Relation between drag characteristic and vortex structure of accelerating cylinder from a rest

Abstract

The purpose of this study is to understand the relationship between the vortex structure and the drag characteristic of a circular cylinder during accelerated motion from a rest. Wake flow of the accelerated circular cylinder was visualized by fluorescent dye technique. Drag act on the accelerated cylinder was determined by the measurement device using an expansion coil. The development of a twin vortex separated from the cylinder was observed during the accelerated motion. At the beginning of the accelerated motion, drag showed sudden change at the same time that the twin vortex collapsed temporarily. Then the twin vortex was gradually grown by supplying vorticity of shear layer vortices. We confirmed that drag coefficient of accelerated circular cylinder was influenced depending on the accelerations. © 2013 The Japan Society of Mechanical Engineers.