2006 Fiscal Year Final Research Report Summary
Role of dynamic lift and its application to the propulsive force in swimming
| Project/Area Number |
15300216
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Sports science
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| Research Institution | University of Tsukuba |
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Principal Investigator |
MATSUUCHI Kazuo University of Tsukuba, Graduate School of Systems and Information Engineering, Professor, 大学院システム情報工学研究科, 教授 (70111367)
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| Co-Investigator(Kenkyū-buntansha) |
NOMURA Takeo University of Tsukuba, Graduate School of Comprehensive Human Sciences, Professor, 大学院人間総合科学研究科, 教授 (80091817)
SAKAKIBARA Jun University of Tsukuba, Graduate School of Systems and Information Engineering, associate Professor, 大学院システム情報工学研究科, 助教授 (10292533)
HASEGAWA Hiroaki Akita University, Faculty of Engineering and Resource Science, Lecturer, 工学資源学部, 講師 (90344770)
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| Project Period (FY) |
2003 – 2006
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| Keywords | swimming / propulsive force / flow visualization / unsteady flow / vortex / momentum |
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| Research Abstract |
Much effort has been devoted to estimating the propulsive force of swimmers in a front crawl. Estimations have typically applied a steady flow theory called quasisteady analysis. Flow fields around a swimmer, however, are extremely unsteady. To elucidate the generation mechanism of force, it is necessary to determine the unsteady properties of flow around a swimmer. In this study, we carefully investigate the flow field that is created around a hand in the front crawl.
The most sophisticated technique for detecting an unsteady flow field is Particle Image Velocimetry (PIV). Measurements were carried out using this technique in several horizontal planes for subjects swimming in a flume. Using this method, one hundred time-sequential flow fields can be obtained at once. Each flow field was calculated from two particle images using cross-correlation method. For estimation for the propulsive force, not only the intensity of vortices ; their location is also important. Vorticity distributions were calculated with respect to the unsteady dynamics because vortices play an essential role in generation of propulsive forces, especially lift force.
Using many time-sequential figures, it was apparent that a strong vortex was generated near the hand. It then shed in the transition phase from in-sweep to out-sweep. After vortex shedding, a new vortex, rotating with opposite direction, was created. The pair of vortices induced the velocity component in the direction opposite to the swimming direction. The momentum change that is attributable to this velocity component is the origin of thrust force by hand.
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