Investigation of Aerodynamic Characteristics of Circular Cylinders under Streamwise Pressure Gradients

摘要

Flows around circular cylinders under streamwise pressure gradients were studied experimen- tally. Pressure distributions on the cylinder surface, frequencies of shedding vortices and wake velocity distributions were obtained under the various pressure gradients. The fundamental charac- teristics of flows around the circular cylinders, such as pressure distributions on the cylinders, angles of separation, pressure drags as well as velocity profiles and turbulence in the wake flows, exhibit remarkable discontinuous changes at a specific value of pressure gradient. The specific pressure gradient, which may be called “critical pressure gradient”, is proved to be around X_cr= (dp/dx)/(ρU~2_0 /2d)≈0.05, independently of Reynolds numbers. The vortex shedding vanishes under the pressure gradient more than X_cr.