Numerical investigation of step depth effects on hydrodynamic performance of planing hull using dynamic mesh and 2-DOF model

At low speeds, planing hull performs like a displacement one and buoyancy force has the most influence on it, but, when it reaches to enough speed, hydrodynamic lift force equilibrates 50–90 percent of its weight. Planing hull researchers have introduced different methods in order to achieve the highest speed. A desirable planing hull has low weight-to-power ratio and good maneuverability. Several ways have been applied to reduce drag and one of the best strategies is to use step that leads to less wetted surface and more lift power. This work addresses the numerical study of step height effect on hydrodynamic performance of planing hull. A specified form of a monohull was changed to the step one while important geometric parameters such as Deadrise angle, width and length were equal in both of them. In order to simulate hull movements, a comprehensive series of viscous CFD simulations considering free-surface and 2-DOF motion of the hull (heave and pitch) have been performed by application of dynamic mesh. Results have been presented as contours and plots. According to the results, deeper steps provide greater levels of ventilation but, there is a limit in step depth increment because porpoising happens after a specific height.