Experimental Study of the Drag and Wave-Induced Surge Forces on an Underwater Vehicle Operating Near the Surface

Abstract

Abstract This paper investigates the steady drag and oscillating wave-induced surge forces on an underwater vehicle caused by near surface operations. We experimentally measured the longitudinal forces on a submerged body with forward speed subject to single regular waves of various lengths. A circular cylinder body with hemispheric end caps was tested in a towing tank with wavemaking capability. Since the drag force is driven by viscous effects and flow separation, and to confirm if either of these affect the surge forces, we also tested the body with flat end faces to force flow separation at the leading edges. Our results show an increase in the calm water component of the drag force for the flat end face geometry and that both end shapes experience an increasing nonlinear wave-induced component of drag as wavelength increases. For the wave-induced surge forces, we observed that viscous effects and forward speed both play, at most, minor rolls as there was no significant difference between the surge forces on the two different end shapes or between stationary bodies and ones with forward speed.