Numerical Simulation Of Tip Vortex Cavitation In Propeller

With the increase of ship power demand,the hydrodynamic load of propeller is increasing,so the cavitation phenomenon of propeller is difficult to avoid in many cases.The tip vortex cavitation will not only bring significant cavitation noise,but also cause denudation on the rudder surface,which has a very adverse effect on the stealth of ship sound.Improving vortex cavitation at the tip of propeller has become an important part of ship propeller theoretical design and performance prediction.Therefore,it is of great significance and engineering value to study and predict the cavitation phenomenon of propeller tip vortex.Computer Fluid Dynamics technology is becoming more and more mature,which makes it widely used in ship field.On the basis of CFD technology,this paper uses STAR-CCM+software to study propeller,which is mainly divided into the following aspects:By taking NACA 16020 elliptical hydrofoil as an example,the hydrodynamic characteristics of the hydrofoil are calculated,the velocity,pressure and vorticity distribution of the wake field and the generation and development of the tip vortex are analyzed,the cavitation of the elliptical hydrofoil surface and the cavitation of the wing tip are predicted,and the accuracy of the numerical simulation results is verified compared with the experimental values.Taking marine E779 A propeller as the research object,the large eddy simulation method and Schnerr-Sauer cavitation model are used to simulate the tip vortex cavitation of propeller.At the position where tip vortex cavitation may occur in propeller,spiral tube is used as volume control to form spiral infill mesh,and the tip vortex cavitation of E779 A propeller is simulated more precisely.The experimental and numerical simulation results show that this method has good numerical prediction accuracy,and the thrust,torque coefficient and open water efficiency are more consistent.On this basis,the numerical simulation of tip vortex cavitation based on spiral encryption grid is carried out.Through the simulation results,it can be seen that the flow of spiral encryption region is simulated more finely,and the velocity and pressure distribution of encrypted tip vortex are clearly displayed.The comparison of numerical and experimental cavitation results shows that this method can predict the cavitation of propeller,especially the shape and law of tip vortex cavitation.Based on marine E779 A propeller,four propellers with the same blade geometry but different blade number were studied.The open water performance and cavitation phenomenon of propeller are predicted and analyzed,and the mechanism of tip vortex formation is revealed.the flow characteristics around cavitation and tip vortex cavitation of propeller blades under different blade numbers are analyzed.the effects of blade numbers on the surface ring amount of propeller blades are compared.the axial velocity and axial vorticity of propeller wake in wake are visualized.the formation and evolution of near wake tip vortices are discussed.The results show that the thrust and torque on a single blade will decrease with the increase of the number of blades,but the thrust and torque on the whole propeller disk surface will increase obviously,and the efficiency will also decrease,which is consistent with the experimental value.