Swimming propulsion forces are enhanced by a small finger spread

Department of Sport Sciences, University of Beira Interior, Covilhã, Portugal.
Journal of applied biomechanics (Impact Factor: 0.98). 02/2010; 26(1):87-92.
Source: PubMed


The main aim of this study was to investigate the effect of finger spread on the propulsive force production in swimming using computational fluid dynamics. Computer tomography scans of an Olympic swimmer hand were conducted. This procedure involved three models of the hand with differing finger spreads: fingers closed together (no spread), fingers with a small (0.32 cm) spread, and fingers with large (0.64 cm) spread. Steady-state computational fluid dynamics analyses were performed using the Fluent code. The measured forces on the hand models were decomposed into drag and lift coefficients. For hand models, angles of attack of 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees, with a sweep back angle of 0 degrees, were used for the calculations. The results showed that the model with a small spread between fingers presented higher values of drag coefficient than did the models with fingers closed and fingers with a large spread. One can note that the drag coefficient presented the highest values for an attack angle of 90 degrees in the three hand models. The lift coefficient resembled a sinusoidal curve across the attack angle. The values for the lift coefficient presented few differences among the three models, for a given attack angle. These results suggested that fingers slightly spread could allow the hand to create more propulsive force during swimming.

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    • "From comparisons of the calculated drag forces for quasi-steady (in order to simplify transient flows, the hydrodynamic forces exerted on a body moving unsteadily within a fluid are assumed to be determined at any instant only by the flow field at that instant) and accelerated flow conditions, the authors were able to demonstrate that the drag under accelerated conditions is larger than that for quasi-steady conditions by almost 40%, clearly indicating the need for performing simulations under transient conditions (i.e. in the accelerated flow condition ) instead of adopting the quasi-steady assumption. Following this study, many CFD simulations (Alves, Marinho, Leal, Rouboa, & Silva, 2007; Bilinauskaite, Mantha, Rouboa, Ziliukas, & Silva, 2013; Bixler & Riewald, 2002; Gardano & Dabnichki, 2006; Marinho, Barbosa, Rouboa, & Silva, 2011; Marinho et al., 2009b, 2010; Minetti, Machtsiras, & Masters, 2009) were carried out for the flow around a hand and forearm under steady-state conditions (an object or a body is statically placed in a uniform flow without any body motion); these are listed in Table 1. Although these steady-state simulations are, in principle, capable of estimating the thrust and lift forces, results are limited, as exemplified by Bixler and "
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