RANS simulations of a 3D sheet-vortex cavitation

Abstract

On marine propellers, cavitation appearance and development is critical for performance and erosion considerations. Behind a ship, the propeller experiences all kinds of cavitation types, varying from sheet and bubbles to tip vortex cavitation. When a cavitation analysis is required, two methods are available: experimental or numerical. To find the optimum propeller that fits into different configurations and requirements, designers need accurate predictions within reasonable time. The experimental method is typically used at the end of a design process to verify performance. Therefore, quick and accurate numerical predictions are essential at different stages in the design process, to evaluate performance and cavitation patterns. Mathematical methods range from basic panel codes to the more complex ones, derived from the Navier-Stokes equations. Methods like DES and LES require large meshes and small time steps which makes their usability limited. The most practical viscous numerical method available at the moment in industry is Reynolds Average Navier-Stokes (RANS). The current paper will present the results of a RANS simulation of a 2D sheet cavity and a 3D sheet-tip vortex cavitation. Accurate results of these basic simulations are steps towards the end goal, cavitating propeller simulations. In this method the viscous effects are taken into account with aid of a two equation turbulence model, which results in a reasonably fast approach due to reasonably grids requirements. It is concluded that the RANS method can predict complex 3D sheet-vortex cavitation development and shedding. In addition, it is appropriate for industrial use because it achieves reasonably quick and accurate results. As a next step in the research project, the cavitation development on a propeller will be analyzed with this method.