Prediction Of Unsteady Cavitation Performance Of Propeller By Lifting-Surface Theory

With the development of ship in large-scale and high-powered, the load on the blade is increasing continually and the velocity field behind the ship is non-uniform, the unsteady cavitation will appear on the surface of blade inevitably. The unsteady cavitation will lead to some damage such as blade erosion, the vibration of ship structure and the propeller noise, or even effect the hydrodynamic performance of propeller seriously, therefore, the correct prediction of unsteady cavitation of propeller is possess of important theoretical and practical value in the assessment of how to reduce or avoid these damage, the prediction of unsteady shaft forces of propeller, the calculation of the vibratory forces and the design of unti-cavitation blade section.As the popular method for the calculation of marine hydrodynamics, the surface panel method has the advantage over the lifting-surface method in the mechanics model and the prediction of pressure distribution, but for the total force of propeller, they have the same computational accuracy. Using the surface panel method for the unsteady cavitation of propeller needs a very huge calculation work and the solution is instable, relatively, the lifting-surface method is more mature, the calculation is more rapid and stable, therefore, using the lifting-surface method for the unsteady cavitation of propeller is still have important engineering practical value.This paper has adopted the lifting-surface method for the prediction of unsteady hydrodynamic performance and cavitation performance of propeller. The intensity of vortex lattice and cavitation source on the key blade is solved by iterative scheme in time domain. There are several processing mode of the unsteady Kuta condition, a appropriate choice will improve the convergence velocity of iterative, this paper has choosed the dipole intensity near the training edge is polynomial distribution to satisfy the unsteady Kuta condition by compare experiment. In order to improve the efficiency of solution, a chordwise strip iterative method is adopted to determine the cavitation range of blade, the interaction between strips is included by spanwise iterative procedure.The prediction of unsteady cavitation performance of propeller is studied by using lifting-surface method systematically, and an intact computer program for the prediction of unsteady cavitation performance of propeller is set up in this paper. Through the verification calculations on DTNSRDC series propeller and HSP highly skewed propeller, the computer program presented in this paper can give a satisfied result of open water performance of propeller, unsteady forces, unsteady pressure distribution of blade surface and cavitation performance.Using the method presented in this paper to predict the unsteady cavitation of propeller has important engineering value in the calculation of the propeller vibratory forces and the off-design of propeller.