Vortex structure extraction from circular disk wake by POD and PIV processing

Abstract

Vortex structures generated from a bluff body in flow causes noisevibrationand energy loss. Investigation of such vortex structure is useful for solving various engineering problems. The purpose of this study is to extract vortex structures in the wake behind a circular diskas a typical asymmetric bodyby particle image velocimetry (PIV) processing. In order to extract the vortex structure behind the diska Proper Orthogonal Decomposition (POD) was applied to correlation matrix of velocity fluctuation. POD can extract optimally dominant structure in energy contributionwithout subjectively point of view. POD results showed that the first dominant structure was the reverse flow region behind circular disk. This reverse flow region developed to two times of disk diameter in downstream direction. In Snapshot-POD analysiseigenfunctions indicated alternate vortex shedding and connecting structures. These structures were similar to staggered vortices observed in the wake behind the sphere.