The Effect of Depth on Drag During the Streamlined Glide: A Three-Dimensional CFD Analysis

Abstract

The aim of this study was to analyze the effects of depth on drag during the streamlined glide in swimming using Computational Fluid Dynamics. The Computation Fluid Dynamic analysis consisted of using a three-dimensional mesh of cells that simulates the flow around the considered domain. We used the K-epsilon turbulent model implemented in the commercial code Fluent® and applied it to the flow around a three-dimensional model of an Olympic swimmer. The swimmer was modeled as if he were gliding underwater in a streamlined prone position, with hands overlapping, head between the extended arms, feet together and plantar flexed. Steady-state computational fluid dynamics analyses were performed using the Fluent® code and the drag coefficient and the drag force was calculated for velocities ranging from 1.5 to 2.5 m/s, in increments of 0.50m/s, which represents the velocity range used by club to elite level swimmers during the push-off and glide following a turn. The swimmer model middle line was placed at different water depths between 0 and 1.0 m underwater, in 0.25m increments. Hydrodynamic drag decreased with depth, although after 0.75m values remained almost constant. Water depth seems to have a positive effect on reducing hydrodynamic drag during the gliding. Although increasing depth position could contribute to decrease hydrodynamic drag, this reduction seems to be lower with depth, especially after 0.75 m depth, thus suggesting that possibly performing the underwater gliding more than 0.75 m depth could not be to the benefit of the swimmer.

The effect of finger spreading on drag of the hand in human swimming

“…The significance of optimal finger spreading can be roughly quantified in terms of swimming time. A swimmer can reach a speed of v s = 2 m/s in front crawl swimming and experiences a drag force of F D = 100 N [25,33,29,16]. Assume that the stroke frequency of a complete cycle is 0.5 s −1 (propulsive phase of one arm takes 1 s) and the backward (slip) velocity of the hand with respect to the water is v h = 2.2 m/s [2,20,7,4].…”

Individual–Environment Interactions in Swimming: The Smallest Unit for Analysing the Emergence of Coordination Dynamics in Performance?

“…By modifying disk orientation and flow characteristics (constant or variable acceleration), they found that hand acceleration (from 2.84 to 5.84 m/s) strongly increased propulsive drag by up to 40%. Following this study, interest turned to evaluating water resistances during glide periods [54,[66][67][68][69]. Investigators scanned the swimmer's whole body and tested resistances as a function of position (arms extended at the front or along the body) and depth.…”

“…Investigators scanned the swimmer's whole body and tested resistances as a function of position (arms extended at the front or along the body) and depth. It appeared that passive drag decreased when depth increased: water drag is maximum at 0.25 m depth, and minimal around 0.75 m depth [68]. Thus, it became clear that swimmers' actions induce different fluid behaviours and that therefore fluid behaviours and swimmer actions need to be considered as an interactive dynamical system [7,9,10].…”

Análisis cinemático de la salida con empuje en nadadores competitivos de nivel nacional

“…Por otro lado, el nado subacuático también se caracteriza por no tener un desplazamiento rectilíneo y a la misma profundidad durante la fase del deslizamiento y la propulsión subacuática, según la división que hicieron Elipot et al (2010b Novais et al (2012) contrastaron dichas afirmaciones, ya que en su estudio la velocidad inicial tras el impulso y la resistencia hidrodinámica podrían condicionar el rendimiento del deslizamiento y de la fase subacuática. Por consiguiente, si el nadador consiguiese minimizar tal resistencia, posiblemente mejorarían los resultados que el simple hecho de aumentar el esfuerzo durante el impulso no incrementando el coste metabólico (Lyttle et al, 1998).…”

“…Aun así, hay autores que también señalan que una inadecuada profundidad o mala trayectoria (Vennell, Pease y Wilson, 2006;Novais et al, 2012) tras la entrada en el agua después de la salida o un mal impulso después de la trayectoria del viraje, podrían incrementar la resistencia y ralentizando al nadador (Blanksby, Gathercole y Marshall, 1996;Lyttle et al, 1998;Lyttle y Benjanuvatra, 2005;Sanders y ByattSmith, 2001), acortando así la distancia del deslizamiento.…”