FLUID STRUCTURE INTERACTION ANALYSIS OF AN HYDROFOIL

In this paper, a dynamic computation of the Groupama 3 foil is performed. Foils are thin profiles, placed under the hull of a ship, allowing it to provide a lifting force. This study is placed in the context of the 2013 America's Cup, which will see the appearance of a new kind of high performance multihull. At high speeds, the foils are subject to intense hydrodynamic forces and to movement due to the sea. The deformations are then sizable and there is a risk of ventilation, cavitation or vibration that could lead to important modification of the hydrodynamic forces or to the destruction of the foil. It is therefore necessary to quantify correctly its deformation and its response to dynamical efforts. The foil/water interaction is a strongly coupled problem, due to the thickness of the object. In this paper, the problem is solved using a segregated approach. The main problems resulting of such a method are the numerical stability and remeshing. These problems are detailed and some results presented. As a first test case, the simulation of a vortex excited elastic plate proposed by Hubner is presented. This case is very demanding in terms of coupling stability and mesh deformation. Then, the foil of Groupama 3 is modelled in a simplified form without hull and free surface, and then in a more realistic conditions with free surface and waves.