Numerical Investigation of Swimmer’s Gliding Stage with 6-DOF Movement

Abstract

The purpose of this study is to analyze the motion status of swimmers during their gliding stage using a numerical simulation method. This simulation strategy is conducted by solving the 3D incompressible Navier-Stokes equations using the Realizable k-ε turbulence closure equations in combination with the Six Degrees of Freedom (6-DOF) method. The uneven mass distribution of a swimmer and the roughness of the surface of the body are taken into consideration. The hydrodynamic characteristics and movement characteristics of the swimmers at different launch speeds were analyzed. The calculated results suggest that an optimal instant for starting propulsive movement is when the velocity of the swimmer decreases by 1.75 m/s to 2.0 m/s from an initial horizontal velocity of 3.1 m/s to 3.5 m/s.

The Transition from Underwater to Surface Swimming During the Push-off Start in Competitive Swimmers

“…On the other hand, they were similar to those presented by Seifert et al (2004) in crawl (1.61 m/s), Chollet et al (2008) in backstroke (1.34 m/s) and Chollet et al (2006) and Seifert et al (2007) in butterfly (1.47 m/s), although these authors considered transition to the end of the first stroke cycle. Interestingly, backstroke was the slowest stroke compared to other studies (Chollet et al, 2008;Navandar et al, 2016) which could be related to a greater time and distance from the push off to the end of the underwater kicking or to an excessive early beginning of the kicking action after gliding (Li et al, 2017). It should also be noted that the underwater trajectory and depth (Naemi and Sanders, 2008;Vantorre et al, 2010a, b, c) could affect the subsequent transition to surface as, if inadequately performed, it could slow down swimmers before the stroking resumption.…”

“…It should not be forgotten that there is a strong relationship between total passive drag force and the resistance coefficient measured by computational fluid dynamics (CFD) according to Barbosa et al (2018). Once the swimmer decreases its forward speed to about 1.75 to 2.0 m/s (Li et al, 2017) (from 3-3.5 m/s in which the wall push off is performed) then he/she must finalize the gliding phase and begin with the underwater propulsion phase, in order to reduce the swimmer's Journal of Human Kinetics -volume 72/2020 http://www.johk.pl deceleration (Naemi and Sanders, 2008;Takeda et al, 2009;Vantorre et al, 2010a, b, c). In the underwater propulsion phase, swimmers move their feet simultaneously vertically (Von Loebbecke et al, 2009), in a wave motion (Connaboy et al, 2009).…”

A study on the hydrodynamic performance of manta ray biomimetic glider under unconstrained six-DOF motion

“…Compared to the dynamic mesh method we used in the past work [ 22 ], the MBZMU method can greatly reduce the number of computational grids. Fig 2 shows the division of computational domain and grids generated by ANSYS Gambit.…”

“…Experimental results show that the glider climbs continuously to the water surface, and the deflection angle increases continuously at the same time. We have investigated the gliding stage of human swimmers in previous work to verify the rationality of the traditional optimal instant to initiate underwater leg propulsion [ 22 ]. Similar experiments were carried out, and the swimmer model is found to glide almost straight with a small pitch degree [ 22 ].…”

“…We have investigated the gliding stage of human swimmers in previous work to verify the rationality of the traditional optimal instant to initiate underwater leg propulsion [ 22 ]. Similar experiments were carried out, and the swimmer model is found to glide almost straight with a small pitch degree [ 22 ]. It is noted that the density of the model is higher than that of water, so the reason why the model glides nose-up to the surface of the water is not due to the single factor of buoyancy.…”