Exact evaluation of hydrodynamic loads on ships using NURBS surfaces and acceleration potential

Abstract

The development of an accurate surface intersecting methodology and adaptive acceleration potential scheme, in order to precisely compute pressure on the wet surface of ships hulls, is presented. Non-Uniform Rational B-Spline (NURBS) surfaces are used to describe the ships hulls and the free surface evolutions. The intersection of free surface with ship hull is found by solving the resultant system of equations yielded from surface intersecting scheme. The pressure distribution over the exact wet surface of ship hull surface is obtained based on acceleration potential in a time domain simulation. Hence, implicit body boundary condition is applied to evaluate the time derivative of velocity potential on the hull surface in a fully nonlinear numerical wave tank. On the other hand, tangential derivatives of the velocity potential on the wet surface are approximated by B-Spline surface. Wave propagation is considered to examine the accuracy and convergence of the present solution. Motions of a Wigley hulls in linear wave are compared with experimental measurements and prior numerical solutions to verify the present numerical procedure. Also, fully nonlinear motions of a Wigley hull in nonlinear wave is simulated.