Wake of a cruciform appendage on a generic submarine at 10$$^\circ $$ yaw

Abstract

The present model geometry is a recent iteration of the Joubert (Defence Science and Technology, Tech. Rep. TR-1920, 2006) generic conventional submarine design and is known as the “BB2”. Wind-tunnel testing of the model at 10 $$^\circ $$ yaw, by China-clay visualisation and by ensemble-averaged measurements using high-resolution stereoscopic particle image velocimetry, shows a similar wake flow at the model-length Reynolds numbers $$Re_\mathrm{L} = 4 \times 10^6$$ and $$8 \times 10^6$$ . The most significant flow feature is on the model upper hull. It is a system of three co-rotating vortices produced by a cruciform appendage which consists of a vertical fin (or sail in American terminology) and two horizontal hydroplanes. Circulation is strongest from the fin tip followed by the windward hydroplane, then the leeward hydroplane. Vortex tracking shows a down-wash of the fin-tip vortex, where the wind-ward- and lee-ward-hydroplane vortices spiral in the rotation direction of the fin-tip vortex. The interpreted flow includes a U-shaped vortex line around the leeward hydroplane, where this vortex line connects the fin-tip vortex and a surface vortex on the leeward side of the fin.