Experimental and numerical analysis of submarine mast surface wakes

Submarines, due to operational reasons, are required to approach and pierce the surface with vertically mounted masts such as periscopes and snorkels. These masts have the potential to produce large wakes at the surface, which are susceptible to detection by radar, sonar, or visually. This paper describes an experimental and numerical approach used to replicate and analyse the plume profile generated by the submarine mast at typical speeds used by submarines when operating periscopes. The experimental analysis was conducted in the towing tank at the Australian Maritime College using two different length cylinders ranging in diameter Froude numbers from 0.5 – 4.0, corresponding to typical submarine speeds up to 8 knots. The numerical analysis was carried out using a Large Eddy Simulation (LES) model within the computational fluid dynamics (CFD) software OpenFOAM. The first numerical analysis replicated the experimental set up whilst further numerical simulations were conducted varying the mast geometry. It was found that the plume structure is generated from two separate flow regimes from the cylinder, and both the experimental and numerical data showed a good correlation to previously published data. Varying the configuration by using two smaller masts provided a reduction of almost 20% in the plume height at 8 knots, whilst the use of streamlined bodies resulted in a 75% reduction in bow wave height.