A Numerical Study of Cavitation Induced Vibration

Abstract

The present work deals with an original study of the dynamics of an elastic structure immerged in an unsteady partial cavitating flow. The latter corresponds to the case of a leading edge attached cavity that exhibits periodical oscillations. The elastic structure is a cantilevered rectangular hydrofoil made of polyacetal plastic material (E = 3GPa). The computational fluid dynamics is based on a 2D unsteady single fluid model of cavitation with a barotropic law and a k – ε – RNG modified turbulent model. The computational structure dynamics is carried out using a 3D finite element code. The fluid structure coupling is based on a chained weak coupling algorithm for which the 2D unsteady local fluid loading is computed on a rigid hydrofoil, then interpolated on the 3D deformable hydrofoil to compute the structural dynamics. The results are compared to the experiment ones carried out in the hydrodynamic tunnel of the research institute at the French Naval Academy for flow conditions close to the numerical ones. It is shown that in spite of a weak coupling algorithm, the forced vibration due to the periodical behaviour of the unsteady partial cavity is rather well predicted by the computation and compared favourably with the experiments. However, the experiments reveal that cavitation influences the natural modal response of the elastic structure in a more complex fluid structure interaction process.