Contribution Of Form Drag And Skin Friction Drag During The Swimming Gliding

Abstract

In human swimming, the total drag comprises the skin friction drag, form drag and wave drag. The relative contribution of each component to the overall hydrodynamic drag is controversy issue. PURPOSE: To analyse the relative contribution of the skin friction drag and the form drag for the total drag during the gliding, using computational fluid dynamics. METHODS: A 3-D domain was created to simulate the fluid flow around a swimmer model. The numerical simulation analysis consisted of the use of a three-dimensional mesh of cells that simulates the flow around the human body. Computational fluid dynamics methodology uses the finite volume approach, where the equations are integrated over each control volume. The k-epsilon turbulent model was applied to the flow around a three-dimensional model of a male adult swimmer in two gliding positions: in ventral position with the arms extended at the front and in ventral position with the arms aside the trunk. The swimmer model middle line was placed at a water depth of 0.90 m, equidistant from the top and bottom surfaces of the 3-D domain. The coefficient of drag (CD) was computed using a steady flow velocity of 2 m/s for both gliding situations. The CD was decomposed into form and skin friction drag. RESULTS: The position with the arms extended at the front presented a CD value of 0.43 whereas the position with the arms aside the trunk presented a CD value of 0.74. In the position with the arms extended at the front, form drag and skin friction drag represented, approximately, 87% (CD = 0.37) and 13% (CD = 0.06) of the total drag, respectively. In the position with the arms aside the trunk, form drag and skin friction drag represented, approximately, 92% (CD = 0.68) and 8% (CD = 0.06) of the total drag, respectively. CONCLUSIONS: The gliding position with the arms extended at the front produced lower drag coefficients than with the arms placed aside the trunk. Although form drag was dominant, skin friction drag was by no means negligible during the swimming gliding. Supported by FCT (SFRH/BD/25241/2005; POCTI/DES/58872/2004).