Accession Number : ADP008982

Title :   Observations on the Near Wake of a Yawed Circular Cylinder,

Corporate Author : FLORIDA AGRICULTURAL AND MECHANICAL UNIV TALLAHASSEE

Personal Author(s) : Lourenco, L. ; Shih, C. ; Krothapalli, A.

Report Date : 23 JUL 1992

Pagination or Media Count : 9

Abstract : Unsteady characteristics of the near wake of a yawed circular cylinder were studied experimentally in a low speed wind tunnel and in a water towing tank facility using Particle Image Velocimetry (PIV) technique. Four different yaw angles (0, 30, 45 and 60 deg) were tested with Reynolds numbers ranging from 8,000 to 60,000. The detailed wake characteristics are described in terms of instantaneous velocity and vorticity fields obtained at a Reynolds Number of 3,900. Immediately behind the model, large scale vortical structures emerge as a result of shear layer instabilities. The amalgamation of several of these structures leads to the formation of the wake vortices. The eventual shedding of the vortices is a result of the strong interaction between two shear layers separated from the cylinder. The vortex shedding Strouhal number variation with the yaw angle does not follow the Independence Principle for yaw angles beyond 30 deg. Using momentum balance concept, the unsteady forces on the model are determined and are found to agree with established results. (Author)

Descriptors :   *WAKE, FLOW FIELDS, ANGLE OF ATTACK, CYLINDRICAL BODIES, REYNOLDS NUMBER, VELOCIMETERS, UNSTEADY FLOW, YAW, SHEAR PROPERTIES, VORTEX SHEDDING, STROUHAL NUMBER.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE