Numerical investigation of waves slamming on a rotating flap in free motion using a fully nonlinear HOBEM

A time-domain higher-order boundary element method (HOBEM) with fully non-linear boundary conditions is established to investigate the slamming problem on a rotating flap in free motion. The mixed Eulerian-Lagrangian (MEL) boundary conditions with numerical damping layers are adopted to track the time-dependent free surface nodes, through which the influences of coupled disturbed waves from the outer boundaries are eliminated. The potential of each element within the thin long jet is calculated in the rotating coordinate system to overcome numerical instability induced by the local highly oscillatory pressure. The domain decomposition method and the unequal distribution scheme of meshes are simultaneously adopted to capture the falling jet with strong non-linearity. The auxiliary function method is then employed to calculate the pressure distribution, through which the mutual dependence between the body motion and the fluid flow is decoupled. The present numerical model is verified through comparing the flap motion response, dynamic characteristics and free surface elevations against the published experimental data and the Computational Fluid Dynamics (CFD) results. The parameter studies are performed to investigate the influences of flap properties and wave parameters. Detailed results are provided through free surface profile, rotation angle, angular velocity, torque response and pressure distribution.