The effect of swimmer's hand/forearm acceleration on propulsive forces generation using computational fluid dynamics

Propulsive forces generated by swimmers hand/forearm, have been studied through experimental tests. However, there are serious doubts as to whether forces quantified in this way are accurate enough to be meaningful. In order to solve some experimental problems, some numerical techniques have been proposed using Computational Fluid Dynamics (CFD). The main purpose of the present work was threefold. First, disseminate the use of CFD as a new tool in swimming research. Second, apply the CFD method in the calculation of drag and lift coefficients resulting from the numerical resolution equations of the flow around the swimmers hand/forearm using the steady flow conditions. Third, evaluate the effect of hand/forearm acceleration on drag and lift coefficients. For these purposes three, two-dimensional (2D), models of a right male hand/forearm were studied. A frontal model (theta = 90 degrees, Phi = 90 degrees) and two lateral models, one with the thumb as leading edge (theta = 0 degrees, = 90 degrees), and the other with the small finger as the leading edge (theta = 0 degrees, Phi = 180 degrees). The governing system of equations considered was the incompressible Reynolds averaged Navier-Stokes equations with the standard k-epsilon model. The main results reported that, under the steady-state flow condition, the drag coefficient was the one that contributes more for propulsion, and was almost constant for the whole range of velocities, with a maximum value of 1.16 (Cd = 1.16). This is valid when the orientation of the hand/forearm is plane and the model is perpendicular to the direction of the flow. Under the hand /forearm acceleration condition, the measured values for propulsive forces calculation were approximately 22.5% (54.440 N) higher than the forces produced under the steady flow condition (44.428 N). By the results, pointed out, we can conclude that: (i) CFD can be considered an interesting new approach for hydrodynamic forces calculation on swimming, (ii) the acceleration of hand/forearm provides more propulsion to swimmers, confirming that some unsteady mechanism must be present in swimming propulsion.