Elucidation on constant Strouhal number behind 2-D bluff bodies

点击翻译按钮获取中文摘要

To identify the origin of Karman-vortex street behind 2-D bluff bodies, a new approach was established, which allows to alter the flow dominated by absolute instability from convective instability in subtle variation of the angle of attack of a small NACA0006 airfoil. This approach is based on the fact that the absolute instability is susceptible to the magnitude of separation near the trailing edge of airfoil. In the flow switched from convective to absolute instability at a certain angle of attack, velocity fluctuations abruptly growing with a selected frequency were observed at a certain location behind the airfoil. It could be concluded that the absolutely unstable region is located near this observed point.