Simulating the Blade-Water Interactions of the Sprint Canoe Stroke

Abstract

As a sprint canoe athlete takes a stroke, the flow around their blade governs the transfer of power from the athlete to the water. Gaining a better understanding of this flow can lead to improved equipment design and athlete technique to increase the efficiency of their stroke. A method of modelling the complex motion of the sprint canoe stroke was developed that was able to simulate the transient 2-phase blade-water interactions during the stroke using computational fluid dynamics (CFD). The blade input motion was determined by extrapolating the changing blade position from video analysis of a national team athlete. To simulate the blade motion a rigid inner mesh translated and rotated according to the extrapolated blade path while an outer mesh deformed according to the translation of the inner mesh; allowing for independent motion of the blade throughout the xy-plane. Instabilities associated with the blade piercing a free surface were dealt with by using a piecewise solution. The developed model provided a first look into the complex hydrodynamics of the sprint canoe stroke. Examination of the resultant flow patterns showed the development and shedding of tip and side vortices and the resultant pressure on the blade. Late in the catch, there was an unrealistic drop in the net force on the blade which was attributed to the over-rotation of the blade causing the top two-thirds of the blade to accelerate the near surface water forward. The inclusion of an approximated shaft flexibility showed the ability to improve the net force to more realistic values.