Features of flow around the leading edge of a circular cylinder

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

Axial flow over a circular cylinder is very complex, particularly around the leading edge of the cylinder, comprising separation bubble/cavitation, shear-layer reattachment, etc. Pressure fluctuations in the separation region may induce structural vibrations and generate noise. This paper presents the results of wall pressure measurement and flow visualization done around the cylinder leading edge with blunt, conical and hemispherical noses at Reynolds number (ReD, based on cylinder diameter D) ranging from 1.5 × 103 to 4.2 × 104. The yaw angle is varied from 0° (axial) to 3.5°. Attention has been paid to investigate the effects of nose shape, ReD and on the flow features as well as time-mean pressure coefficient Cp and fluctuating (rms) pressure coefficient Cp . At = 0°, blunt nose engenders longer reattachment length xR, wider bubble width W and shorter transition length xTr, compared with conical and hemispherical noses. Cp and Cp’ are found to be highly sensitive to ReD for hemispherical nose. Blunt nose presents highest Cp’, while hemispherical nose corresponds to the lowest Cp’. With increasing from 0° to 3.5°, Cp declines and Cp’ increases for both blunt and conical noses, while those for hemispherical nose vary less regularly. A slight increase in influences the flow separation with enhanced XR and W, and reduced XTr for all the three noses.