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

(2nd Report, Modeling of Fluid Force Using Experimental Results)

Abstract

The objective of this study was to clarify the unsteady characteristics of the fluid force acting on limbs during swimming. For this objective, an underwater robot arm, which has five degrees-of-freedom in order to perform the various complicated limb motions during swimming, was developed. In the previous study, an experiment to measure the unsteady fluid force was conducted for four swimming strokes of the upper and lower limbs. In this paper, the unsteady fluid force model was firstly formulated. Second, the simulation of experimental conditions was conducted. Two fluid force coefficients, which are the parameters in the fluid force model, were identified using optimizing calculation, so that the discrepancies of the forces and moments between the experiment and simulation were minimized. In addition, fluid force models which are dependant only on the limbs’ shapes were determined. Good agreement between the experiment and simulation with the determined fluid force model indicated the validity of the determined model. The identified fluid model will be useful for mechanical analyses of various swimming motions in future studies.