Flow separation model for the water impact problem

Abstract

. The present paper proposes a new flow separation model for the water impact problem which is here solved through by a potential flow model with fully non-linear boundary conditions at the free-surface. The unsteady boundary value problem is numerically solved through a hybrid BEM-FEM approach where a boundary element method is coupled to a simplified finite element method for describing the thinnest part of the jet. In the water entry of bodies with smoothly curved surface, the point where the flow detaches from the body contour is unknown and has to be computed as a part of the numerical solution. For this reason, the hybrid BEM-FEM approach is here extended to include a flow separation model based on a kinematic criterion. The proposed model is applied to the water entry of different smoothly curved body with a constant vertical velocity. Numerical results show the capability of the formulation to accurately describe the free-surface evolution and pressure distribution as well as to provide a consistent prediction of the flow separation.