Abstract
The purpose of this study is to clarify the mechanism of decreasing the drag in natural swimming of fish, whale and dolphin. A cylinder which has Elasto-flexible surface simplified marine creature was placed in a water tunnel, and using Laser Light Sheet method to visualize flow field around the model, vortex pair shedding period from the model, deformation of its cross-sectional form and hydrodynamical drag of the model were simultaneously measured. As a result, the following were found: the rigid front flexible rear cylinder model has showed about 20% higher St number than rigid cylinder model. The local deformation of the surface changed local flow pattern and wake due to some interaction between flexible surface and vortex. Time variation of the drag of the Rigid Front Flexible Rear Cylinder (RFFRC) became smaller than rigid one.
