Browsing by Author "Morais, J.E."
Now showing 1 - 10 of 166
Results Per Page
Sort Options
- Aerodynamic analysis of human walking, running and sprinting by numerical simulationsPublication . Forte, Pedro; Sousa, Nuno; Teixeira, José Eduardo; Marinho, D.A.; Monteiro, A.M.; Bragada, José A.; Morais, J.E.; Barbosa, Tiago M.The drag in walking, running, and sprinting locomotion can be assessed by analytical procedures and experimental techniques. However, assessing the drag variations by these three main locomotion’s (i.e., walking, running, and sprinting) were not found using computational fluid dynamics. (CFD). Thus, the aim of this study was two-fold: (1) to assess the aerodynamics of human walking, running, and sprinting by CFD technique; 2) compare such aerodynamic characteristics between walking and running. Three 3D models were produced depicting the walking, running, and sprinting locomotion techniques, converted to computer aided design models and meshed. The drag varied with 4 locomotion type. Walking had the lowest drag, followed-up by running and then sprinting. At the same velocities, the drag was larger in walking than in running and increased with velocity. In conclusion, drag varied with locomotion type. Walking had the lowest drag, followed-up by running and then sprinting. At the same velocities, the drag was larger in walking than in running and increased with velocity.
- 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.
- Agreement between different methods to measure the active drag coefficient in front-crawl swimmingPublication . Morais, J.E.; Barbosa, Tiago M.; Garrido, Nuno D.; Cirilo-Sousa, Maria S.; Silva, A.J.; Marinho, D.A.The aim of this study was to analyze the agreement of the active drag coefficient measured through drag and propulsion methods. The sample was composed of 18 swimmers (nine boys: 15.9 ± 0.9 years; nine girls: 15.3 ± 1.2 years) recruited from a national swimming team. The velocity perturbation method was used as the drag measurement system and the Aquanex system as the propulsion system. For both sexes combined, the frontal surface area was 0.1128 ± 0.016 m2, swim velocity 1.54 ± 0.13 m∙s-1, active drag 62.81 ± 11.37 N, propulsion 68.81 ± 12.41 N. The level of the active drag coefficient agreement was calculated based on the mean values comparison, simple linear regression, and Bland Altman plots. The mean data comparison revealed non-significant differences (p > 0.05) between methods to measure the active drag coefficient. Both the linear regression (R2 = 0.82, p < 0.001) and Bland Altman plots revealed a very high agreement. The active drag coefficient should be the main outcome used in the interpretation of the swimmers’ hydrodynamic profile, because it is less sensitive to swimming velocity. Coaches and researchers should be aware that the active drag coefficient can also be calculated based on propulsion methods and not just based on drag methods. Thus, the swimming community can now use different equipment to measure the hydrodynamics of their swimmers
- Análise da magnitude das assimetrias posturais em crianças e jovens futebolistasPublication . Forte, Pedro; Morais, J.E.; Barbosa, Tiago M.; Reis, AntónioPostural asymmetries are related with different types of injuries. Upon that, postural control may predict further problems as pain events or muscular ruptures. Moreover, sports specific tasks may increase muscular hypersolicitation and develop strength asymmetries. Thus, sports practice such as soccer may explain some postural asymmetries.
- Análise de variáveis preditivas do deslize aquatic através de um modelo de path-analysisPublication . Morais, J.E.; Costa, M.J.; Jesus, Sérgio; Moreira, Marc; Feitosa, Wellington G.; Silva, A.J.; Marinho, D.A.; Barbosa, Tiago M.A velocidade de nado depende da propulsão e arrasto hidrodinâmico. Para um nadador se deslocar no meio aquático tem de produzir a mesma quantidade de propulsão e arrasto hidrodinâmico (Barbosa et al., 2010)
- Análise do desempenho individual de jovens basquetebolistas ao longo de um jogo de apuramento ao campeonato nacional de basquetebolPublication . Teixeira, José Eduardo; Bessa, Rui; Morais, J.E.; Monteiro, A.M.; Forte, PedroA análise desportiva em basquetebol tem suscitado um crescente interesse por parte dos quadros técnicos. A análise estatística dos scores individuais permite avaliar a probabilidade de sucesso para as diferentes estratégias ofensivas e defensivas, identificando os fatores que condicionam a performance coletiva. O objetivo deste estudo foi comparar os scores individuais das duas equipas nos diferentes períodos do jogo.
