FSI ANALYSIS OF HYDROFOILS USING FEM AND SPH METHODS

Abstract

The purpose of this research was to investigate the advantages and disadvantages of coupled SPH-FEM analysis of a hydrofoil in regards to using FEM only approach. The both methods (SPH and FEM) are based on the continuum mechanics, however, SPH implementation uses Lagrangian material framework, while FEM uses an Eulerian formulation for the fluid analysis, and Lagrangian formulation for the solid analysis. In the case of combined SPH-FEM analysis, the hydrofoil is modeled with FEM, while the surrounding water is modeled with SPH particles. The contact between the two is done using nodes to surface algorithm, while if we use the FEM only, the weak coupling is done on the common interface nodes between Eulerian fluid domain and Lagrangian solid domain. The Lagrangian framework of the SPH means that we need to generate particles at one end, and to destroy them on the other, in order to generate a continuous fluid flow. The simplest way to do this is by using activation and deactivation planes, which is a solution implemented in the commercial LS-Dyna solver. Results show that velocity fields obtained by SPH-FEM coupling are similar to velocity fields obtained by FEM. FEM only solution has a clear advantage in regards to execution time, however, SPH-FEM coupling offers greater insight into phenomena such as cavitation, that justifies the extra computational cost.