VORTICITY MEASUREMENTS IN THE NEAR WAKE OF A CIRCULAR-CYLINDER AT LOW REYNOLDS-NUMBERS

The technique of the particle streak method has been applied to the study of bluff-body wakes at low Reynolds number. Vorticity and shear stress were measured to an accuracy of 15-20%. The vortex shedding cycles at Reynolds number of 73 and 226 are shown and the differences between the two are highlighted. Quantitative descriptions of the previously described vortex splitting phenomenon in the near wake are made, which leads to a description of the vortex shedding mechanism at low Reynolds number. The definition of low-Reynolds-number formation region length is examined. The strength of shed vortices obtained from integration of the vorticity is compared with directly measured vortex strengths and with the results of two-dimensional numerical analysis.