Abstract
Vortex structure and drag characteristic of a circular cylinder accelerated from a rest were investigated by flow visualization and drag measurement. The circular cylinder submerged in a water tank was moved with a constant acceleration by using a linear-motor actuator system. The vortex structure in the wake of cylinder was visualized by using dye and particles method. The drag was measured by using a load cell. The formation process of the twin vortex was observed during accelerated motion. The twin vortex behind the circular cylinder showed bilaterally symmetric at initial stage, and collapsed afterwards. The secondary vortex formed near the separation point. The vorticity flux of twin vortex was calculated by using the photographs of flow visualization. These results provided the effect of the vortex structure on time evolution of the drag.
