Clarification of Unsteady Fluid Forces Acting on Limbs in Swimming Using an Underwater Robot Arm

摘要

The objective of this study was to clarify the unsteady characteristics of the fluid forces acting on limbs during swimming. For this objective, an underwater robot arm was developed in this paper. The robot arm has five degrees-of-freedom in order to perform the various complicated limb motions during swimming. In addition, by changing the hand replica into the foot one, the robot also can perform the lower limb motions. The joint torques and the resultant thrust can be measured by the force sensors attached to the robot. In a circulating water tank, an experiment to measure the fluid forces was conducted for four swimming strokes of the upper and lower limbs. From the experiment, it was found that even the slight difference of the fluid forces between slightly different swimming motions can be quantified by the developed experimental system. In addition, it was suggested that ‘nipping’ the water by both lower limbs during the kick of the breaststroke almost does not affect thrust generation. The developed experimental system with the robot arm is useful not only for measuring the unsteady fluid forces, but also for flow visualization in future studies.