A Hydrodynamic Study of Active Drag in Swimming

Abstract

The purpose of this study is to measure active drag, which is dynamic drag acting on a self-propelling swimmer in water. We developed a new measurement device, which was capable of measuring active drag without disturbing natural swimming in a circulating water channel. Four collegiate skilled swimmers volunteered to participate in this study. The subjects were asked to swim front crawl and to keep the pre-determined stroke frequency within a range of 0 m / s to 1.8 m / s flow velocity. The active drag was estimated by means of the relationship between residual thrust(thrust minus the resistance)and passive drag(static drag acting on a prone position swimmer). As a result of these development, it was possible to measure active drag more precisely than before, and to obtain the experimental equation that predicted the active drag within a range of Reynolds number equaled the actual swimming velocity.