The effect of finger spreading on drag of the hand in human swimming |
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| Affiliation: | 1. Department of Applied Physics, Eindhoven University of Technology and J.M. Burgers Centre for Fluid Dynamics, Postbus 513, 5600 MB Eindhoven, The Netherlands;2. Laboratory for Aero and Hydrodynamics, Delft University of Technology and J.M. Burgers Centre for Fluid Dynamics, 2628 CD Delft, The Netherlands;1. Dipartimento di Ingegneria Civile e Industriale, University of Pisa, Italy;2. Finnish Meteorological Institute, Finland;1. Institute of Continuous Media Mechanics, Ural Division, Russian Academy of Sciences, Perm 614013, Russia;2. Leibniz-Institut für Polymerforschung Dresden e.V., Dresden 01069, Germany;3. Technische Universität Dresden, Institut für Werkstoffwissenschaft, Dresden 01069, Germany;1. Carnegie Mellon University in Qatar, P.O. Box: 24866, Doha, Qatar;2. Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824, United States;1. Barcelona Microelectronics Institute, IMB-CNM (CSIC), 08193 Bellaterra, Spain;2. Institut de Bioenginyeria de Catalunya (IBEC), 08028 Barcelona, Spain;3. Departament d’Electrònica, Universitat de Barcelona, 08028 Barcelona, Spain;1. Univ. Orleans, Ensi de Bourges, PRISME EA4229, F45072 Orléans, France;2. Univ. Bretagne Sud, LIMATB, Rue Saint-Maudé, Centre de Recherche BP92116, F56321 Lorient, France |
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| Abstract: | The effect of finger spread on overall drag on a swimmer’s hand is relatively small, but could be relevant for elite swimmers. There are many sensitivities in measuring this effect. A comparison between numerical simulations, experiments and theory is urgently required to observe whether the effect is significant. In this study, the beneficial effect of a small finger spread in swimming is confirmed using three different but complementary methods. For the first time numerical simulations and laboratory experiments are conducted on the exact same 3D model of the hand with attached forearm. The virtual version of the hand with forearm was implemented in a numerical code by means of an immersed boundary method and the 3D printed physical version was studied in a wind tunnel experiment. An enhancement of the drag coefficient of 2% and 5% compared to the case with closed fingers was found for the numerical simulation and experiment, respectively. A 5% and 8% favorable effect on the (dimensionless) force moment at an optimal finger spreading of 10° was found, which indicates that the difference is more outspoken in the force moment. Moreover, an analytical model is proposed, using scaling arguments similar to the Betz actuator disk model, to explain the drag coefficient as a function of finger spacing. |
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| Keywords: | Human swimming Hydrodynamics CFD Finger spreading Swimming efficiency |
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