Numerical And Experimental Research On Propeller-Induced Pressure Fluctuations And Cavitation In Non-uniform Flow

This paper has adopted the low-order surface panel method based on velocity potential to predict the unsteady performance of propeller. The computer program has following advantage: the solution of main blade is by iterative scheme in time domain, the Kutta condition is used by explicit equal pressure condition, the Jacobian matrix which can reflect the influence on the difference between the upper and lower surface at trailing edge by dipole is calculated in each iterative procedure, in order to improve the convergence of iteration. Through the verification calculations on various types of propeller, the numerical method and computer program presented in this paper can give a satisfied result of open water performance of propeller, unsteady forces, pressure distribution of blade surface.This paper has presented the calculation formula and numerical solution methods to determine the range and volume of partially cavity, supercavity by using surface panel method, and has predicted the range and volume of unsteady cavitation of propeller by using surface panel method for the first time inland. To improve the efficiency of solution, the solution method to determine the cavitation range of blade is carried out for each chordwise string, the interaction between strings is included by spanwise iterative procedure. The unknown source strength of cavitation is always arranged on the propeller blade surface in the solving process, but the integration is carried out along the cavity surface of last iterative step when the strength of cavitation dipole is determined according to dynamic condition. The propeller cavitation range determined by calculation method presented in this paper agrees with the observation result of cavity image at cavitation tunnel very well, which proves the practicability of this method.Presently most of the theoretical method to predict the propeller-induced hull pressure fluctuation is based on the calculation method in which the pressure is induced by pulsating source in infinite flow. The calculation method is adopted and the corresponded computer program is complied. The propeller-induced hull pressure fluctuation due to blade thickness, blade load, cavity thickness and the change of the cavity volume can be analyzed respectively in the computer program. The better agreement between the calculated value and the measurement result of propeller-induced hull pressure fluctuation proves that the program in this paper can be suitable for engineering application.With the fund item sponsored by the National Laboratory of Hydrodynamics, the study on measurement method of propeller-induced pressure with using self-propulsion model has been carried out in depressurized towing tank. The advantage and disadvantage of measurement of propeller-induced pressure by using different equipment is discussed. The method to obtain self-propulsion point for full scale in depressurized towing tank is studied. The measurements of pressure of two propeller models are carried out, the results of the measurement agree with those obtained by cavitation tunnel very well, which proves this measurement is successful, and the theoretical prediction is verified too.The prediction of propeller-induced hull pressure fluctuation in non-uniform flow is studied by using theoretical calculation and model experiment systematically. An intact method and computer program for the prediction of unsteady cavitating propeller-induced hull pressure fluctuation in non-uniform flow is set up in this paper. The measurement of propeller induced hull pressure fluctuation in depressurized towing tank carried out in this paper is the first time inland.