3-D Computational FluidDynamics of the Hand and Forearm in Swimming

Abstract

The creation of propulsive force in human swimming has been studied recently using numerical simulation techniques with computational fluid dynamics (CFD) models. Some limitations, however, still persist, regarding the geometrical representation of the human limbs. PURPOSE: To determine the propulsive force in a hand/forearm segment 3-D model using CFD. METHODS: A Fluent© code designed 3-D model of the hand/forearm and a domain with a 3-D mesh for the simulation of the water flow around the model were created. The whole domain was meshed with 400.000 trapezoidal elements of 4 nodes each. Numerical simulations for the whole computational steady domain were calculated in the 3 dimensions. Models used in the simulations were created in CAD, based on realistic dimensions of a right adult human hand/forearm. The governing system of equations considered was the incompressible Reynolds averaged Navier-Stokes equations with the standard k-epsilon model. Flow velocities were chosen to be within or near the range of typical hand velocities during freestyle swimming underwater path: from 0.5 m.s-1 to 4 m.s-1. Angles of attack of hand/forearm model of 0°, 45° e 90°, with a angle of orientation of 0° (thumb as the leading edge) were used for the calculations. The measured forces on the hand/forearm model were decomposed into drag and lift components. The combined hand and forearm drag (Cd) and lift (C1) coefficients were considered. RESULTS: The magnitude of Cd and Cl remained constant throughout the flow velocities tested. Angles of attack of 0°, 45° and 90° produced, respectively, Cd values of 0.35, 0.63 and 1.1 and Cl values of 0.18, 0.32 and 0.05. CONCLUSIONS: Cd was the main contributor for propulsion, with a maximum of force production corresponding to an angle of attack of 90°, as expected. Cl has a residual influence in the generation of propulsive force by the hand/forearm segment at angles of attack of 0° and 90°, but it is important with an angle of attack of 45°. These data confirm experimental studies reporting reduced contribution of lift component to the overall propulsive force generation by the hand/forearm in front crawl swimming, except for the insweep phase, when the angle of attack nears 45°.