A numerical investigation on interaction effects between two underwater vehicles in close proximity

Underwater vehicles operating in close proximity suffer from significant hydrodynamic interactions, especially when there is a prominent vehicle size disparity. To gain profound insights into the physical mechanisms of interaction effects, this paper investigates the hydrodynamic interactions between a submarine model (SUBOFF) and a much smaller Unmanned Underwater Vehicle (UUV) model using the Reynolds Averaged Navier–Stokes (RANS) method. Firstly, the resistance of SUBOFF is predicted for Verification and Validation (V&V) purpose, from which satisfactory numerical accuracies are achieved. Subsequently, hydrodynamic forces and moments on the two vehicles are predicted, considering 60 layouts with different relative vehicle positions. The simulated flow fields indicate that remarkable impacts on the UUV longitudinal force are due to the distinct flow disturbances and shelter effects caused by the submarine sail. In general, the presence of submarine causes considerable flow variations, resulting in notable vertical forces and pitch moments on UUV. The results further suggest that placing the UUV above the SUBOFF middle-body in a limited region is more favorable. Finally, it is found that keeping the UUV pitch angle below 2° is helpful to avoid apparent increases in vertical force and pitch moment on UUV.