COUPLING A HIGH FIDELITY NEAR SURFACE EFFECTS MODEL INTO PARAMARINE S4

Abstract

When a submarine is operating at depths typical of those required when using the periscope, snorting during the period of recharging the batteries or, in some cases, at slow to zero speed whilst hovering, the submarine can experience complex oscillatory motion due to higher order sea loads. The second order vertical plane loads can manifest themselves as a mean and time varying suction force effectively causing the submarine to be drawn to the surface risking broaching and increasing the possibility of detection. Current methodologies for modelling near surface effects tend to utilize coefficientbased methods to represent the first and second order wave forces on a submarine body. These empirical methods may be suitable for some applications but are not able to capture all the effects of the submarine operating close to the free surface. As the body approaches the free surface, the flow field around the submarine is modified by the gravitational wave effects, changing the pressure distribution across the body and hence the forces and moments. This change in force is dependent upon the shape of the body and the environment and, therefore, it is impractical that a coefficients-based approach could cover all these scenarios to any great level of fidelity. This paper presents a potential flow method for quantifying the hydrodynamic loads on a fully appended submarine when in proximity and under the influence of surface waves. The paper presents some validation of the method and describes its integration with the Paramarine S4 submarine manoeuvring software.