Numerical and experimental study of a nearby solid boundary and partial submergence effects on hydrofoil added mass

Abstract

The influence of the boundary conditions on the added mass of a NACA0009 cantilever hydrofoil has been numerically and experimentally investigated. The study has been focused on the effects of a lateral solid wall close to the hydrofoil tip side and of a partially wetted vertical hydrofoil at different levels with the free surface parallel to the span. A detailed fluid–structure model has been built for both cases and a modal analysis has been carried out. The numerical three first natural frequencies have been used to calculate the added mass coefficients. These coefficients have been compared with the results of the analogous experiments carried out by means of an onboard excitation and response system based on piezoelectric patches. The obtained results are in reasonable good agreement with experimental data. The proximity of a lateral solid wall provokes an increase of the added mass experienced by the hydrofoil which can be approximated by a 2nd order polynomial function for both bending and torsion modes. On the other hand, the increase of the added mass with the level of partial submergence is found to be dependent on the relative displacements of the hydrofoil submerged part and hence on the mode shape.