Theoretical Prediction Of Propeller Cavitation Performance

With the worldwide development of ship, the high speed and power of the ship are demanded for higher level. But the propeller's dimensions limited by various conditions can't increase randomly, the load on the blade is increasing continually, in this situation, the cavitatuon phenomenon will appear inevitably. The cavitation will lead to some bad effects on propeller performance, such as lowering the speed, the blade erosion, the unexpected structure vibration and radiated noise and so on, so it is necessary to predict the propeller's cavitation performance in the ship design.This paper has analyzed the technology features in the domestic and foreign research of propeller performance and introduced the current technology of propeller cavitation. Some difficulties and tentative approaches in the research of cavitation performance have been referred.This paper has investigated the hydrodynamic performance of the propeller in the uniform and non-uniform flow field with theoretical method, which includes steady hydrodynamic performance and unsteady hydrodynamic performance. Unsteady hydrodynamic performance prediction is solved by time domain method. The key blade method has been used in order to reduce the computing time and storage, the unknown parameters of other blades are derived from the key blade by the corresponding phase angle. At each time step, the method is the same as the steady condition.This paper has adopted the low-order surface panel method based on velocity potential to predict the performance of partially cavity, which includes cavitation extent and thickness, and has compiled the corresponding numerical program. The solution method is carried out for each chordwise string. It is used of the cavitation happen condition to solve the cavitation extent combined with the pressure distribution in the unsteady hydrodynamic performance calculation. To predict the cavitation thickness, the integral equation is derived from Green formula, the solution condition including kinematic condition, dynamic condition, rigid object border condition, the far distance condition, the pressure Kutta condition and the zero thickness of cavitation trailing edge condition. Based on the kinematic condition on the cavitation panel, the cavitation thickness can be predicted by the solved source strength.Through the verification calculation on PHS01 propeller and compared with the test report, the computer program presented on this paper can give a satisfied result of cavitation performance, so this method is reasonable in theory.