The effect of geometry on the surface waves generated by vertical surface-piercing cylinders with a horizontal velocity

Bluff bodies advancing through a free surface at high Froude numbers create intricate flow patterns worth further investigation. An example of such flows includes a submarine operating near the free surface which generally will have one or more masts piercing the free surface. These have the potential to produce large wakes at the surface. This article describes the numerical analysis used to investigate possible design modifications to reduce the wake profile of a singular cylindrical mast piercing the free surface. The large eddy simulation model carried out in OpenFOAM computational fluid dynamics software was validated against experimental data obtained by the authors using tow tank experiments. The modifications included the use of a double mast system based on the cylindrical mast and truncated NACA0012 sections. All configurations were performed with a mast cross-sectional area corresponding to a typical submarine snorkel across speeds ranging from two to eight knots. The plume size and mast drag were recorded, and the results show that a 30% reduction in wake profile can be obtained using a double mast system at speeds around eight knots, while at the lower speeds the benefit is not as significant.