Resistance and flow field of a submarine in a density stratified fluid

The research on resistance and wake of an underwater submarine in density-stratified fluid is very necessary. To study the hydrodynamic performances of an underwater submarine navigating in density-stratified fluid, a CFD model is established based on RANS equations, combined with the Realizable k - ε turbulence and Euler multiphase flow models. Meanwhile, the VOF method is used for capturing the interface. At first, the established CFD model is validated by comparing with experimental results. Thereafter, the resistance and flow field of a full-scale SUBOFF model in density-stratified and uniform fluids with different forward speeds, submerged positions and fluid densities are investigated. The results show that the forward speed and submerged depth significantly affect the hydrodynamic performances of the submarine. However, the density of the lower layer and the distance of submarine above the internal surface both have little effect. The influence of the density stratification on the resistance increases as the forward speed becomes faster and the position becomes closer to the free surface. The pattern of the internal wave when submarine navigates under the internal interface is obviously different from that when submarine navigates above the internal interface. In general, the pattern of the internal wave changes more slowly than that of the free surface.