Study Of The Drag And Optimization Analysis On Propulsion In Swimming

This paper has made study on the experimental measuring, numerical simulation and theoretical derivation of swimming optimization, which includes details as following:Because of the difficulty in directly measuring the active drag in swimming, this paper designed a set of system-Additive Small Drag Method to measure it indirectly, which can be used as a training device also. During the measurement, the subject was asked to propel at full tilt with and without the small drag and the corresponding average velocities were computed. When a small drag was attached to the subject in swimming, its variation was recorded as an analog signal through a force transducer and a tape recorder. With the help of sampling and power spectrum estimation, we analyzed the frequency and amplitude character and pointed out its relationship with the stroke frequency. Furthermore, an experiential formula was put forward to describe the variation of active drag. Finally, the average active at the maximal velocity in frontal crawl was calculated.There have been many experiments testing passive drag on human bodies in swimming, while the numerical simulation has not been used to compute it. This paper built a simplified geometric model of the human body according to the dimension pool of Chinese human bodies and estimated the passive drag in gliding with the commercial software "Fluent". As a result, it was found that the change tendency compared well with previous experiment. Further study manifests that the drag coefficients has the hyperbola character. Namely, it decreases as the velocity increases and drive to a steady value monotonically.In order to clarify the bifurcation that it should or not splay fingers in swimming, this paper has applied the numerical simulation technique. Based on the model of palm and fingers, the drags and corresponding coefficients were calculated in the case of different angles of flare and different angles of attack. As a result, it indicated that the more the flare angles the less the drag. Then we advised that athletes should shut theirs fingers and make larger angle of attack during the course of stroke.A model was created to describe the dynamics and energy conversion in short distance competitive swimming. Based on some hypotheses and constraints, the study made an optimization analysis of the distance traveled in a given time with optimal control theory. Using the records of the 27th Olympics and the results from previous research, an optimal solution of propulsion was derived. Correspondingly, the optimal "three stage" tactic for velocity distribution was put forward, which was in agreement with the practice.