Numerical Simulation Of Cavitating Hydrofoils And Propeller

The propellers are the most important propulsions of modern ships. With modern shipsspeediness and hidden to demand more and more, the studies in dynamic performance andcavitation of propellers have been the main research contents in shipbuilding, which are theshipbuilding industry closely concern about. Due to the requirements of the speediness,Cavitation will inevitably occur on propellers.When cavitation occurs on propellers，thepressure fluctuations of hull will increase dramatically.And cavitation causes the hullcorrosion and noise.So the studies in dynamic performance and cavitation of propellersmainly are to improve the efficiency of the ship.In this paper, the cavitation performance ofhydrofoils and propellers is predicted, mainly using numerical methods. A complete set ofcalculation program to cavitation performance of two-dimensional hydrofoils,three-dimensional hydrofoils and propellers are set up.The partially cavitatiing problem of two-dimensional hydrofoils, three-dimensionalhydrofoils and propellers is treated using nonlinear theory by employing a low-orderpotential-based boundary-element method. The cavity shape of two-dimensional hydrofoils isdetermined in the framework of two independent boundary-value problems; in the first, thecavity length is specified and the cavitation number is unknown, and in the second thecavitation number is known and the cavity length is to be determined. In each case, usingmixed-iteration methods, the position of the cavity surface is determined in an iterativemanner until both a prescribed pressure condition and a zero normal velocity condition aresatisfied on the cavity.The boundary element method is then extended to treat the partially cavitatingthree-dimensional hydrofoils and propellers problem, using the kutta condition. Thethree-dimensional kinematic and dynamic conditions are applied on the surface underneaththe cavity. The cavity planform at a given cavitation number is determined via an iterativeprocess until the thickness at the end of the cavity at all spanwise locations becomes equal toa prescribed value(in our case,zero).Through calculating some examples， the method of predicting cavitatingtwo-dimensional hydrofoils, three-dimensional hydrofoils and propellers problem is shown to feasible. In the end，some influence factors of hydrofoils and propellers cavitation areanalysed.