ESE - Publicações em Proceedings Indexadas à WoS/Scopus
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Browsing ESE - Publicações em Proceedings Indexadas à WoS/Scopus by Author "Barbosa, Tiago M."
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- Aerodynamics of a wheelchair sprinter racing at the 100m world record pace by CFDPublication . Forte, Pedro; Marinho, D.A.; Morais, J.E.; Morouço, Pedro; Pascoal-Faria, Paula; Barbosa, Tiago M.The aim of this study was to analyze aerodynamics in a racing position of a wheelchair-racing sprinter, at the world record speed. The athlete and wheelchair were scanned at the beginning of the propulsive phase position (hands near the handrims at 12h) for the 3D model acquisition. Numerical simulation was run on Fluent, having as output the pressure, viscosity and total drag force, and respective coefficients of drag at the world record speed in T-52 category. Total drag was 7.56N and coefficient of drag was 1.65. This work helped on getting a deeper insight about the aerodynamic profile of a wheelchair-racing athlete, at a 100m world record speed.
- Analysis of the aerodynamics by experimental testing of an elite wheelchair sprinterPublication . Barbosa, Tiago M.; Forte, Pedro; Morais, J.E.; Coelho, EduardaThe aim was to compare the resistive forces acting upon an European wheelchair medallist. The coast-down technique was selected to estimate the resistance in the upright position and racing positions with the neck in hyperextension and flexion, respectively. In the upright position, racing position with the neck in flexion and hyperextension the effective surface area was 0.1747, 0.1482 and 0.1456m2, respectively. The coefficient of rolling friction was 0.00119, 0.00489, 0.00618 and the power to overcome drag 26.62, 22.59, 22.19W for the same positions. As a conclusion, the resistance acting upon the sprinter is different according to his position on the chair. Slight changes in the head position over the race can affect by almost 2% the power output.
- Comparison of the World and European Records in the 100m Dash by a Quasi-Physical ModelPublication . Barbosa, Tiago M.; Forte, Pedro; Marinho, D.A.; Reis, Victor M.The aim was to employ a quasi-physical model to analyse the performance and biomechanics of the World and European records at the 100m dash in Athletics. At the time of this research, the World record was hold by Usain Bolt (Jamaica) with 9.58s and the European record 9.86s by Francis Obikwelu (Portugal). The analysis of the performance employs a quasi-physical model that feature the drive, maintenance, velocity and drag terms. Obikwelu showed a slower start (drive term) and Bolt a lower rate of deceleration over the race (propulsive term). The velocity and drag terms were higher for Bolt. Correcting the race time for a hypothetical null wind speed, Bolt´s time would have been 9.62s (i.e. a 0.04s impairment) and 9.89s for Obikwelu (i.e. a 0.03s impairment).
- Is front crawl swimming performance affected by hydrodynamic drag in young swimmers?Publication . Silva, A.J.; Marques, Mário C.; Garrido, Nuno D.; Barbosa, Tiago M.; Costa, M.J.; Louro, Hugo; Reis, Victor M.; Marinho, D.A.Swimming performance is affected by several factors including the hydrodynamic drag. Hydrodynamic drag is the force that a swimmer has to overcome in order to maintain his movement through water and is highly dependent on swimming technique. PURPOSE: To analyse in young swimmers the relationship between hydrodynamic drag and the front crawl performance. METHODS: 25 young swimmers (11 females and 14 males) participated in this study. Their mean (standard deviation) age, body mass, height and best swimming performance in 100 m front crawl was 12.08 (0.76) years, 43.08 (7.60) kg, 1.52 (0.08) m and, 75.11 (9.57) s, respectively
- The changes in fractal dimension after a maximal exertion in swimmingPublication . Barbosa, Tiago M.; Chen, Simin; Forte, Pedro; Morais, J.E.Quite often linear variables are not sensitive enough to explain the changes in the motor behavior of elite athletes. So, non-linear variables should be selected. The aim was to compare the fractal dimension before and after a maximal bout swimming front-crawl. Twenty-four subjects performed an all-out 100m trial swimming front-crawl. Immediately before (Pre-test) and after the trial (Post-test) a speed-meter cable was attached to the swimmer’s waist to measure the hip speed from which fractal dimension was derived. The fractal dimension showed a significant decrease with a moderate effect size between pre- and post-tests. Twenty-one out of 24 swimmers decreased the fractal dimension. As a conclusion, there is a decrease in the fractal dimension and hence in the swimming behavior complexity being under fatigue after a maximal trial.
- The effect of depth on drag during the gliding phase in swimmingPublication . Marinho, D.A.; Ribeiro, João; Mantripragada, Narendra; Machado, Leandro; Vilas-Boas, João Paulo; Fernandes, Ricardo J.; Barbosa, Tiago M.; Rouboa, Abel; Silva, A.J.The gliding phase following a swimming start or turn is an important component of the overall swimming performance. PURPOSE: To analyse the effect of depth on hydrodynamic drag force during the underwater gliding, using computational fluid dynamics. METHODS: A three-dimensional domain was created to simulate the fluid flow around a swimmer model, representing the geometry of part of a lane in a swimming pool. The water depth of this domain was 1.50 m with a 3.0 m width and 11.0 m length. Computational fluid dynamics methodology was used to perform numerical simulations in the created domain which was divided into a number of mesh cells. The k-epsilon turbulent model was applied to the flow around a three-dimensional model of a male adult swimmer in a prone gliding position with the arms extended at the front. General moving object model was used to simulating the body as the displacing object. During the gliding, the swimmer model’s middle line was placed at three different water depths: at 0.20 m (just under the surface), at 0.75 m (middle of the pool), and at 1.30 m (bottom of the pool). The drag coefficient and the hydrodynamic drag force were computed using a steady velocity of 2.50 m/s for the different depths run for 3 s in each case. RESULTS: The drag coefficient was 0.37, 0.34 and 0.30 and the drag force was 141.40 N, 128.10 N and 115.30 N when gliding at a water depth of 0.20 m, 0.75 m and 1.30 m, respectively, at the time of 2 s when the swimmer was approximately at the middle of the computational pool. CONCLUSIONS: The hydrodynamic drag values for the gliding decreased with the increase in depth. This decrease of drag values with depth can be due to the reduction of the wave drag effect, which has an important contribution to total drag near the water surface. Reducing the drag experienced by swimmers during the glide off the wall can decrease start and turn times and unnecessary energy loss. Hence, these results suggested that gliding at 0.75 m under the water surface or deeper seemed to be an optimal gliding depth for minimizing drag and improve swimming performance