Bubble Image Velocimetry Applied to Swimming
The use of scientific results to improve the performance and efficiency of athletes in sports is very common nowadays. In swimming, biomechanical and physiological analysis together with CFD simulations have been very helpful on improving the swimmers' technique. An experimental approach in the swimming fluid dynamics has been less used. One of the reasons is the difficulty to use laboratory techniques in pools or swimmers in the labs. Therefore, we decided to take a non-intrusive PIV technique to a swimming pool using a bubble curtain to analyze the dolphin kick of a swimmer. First, PIV analysis is applied on images of the bubble curtain in a wave flume with monochromatic waves. The experiments in the wave flume confirms that the bubbles are reliable tracers in the fluid for the relative velocities of swimmers in water. Measurements on the dolphin kicking showed the presence of two vortical structures during each kicking cycle. Further analysis confirms that one of these structures helps on the propulsion of the swimmer. Calculations of the pressure and force were made using the velocity fields. More measurements are needed to confirm the validity of the calculations made.