Article

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

ABSTRACT

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.

Download full-text

Full-text

Available from: A. Rouboa
  • Source
    • "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 "
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper reviews unsteady flow conditions in human swimming and identifies the limitations and future potential of the current methods of analysing unsteady flow. The capability of computational fluid dynamics (CFD) has been extended from approaches assuming steady-state conditions to consideration of unsteady/transient conditions associated with the body motion of a swimmer. However, to predict hydrodynamic forces and the swimmer's potential speeds accurately, more robust and efficient numerical methods are necessary, coupled with validation procedures, requiring detailed experimental data reflecting local flow. Experimental data obtained by particle image velocimetry (PIV) in this area are limited, because at present observations are restricted to a two-dimensional 1.0 m(2) area, though this could be improved if the output range of the associated laser sheet increased. Simulations of human swimming are expected to improve competitive swimming, and our review has identified two important advances relating to understanding the flow conditions affecting performance in front crawl swimming: one is a mechanism for generating unsteady fluid forces, and the other is a theory relating to increased speed and efficiency.
    Full-text · Article · Dec 2015 · Journal of Sports Sciences
  • Source
    • "In the front-crawl technique, the majority of the propulsive force is generated by the swimmer's arm action (Berger, de Groot, & Hollander, 1995; Deschodt, Arsac, & Rouard, 1999). Most studies that have attempted to estimate the amount of propulsion generated by the arms have focussed on the hand (Gourgoulis et al., 2008; Marinho et al., 2010) or the hand together with the forearm (Berger, Hollander, & de Groot, 1999; Bixler & Riewald, 2002; Rouboa, Silva, Leal, Rocha, & Alves, 2006). The motion of the upper arm is not generally thought to contribute to propulsion in able-bodied front-crawl swimming. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract This study examined changes in the propulsive force and stroke parameters of arm-amputee and able-bodied swimmers during tethered swimming. Eighteen well-trained female swimmers (nine unilateral arm amputees and nine able-bodied) were videotaped performing maximal-effort 30 s front-crawl swims, while attached to a load cell mounted on a pool wall. Tether force, stroke rate, stroke phase durations and inter-arm angle were quantified. The able-bodied group produced significantly higher mean and maximum tether forces than the amputee group. The mean of the intra-cyclic force peaks was very similar for both groups. Mean and maximum tether force had significant negative associations with 100 m swim time, for both groups. Both groups exhibited a similar fatigue index (relative decrease in tether force) during the test, but the amputees had a significantly greater stroke rate decline. A significant positive association between stroke rate decline and fatigue index was obtained for the able-bodied group only. Inter-arm angle and relative phase durations did not change significantly during the test for either group, except the recovery phase duration of the arm amputees, which decreased significantly. This study's results can contribute to the development of a more evidence-based classification system for swimmers with a disability.
    Full-text · Article · May 2014 · Journal of Sports Sciences
  • Source
    • "can increase about 10% by the optimization. With the similar approach using Fluent® in a steady state condition, flows around a hand of an Olympic swimmer were analyzed with different thumb positions (Marinho et al., 2009) and with different degrees of the small-finger spread (Marinho et al., 2010), Marinho et al. (2011) also analyzed flow around a hand and forearm of an elite swimmer, and Bilinauskaite et al. (2013) investigated the influence of finger position and orientation of hand on drag and lift forces, although no validations were undertaken in these research. As described above, although CFD has been applied to the analysis of flow around a hand, all of them are in steady state condition, except one study (Rouboa et al. 2006). "
    [Show abstract] [Hide abstract]
    ABSTRACT: A stroke-analysis system based on a CFD (Computational Fluid Dynamics) simulation has been developed to evaluate the hydrodynamic forces acting on a swimmer’s hand. Using the present stroke-analysis system, a stroke technique of top swimmers can be recognized with regard to the hydrodynamic forces. The developed analysis system takes into account the effect of a transient stroke motion including acceleration and a curved stroke path without using assumptions such as a quasi-static approach. An unsteady Navier-Stokes solver based on an unstructured grid method is employed as the CFD method to calculate a viscous flow around a swimmer’s hand which can cope with the complicated geometry of hands. The CFD method is validated by comparison with experiments in steady-state and transient conditions. Following the validations, a stroke-analysis system is proposed, in which a hand moves in accordance with a stroke path measured by synchronized video cameras, and the fluid forces acting on the hand are computed with the CFD method. As a demonstration of the stroke-analysis system, two world class swimmers’ strokes in a race of 200 m freestyle are analyzed. The hydrodynamic forces acting on the hands of the top swimmers are computed, and the comparison of two swimmers shows that the stroke of the faster swimmer, who advanced at 1.84 m/s during the stroke-analysis, generated larger thrust with higher thrust efficiency than that of the slower swimmer, who advanced at 1.75 m/s. The applicability of the present stroke analysis system has been proved through this analysis.
    Full-text · Article · Dec 2013 · Journal of sports science & medicine
Show more