Assessment of passive drag in swimming by numerical simulation and analytical procedure

Abstract

The aim was to compare the passive drag-gliding underwater by a numerical simulation and an analytical procedure. An Olympic swimmer was scanned by computer tomography and modelled gliding at a 0.75-m depth in the streamlined position. Steady-state computer fluid dynamics (CFD) analyses were performed on Fluent. A set of analytical procedures was selected concurrently. Friction drag (D), pressure drag (D), total passive drag force (D) and drag coefficient (C) were computed between 1.3 and 2.5 m · s by both techniques. D ranged from 45.44 to 144.06 N with CFD, from 46.03 to 167.06 N with the analytical procedure (differences: from 1.28% to 13.77%). C ranged between 0.698 and 0.622 by CFD, 0.657 and 0.644 by analytical procedures (differences: 0.40-6.30%). Linear regression models showed a very high association for D plotted in absolute values (R = 0.98) and after log-log transformation (R = 0.99). The C also obtained a very high adjustment for both absolute (R = 0.97) and log-log plots (R = 0.97). The bias for the D was 8.37 N and 0.076 N after logarithmic transformation. D represented between 15.97% and 18.82% of the D by the CFD, 14.66% and 16.21% by the analytical procedures. Therefore, despite the bias, analytical procedures offer a feasible way of gathering insight on one's hydrodynamics characteristics.

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

“…The men travelled almost 20 cm longer than women (0.84 ± 0.04 and 0.66 ± 0.04 m), while speed (1.59 ± 0.03 vs. 1.38 ± 0.03 m/s) showed 13.2% faster values in men. These differences according to Vantorre et al (2010a, c), could be related to a greater muscular power of legs or a more hydrodynamic position in men (Barbosa et al, 2018;Houel et al, 2013;Marinho et al, 2011;Von Loebbecke et al, 2009). However, since other research has analyzed the underwater phase without taking into account the transition phase from diving to swimming (Fischer and Kibele, 2016;Vantorre et al, 2010a, b, c), it is impossible to contrast our findings.…”

“…Concerning that phase, the positions of the fully extended arms in the front seem to substantially reduce the negative hydrodynamic effects of the morphology of the human body (Marinho et al, 2011). 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).…”

Quantifying the wave resistance of a swimmer

“…A large body of research has focused on quantifying the passive drag of a swimmer [2]. However, there has been less focus on quantifying the magnitude of wave resistance which contributes to the total passive drag that acts on a swimmer: 1. experimental techniques using a flume or towing swimmers or mannequins [15,1,13], 2. numerical simulations [16], and 3. analytical methods drawing from naval architectural techniques [17,13,14]. Of specific interest 90 is how these methods are employed to investigate the influence of wave resistance on the passive drag of a swimmer.…”

Thrust-versus-endurance trade-off optimization in swimming

“…However, these computationally expensive approaches, at least six orders of magnitude more expensive than Lighthill (Molland and Turnock, 2007) are as yet unvalidated and only presented in a qualitative manner describing the flow field behaviour rather than giving a detailed breakdown of forces. The state-of-the-art in CFD is attempting to compute the forces on a forearm and hand during a front crawl stroke with qualitative agreement with experimental measurements (Samson et al, 2017), whereas progress is being made with validation of passive glide (Banks et al, 2014;Barbosa et al, 2017).…”