Observation of the Flows Around a Circular Cylinder with the Photographs Taken in a Long Exposure Time

Flows around a circular cylinder which is stationary, rotating, or oscillating in a uniform flow have been visualized by hydrogen bubble techniques. The photographs of the flows are taken in a long exposure time in order to make clear the timeaveraged characteristics of the flows. The shapes of the streamlines near the stagnation point and the separation points of the cylinder can be determined accurately by analyzing these photographs. Time-averaged patterns of the near wake of the oscillating cylinder are obtained and the relation between these patterns and the drag of the cylinder is discussed.