Coefficient of drag in japanese competitive swimmers

Abstract

The purpose of this study was to obtain and standardize the drag coefficients of the bodies under water of Japanese competitive swimmers. This study was made with the cooperation of 33 Japanese competitive swimmers (24 males and 9 females at the mean age of 18.9±5.7-yrs.). The physical features of each swimmer were measured before the experiment. Each swimmer was towed 20 meters at five speeds under the water in a swimming pool, using a "reel-up system" developed by Nomura et al.(1994). The swimmer maintained a "gliding position" while being towed. The posture of the swimmer was recorded using two underwater video cameras. The output data on the towing speed and drag from the reel-up system were entered into a personal computer for operational processing. As a result of this analysis, it turned out that were the significant correlations between the drag and the cross-sectional area (Ac), the surface area (As), the 0.667 power of the volume (7/3) of the swimmer. Therefore, Ac, As and ∇^lt2/3gt of the body were adopted as a representative area, and the drag coefficient was calculated using the following equation (1). Cd = 2R/ρSV^2 (1). Each representative average of the drag coefficients depends on a representative area (Ac:Cd=0.789±0.096, As:Cd=0.030±0.003, ∇^lt2/3gt:Cd 0.338±0.032). There was no correlation between the drag coefficient and the best record of each swimmer. Consequently, the result of this experiment is summed up as follows. It can be said that although the passive drag of the human body under water is closely related to the area of the body, the value of the drag coefficient has no direct effect on the swimming record.