Submarine Maneuvers Using Direct Overset Simulation of Appendages and Propeller and Coupled CFD/Potential Flow Propeller Solver

This article presents two approaches to simulate maneuvers of a model radio-controlled submarine. In the direct simulation approach, rudders, stern planes, and propellers are gridded and treated as moving objects using dynamic overset technology. The second approach couples the overset computational fluid dynamics (CFD) solver and a potential flow propeller code, with both codes exchanging velocities at the propeller plane and wake, body forces, and propeller forces and moments, whereas rudders and stern planes are still explicitly resolved. It is shown that during the maneuvers, the range of advance coefficients does not deviate much from the design point, making a coupled approach a valid choice for standard maneuvering simulations. By allowing time steps about an order of magnitude larger than for the direct simulation approach, the coupled approach can run about five times faster. The drawback is a loss of resolution in the wake as the direct propeller simulation can resolve blade vortical structures. Open water propeller curves were simulated with both the direct propeller approach and the coupled approach, showing that the coupled approach can match the direct approach performance curves for a wide range of advance coefficients. Simulations of a horizontal overshoot maneuver at two approach speeds were performed, as well as vertical overshoot and controlled turn maneuvers at high speed. Results show that both CFD approaches can reproduce the experimental results for all parameters, with errors typically within 10%.