Cavitation visualization and prediction of propeller characteristics of INSEAN E779A propeller using sliding mesh model

A Marine propeller is an ensemble of airfoil sections assembled in the form of a propeller blade. The pressure in the liquid adjoining to the body drops as the square of the local flow velocity as the propeller rotates. While the propeller rotates in water, the difference in stresses existing between the face and back of the propeller creates a thrust force in the forward direction, which lets it overcome the drag experienced by the vessel. Different methods are available to determine propeller performance, including experimental, theoretical and numerical. The open water propeller tests are conducted either in towing tanks/ circulating water channels to determine the non-dimensional propeller parameters such as Thrust co-efficient and Torque co-efficient and though accurate in the model scale are cumbersome and costly. The Computational Fluid Dynamics (CFD) techniques provide a reliable and robust solution to this problem.The current work presents the numerical prediction method to determine hydrodynamic performance characteristics of an INSEAN E779A propeller. The study is implemented using the commercially available computational fluid dynamics (CFD) solver, Ansys Fluent. The study utilized unstructured tetrahedral meshing along with wedge/prism-shaped elements in the boundary layer regions, with a Realizable k-ε turbulence model. The sliding mesh model is used to replicate the physics of the rotating propeller. The study has been carried out using Unsteady RANS. The solver employed is SIMPLE. Studies have been carried out using both first order upwind and second order upwind for pressure, momentum and transient formulation. However, it is seen that both the formulations give the same accuracy. A detailed study of time step estimation has been carried out to arrive at the most optimum time step without sacrificing the accuracy of the results.To capture the cavitation effect, the phases of water and air were formulated using the Mixture option in Fluent with Mass Transfer mechanism at cavitation and cavitation model as Schenerr-Sauer model.Results show reliable thrust coefficient, torque coefficient, and efficiency data for the case of low advance ratios. The cavitation is visualized by iso-surfaces of pressure below the vapor pressure and was validated by available photographs from experiments conducted in cavitation tunnel with “reasonable matching.”