Numerical simulation of flow around human in underwater dolphin kick swimming

Abstract

Dolphin kick swimming is an underwater undulatory motion which is similar to the way dolphin and other cetaceans swim, and it's utilized after dives and turns in competitive swimming. Since in the international rules underwater limit is 15m which is 30% of 50m pool, this swimming technique has large effect on swimming records. Thus, it is essential to know and control fluid dynamics of dolphin kick swimming. In this paper, flow around human in dolphin kick swimming is simulated and the results are evaluated. To implement the simulation, dolphin kick movement is reproduced on computer by 3D model of male swimmer and changes of 5 joint angles are captured from the video footage, and the flow around swimmer model is computed by means of a moving grid finite volume method. This computational approach completely fulfills geometric conservation laws, so that moving boundary problems become resolvable. Also, a moving computational domain method actualizes unrestricted move of swimmer model. Furthermore, coupling of these methods and kinematics allows swimmer model to dynamically accelerate and decelerate by the forces applied to itself. The result shows that most of the thrust is produced in down-kick, and the ring vortex is generated in the wake, which appears in practical dolphin kick swimming. And the speed of swimmer model agrees with the speed of swimmer in the video footage.