A theoretical and numerical procedure for predicting sailing yacht lift and drag

Abstract

In this thesis, a theoretical and numerical procedure for predicting the effects of viscosity on the hydrodynamic forces developed by a sailing yacht hull is presented. A simultaneous viscous/inviscid algorithm is developed by coupling a low order panel method with quasi three-dimensional integral boundary layer equations. A transom condition is used to prevent non-zero wave heights at the stern for a hull with overhangs. The influence of viscosity on the outer inviscid flow is modeled using a wall transpiration boundary condition and an edge velocity formula. The boundary layer edge velocity is expressed as a sum of the inviscid velocities and a correction dependent only on the boundary layer variables, determined by equations developed from the panel method calculation as a distribution of transpiration sources. These are superimposed on the body, including the lifting surfaces, as well as on the potential flow wakes. The boundary layer equations, with the global potential flow effects included via the transpiration source model, are solved by a full Newton's method. Numerical predictions for a sailing yacht hull are compared with experimental results obtained in a towing tank.