A boundary element method for the strongly nonlinear analysis of surface-piercing hydrofoils

A two-dimensional BEM based scheme is presented for the numerical modeling of the ventilated flow past a surfacepiercing hydrofoil. Fully nonlinear boundary conditions are applied on the free-surface allowing for the modeling of the jets generated as a result of the passage of the hydrofoil through the air-water interface. The scheme is validated through a comparison with self-similar solutions in the case of nonventilating entry and with experiments in the case of ventilating entry. Results are presented for fully wetted and ventilating cases with and without the effects of gravity. Preliminary results are presented for the case of a hydrofoil in rotational motion, simulating the ventilation characteristics of a typical surface-piercing propeller. The fully nonlinear scheme is a step towards quantifying the errors associated with some of the linearizing assumptions made in a 3-D boundary-element tool (PROPCAV) for the modeling of surface-piercing propellers..http://deepblue.lib.umich.edu/bitstream/2027.42/84281/1/CAV2009-final97.pd

Prediction of cavitating flow around 3-D straight/swept hydrofoils

A boundary element method (BEM) model is applied for prediction of cavitating flow around 3-D straight/swept hydrofoils between slip (zero shear) walls. The governing equation and boundary conditions are formulated and solved by assuming piecewise constant distribution of sources and dipoles on the hydrofoil and cavity surfaces, and piecewise constant distribution of dipoles on the trailing wake sheet. Cavity shape determination is initiated with a guessed cavity planform, and the cavity extent and thickness are determined iteratively until the dynamic and kinematic boundary conditions are satisfied on the cavity surface. To account for no-normal flow through the side walls, the method of images is used. For the fully-wetted case, the attached flow results obtained are compared with results from a full-fledged Reynolds-Averaged Navier-Stokes (RANS) solver. The cavitating results for a straight wing between slip walls are compared with results from an existing 2-D BEM solver for cavitating flow around hydrofoils. The RANS solver is also used to study separated flow characteristics around 2-D/3-D hydrofoils at high loading.http://deepblue.lib.umich.edu/bitstream/2027.42/84279/1/CAV2009-final94.pd

IABEM 2002

Computational Mechanics 32(6), special issu

A BEM for the Propagation of Nonlinear Planar Free-surface Waves

A Boundary Element Method (BEM) model for the propagation of non- linear free-surface waves is described and its application to the study of the hydrodynamic characteristics associated with the roll-motion of 2-D hull sec- tions is presented. The roll-motion of the hull section is modeled as a mixed boundary value problem and solved using a higher-order (linear strength dis- tribution) BEM coupled with a Mixed-Eulerian-Lagrangian (MEL) scheme for the time-dependent free-surface boundary conditions. Applications, that in- clude the propagation of fifth-order Stokes waves and waves generated by a piston wave-maker, used to validate the BEM scheme prior to its application to the hull roll-motion are also described