Added Mass and Damping of Oscillating Bodies: a Fully Viscous Numerical Approach

The prediction of the motion of a ship, as a rigid body, advancing in waves is classical problem in naval architecture. The vast majority of numerical approaches calculates the forces acting on the ship hull by considering an inviscid and irrotational fluid. Unfortunately, especially for motions in the transverse plane as roll or sway, and for particular ship hulls, viscous effect are absolutely non-negligible. The paper presents a first step toward a development of a seakeeping solution method based on fully viscous solvers to evaluate the radiation forces on the hull and hence the hydrodynamic coefficients of damping and added mass appearing in the generalized equation of motion. For the scope, the direct numerical solver of Navier Stokes equations, based on finite volume technique, is implemented and applied to the case of forced oscillation of 2D simple bodies, using the open-source libraries of OpenFOAM. The improvement against traditional potential flow based theories is evident, but in particular cases some improvements need to be done yet.