The dolphin kick stroke is seen as an important technique used in setting many swimming records because the stroke is used in various races and it has an influence on them. The propulsion of the dolphin kick is determined by a combination of the angles and motions of various joints. We evaluated the knee maximum angle, which is known as one of the most influential factors for propulsion. An evaluation was conducted by computation using the unstructured moving grid finite volume method, which is a highly reproducible approach in the body fitted coordinate system. Furthermore, the approach can prevent accumulation of errors caused by the traveling of grid points. A swimmer model was created using the video footage of a swimmer. To express a traveling swimmer in a pool, the moving computational domain method was adopted. In this method, the motion of the swimmer model itself creates flows around the model instead of putting the model in a uniform flow. Thus, we can calculate acceleration/deceleration and rotational motion of the swimmer model. In this paper, the relationship between the knee joint maximum angle and the ring vortex created by a kick-down motion is also mentioned.

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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.

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