geometry. Time-resolved, synchro-nized, surface pressure and Particle Image Velocimetry data allow for detailed characterization of the flow around the body and in the recirculation region. The results show a linear decrease in the shedding frequency of nearly 40% as the leading edge separation angle is increased from 0°-90°. The PIV data are phase averaged in the recirculation region and the convection speed of the vortices is characterized. From the phase averaged data, the velocity outside of the recirculation region is observed to decrease markedly as the leading edge separation angle is increased, which is suggested to be responsible for the observed changes in the shedding frequency.