Numerical evaluation of force coefficients of a yawing flat plate

In this paper the coupled role of the keel vortex and of the wave phenomena on hydrodynamic loads are investigated in the case of a yawed flat plate piercing the free surface and moving along either a straigth course or a circular path. The flow is studied by means of an inviscid rotational model based on a integral representation for the velocity field in terms of source and surface vorticity distributions. The related integral equations are numerically solved by coupling a source panel technique together with the vortex lattice method for treating the surface vorticity integrals. The free surface conditions are linearized, while the vortex shedding has been modelled in a simplyfied nonlinear manner. Extended comparisons with experiments and previous numerical computations show the importance of modeling the keel vortex shedding for the correct prediction of the. hydrodynamic loading. Beside, the role of free surface in determining the forces is discussed. In particular, it is numerically shown that for increasing Froude number the standard double model linearization leads to a significant overprediction of loads while the simpler Kelvin free surface condition appears to be more suitable for dealing with high Froude number cases.