- Análise do desempenho individual de jovens basquetebolistas ao longo de um jogo de apuramento ao campeonato nacional de basquetebol.Publication . Teixeira, José Eduardo; Bessa, Rui; Morais, J.E.; Monteiro, A.M.; Forte, PedroA análise desportiva em basquetebol tem suscitado um crescente interesse por parte dos quadros técnicos. A análise estatística dos scores individuais permite avaliar a probabilidade de sucesso para as diferentes estratégias ofensivas e defensivas, identificando os fatores que condicionam a performance coletiva. O objetivo deste estudo foi comparar os scores individuais das duas equipas nos diferentes períodos do jogo.
- Analysis of a normal and aero helmet on an elite cyclist in the dropped positionPublication . Forte, Pedro; Marinho, D.A.; Barbosa, Tiago M.; Morais, J.E.Cyclists use to wear different helmets and adopt different body positions on the bicycle to minimize resistance. The aim of this study was to compare a standard helmet with the new aero road helmets in a bicycle-cyclist system by CFD on the dropped position. An elite level road cyclist volunteered to this research. The cyclist was scanned on his racing bicycle on the dropped position wearing competition gear and a standard helmet and an aero road helmet. A three-dimensional domain around the cyclist with 7 m of length, 2.5 m of width and 2.5 m of height and meshed with more than 43 million of prismatic and tetrahedral elements. The numerical simulations were conducted at 11.11 m/s. The numerical simulations outputs were viscous, pressure and total drag and coefficient of drag. The standard helmet presented a viscous drag of 10.52 N, a pressure drag of 16.51 N and a total drag of 21.98 N. The aero road helmet presented a pressure drag of 7.40 N, a viscous drag of 12.56 N and a total drag of 19.96 N. Moreover, the aero road helmet presented a lower viscous, pressure and total drag coefficient in comparison to the standard helmet. It is possible to conclude that an aero road helmet imposes less drag in comparison to a standard helmet.
- Analysis of cyclist’s drag on the aero position using numerical simulations and analytical procedures: a case studyPublication . Forte, Pedro; Marinho, D.A.; Nikolaidis, Pantelis Theo; Knechtle, Beat; Barbosa, Tiago M.; Morais, J.E.Resistance acting on a cyclist is a major concern among the cycling fraternity. Most of the testing methods require previous training or expensive equipment and time-consuming set-ups. By contrast, analytical procedures are more affordable and numerical simulations are perfect for manipulating and controlling inputs. The aim of this case study was to compare the drag of a cyclist in the aero position as measured using numerical simulation and analytical procedures. METHODS: An elite male cyclist (65 kg in mass and 1.72 m in height) volunteered to take part in this research. The cyclist was wearing his competition gear, helmet and bicycle. A three-dimensional model of the bicycle and cyclist in the aero position was obtained to run the numerical simulations. Computational fluid dynamics (CFD) and a set of analytical procedures were carried out to assess drag, frontal area and drag coefficient, between 1 m/s and 22 m/s, with increments of 1 m/s. The t-test paired samples and linear regression were selected to compare, correlate and assess the methods agreement. RESULTS: No significant differences (t = 2.826; p = 0.275) between CFD and analytical procedures were found. The linear regression showed a very high adjustment for drag (R2 = 0.995; p < 0.001). However, the drag values obtained by the analytical procedures seemed to be overestimated, even though without effect (d = 0.11). CONCLUSIONS: These findings suggest that drag might be assessed using both a set of analytical procedures and CFD
- Analysis of the aerodynamics by experimental testing of an elite wheelchair sprinterPublication . Barbosa, Tiago M.; Forte, Pedro; Morais, J.E.; Coelho, EduardaOne concern for wheelchair sprinters is the head’s alignment racing. This misalignment may increase significantly the resistance acting upon the athlete albeit, evidence on this is scarce in wheelchair racing. A feasible way to gather insight on the effects of misalignments in the aerodynamics is the cost-down technique.