Investigation of Step Sweep-Forward Angle Effects on the Hydrodynamic Performance of a Planing hull

One of the most effective methods to diminish the drag of the planning craft is using step at the bottom of the hull. Stepped hull causes to reduce the wet area and as a results reduce the drag. Shape of the step may be designed in a straight line through the entire width of the hull or it may be V-shape with a forward or backward sweep angle. In this paper, the effect of step sweep-forward angle on the hydrodynamic performance of a planning chine hull vessel is investigated by finite volume method. Reynolds-Averaged Navier-Stokes equations with standard k-ɛ turbulence model coupled with volume of fluid equations are solved in order to simulate transient turbulent surface flow around the hull with the help of Ansys CFX software. In order to predict the craft motions, equations of rigid body motions for two degrees of freedom are coupled with fluid flow governing equations. To validate presented numerical model, first the numerical results are compared with available experimental data and then obtained numerical results at different speeds and step angles are presented and discussed. The results show that the sweep-forward step angle up to 10 degrees have an insignificant effect on dynamic trim and sinkage, but its effect on the reduction of drag is significant.