Application of theoretical principles to swimsuit drag reduction

This study investigated the basic fluid mechanics associated with the hydrodynamic drag of a human. The components of drag (frictionDSF, pressureDP and waveDW) on a human swimmer were analysed by applying classical fluid dynamic fundamentals. General methods of reducing drag were considered and the most probable method identified, applied and tested on swimsuit hydrodynamic drag. This study employed turbulators, either one (upper back) or three (across the upper back, the chest and across the buttocks), that were compared to an identical full body suit with no turbulators. Male and female elite competitive swimmers (n = 7 each) were towed in an annular pool to determine passive drag at speeds from 0.4 to 2.2 m s−1. The total drag was reduced by 11–12% by one turbulator and 13–16% by three turbulators. The total drag was decomposed intoDSF, DP andDW to determine the mechanisms responsible for the reduced total drag by the turbulators. The presence of the turbulators did not significantly increase friction or wave drag; however, flow was attached to the body as there was a significant reduction in pressure drag (19–41%), with the greatest reduction being for three turbulators (chest, back, buttocks). This study demonstrated the importance of pressure drag in determining total drag at high human swimming speeds, and that drag reducing technology can significantly reduce it, in this case by appropriately sized and placed turbulators.