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- A Comparison of Experimental and Analytical Procedures to Measure Passive Drag in Human SwimmingPublication . Barbosa, Tiago M.; Morais, Jorge; Forte, Pedro; Neiva, Henrique; Garrido, Nuno; Marinho, DanielThe aim of this study was to compare the swimming hydrodynamics assessed with experimental and analytical procedures, as well as, to learn about the relative contributions of the friction drag and pressure drag to total passive drag. Sixty young talented swimmers (30 boys and 30 girls with 13.59±0.77 and 12.61±0.07 years-old, respectively) were assessed. Passive drag was assessed with inverse dynamics of the gliding decay speed. The theoretical modeling included a set of analytical procedures based on naval architecture adapted to human swimming. Linear regression models between experimental and analytical procedures showed a high correlation for both passive drag (Dp = 0.777*Df+pr; R2 = 0.90; R2a = 0.90; SEE = 8.528; P<0.001) and passive drag coefficient (CDp = 1.918*CDf+pr; R2 = 0.96; R2a = 0.96; SEE = 0.029; P<0.001). On average the difference between methods was -7.002N (95%CI: -40.480; 26.475) for the passive drag and 0.127 (95%CI: 0.007; 0.247) for the passive drag coefficient. The partial contribution of friction drag and pressure drag to total passive drag was 14.12±9.33% and 85.88±9.33%, respectively. As a conclusion, there is a strong relationship between the passive drag and passive drag coefficient assessed with experimental and analytical procedures. The analytical method is a novel, feasible and valid way to gather insight about one's passive drag during training and competition. Analytical methods can be selected not only to perform race analysis during official competitions but also to monitor the swimmer's status on regular basis during training sessions without disrupting or time-consuming procedures.
- The variations on the aerodynamics of a world-ranked wheelchair sprinter in the key-moments of the stroke cyclePublication . Forte, Pedro; Marinho, Daniel; Morais, Jorge; Morouço, Pedro; Barbosa, Tiago M.Biomechanics plays an important role helping Paralympic sprinters to excel, having the aerodynamic drag a significant impact on the athlete's performance. The aim of this study was to assess the aerodynamics in different key-moments of the stroke cycle by Computational Fluid Dynamics. A world-ranked wheelchair sprinter was scanned on the racing wheelchair wearing his competition gear and helmet. The sprinter was scanned in three different positions: (i) catch (hands in the 12h position on the hand-rim); (ii) the release (hands in the 18h position on the hand-rim) and; (iii) recovery phase (hands do not touch the hand-rim and are hyperextended backwards). The simulations were performed at 2.0, 3.5, 5.0 and 6.5 m/s. The mean viscous and pressure drag components, total drag force and effective area were retrieved after running the numerical simulations. The viscous drag ranged from 3.35 N to 2.94 N, pressure drag from 0.38 N to 5.51 N, total drag force from 0.72 N to 8.45 N and effective area from 0.24 to 0.41 m2. The results pointed out that the sprinter was submitted to less drag in the recovery phase, and higher drag in the catch. These findings suggest the importance of keeping an adequate body alignment to avoid an increase in the drag force.
- The assessment of a world-ranked wheelchair sprinter aerodynamics analysis by computer fluid dynamicsPublication . Forte, Pedro Miguel Gomes; Marinho, Daniel Almeida; Barbosa, Tiago Manuel Cabral dos SantosAerodynamics can play an important role in the performance of a wheelchair spinter. The aim of this thesis was to analyse the aerodynamics of a wheelchair sprinter by computer fluid dynamics. This thesis comprises a series of four studies (a review of the literature and three empirical studies). The studies aimed to: (i) review the literature on aerodynamics in wheelchair racing; (ii) compare two different helmets (road vs time trial) at several speeds and head positions by CFD. (iii) assess the aerodynamics in different key-moments of the stroke cycle by CFD; (iv) compare the mechanical power and energy cost of transportation delivered by an elite wheelchair sprinter in key-moments of the stroke cycle. The main conclusions were: (i) there is a lack of research on wheelchair racing aerodynamic’s assess by CFD; (ii) a time trial helmet imposed lower drag keeping a neck hyperextension; (iii) the aerodynamics of a wheelchair racing athlete varied over the different phases of the stroke cycle; (iv) the mechanical power and energy cost in elite wheelchair racing varied in different phases of the stroke cycle. The main conclusion of this thesis was that it is possible to enhance the aerodynamics of a wheelchair sprinter by selecting the best sport garement and equipment, as well as keeping a good body alignment in the key-phases of the stroke cycle.