In this study drag and liftforces were measured on two models of a human hand and forearm towed in a towing tank. To compare the results of models with different size at different velocities force data were normalized to drag and lift coefficients (Cd and Cl). Influence of the orientation ofthe model with respect to the flow, velocity, size of the model and the relative contribution of the hand and forearm on Cd and Cl were studied. The orientation of the model with respect to the line of motion was varied by rotating the model around three axes andquantified using the angle of pitch (AP; the angle between the hand plane and the flow), and the sweep back angle (SB; the orientation of the flow vector when projected on the hand plane). Cd was maximal when the palm of the hand is almost perpendicular to the flow (AP = 65 degrees, SB = 342 degrees). Cl shows maximal values at two different orientations: with the hand in a thumb leading position, AP = 31 degrees, SB = 358 degrees, and with the hand in a little finger-leading position, AP = 48 degrees, SB = 193 degrees. The orientation of the hand was very critical in generating lift forces. By contrast, the influence of velocity and size of the model on Cd and Cl was limited. The relative contribution of the hand and forearm on Cd and Cl was examined by varying the immersion depth of the model. In the experiments where only the hand was towed, Cd was about the same as for the condition where hand and forearm together were towed. Cl reached the highest values in the experiments where only the hand was towed. The hands are the main contributors for the generation of lift force.
© Copyright 1995 Journal of Biomechanics. Elsevier. All rights reserved.