Effects of Free stream Disturbance on the Development of the Compressible flow around a square cylinder at Subsonic Mach Numbers

摘要

The three-dimensional Navicr-Stokcs equations are numerically solved to study the effects of free stream disturbances on the evolution of the compressible wake of a square cylinder and on the resultant three-dimensional wake structures. Spatially evolving wake flows with free stream Mach number of 0.3 and Re up to 200 are simulated. The relation between the vortex dynamics and the sound emitted in the three-dimensional wake is analyzed. The numerical results provide new physical insights into three-dimensional structures in a transitional wake. Upstream disturbance conditions play an important role for the evolution of the transitional structures of the wake. The sound emission in the three-dimensional flow around a uniform cross-section square cylinder is principally characterized as dipolar nature. The lift force doe to the pressure difference between the upper and lower sides of the cylinder varies alternatively, even though the pressure spanwise distribution varies on the upper or lower side varies, which is attributed to alternative vortex shedding.