Numerical study of a novel small waterplane area USV advancing in calm water and in waves using the higher-order Rankine source method

The wave loads and motion responses of an Unmanned Surface Vehicle (USV) in water will directly influence the powering requirement, energy supply design and function of the installed sensors. In the present article, to investigate the wave loads and motions response characteristics of a USV advancing on the free surface, a Higher-Order Rankine Source (HORS) method is proposed. During the discretization of the boundary elements, bi-quadratic B-splines are applied to distribute the velocity potentials on the body surface and free surface. Based on the proposed HORS method, steady state simulation and time-domain simulation approaches are both used for predicting the wave loads and motion responses of a novel Small Waterplane Area (SWA) USV in calm water and regular waves, respectively. The predicted wave loads in calm water and the predicted heave and pitch in heading wave are compared with corresponding model test data. The good agreement found indicates the validity of the proposed HORS method. Finally, the heave and pitch motion responses and the wave components of the USV including diffraction and radiation forces and Froude-Krylov forces are investigated when the SWA USV is running against heading wave under different conditions of wavelength, wave steepness and advancing velocity.