Research On Propeller Cavitation Characteristics And Low Noise Propeller Design

With the development of underwater detective equipment, ship acoustic stealthy technique becomes a popular problem within shipbuilding researcher. Thus, propeller cavitation radiated noise as one of three primary noise source has drawn more and more attention. The paper mainly investigates propeller cavitation noise from theoretical aspect and experimental aspect, and establishes a optimization design method for the aim to reduce propeller cavitation radiated noise.When a propeller works in the unsteady inflow behind stern, transient cavitation will appear, and bring down the ship stealthy performance because of the induced considerable radiated noise. For the purpose to decrease the cavitation radiated noise, it's necessary to delay or void the appearance of cavitation when a propeller is designed. A wider bucket is effective to improve the cavitation performance of a propeller.The dissertation analyzes the technology features of cavitation radiated noise, introduces current technology situation of cavitation noise. From the key technologies to reduce the cavitation noise, The dissertation establishes a optimization design method for the purpose to reduce propeller cavitation radiated noise.The dissertation investigates the hydrodynamic performance of the propeller with theoretical method, and compiles the corresponding numerical program, which includes steady hydrodynamic performance prediction and unsteady hydrodynamic performance prediction. Steady hydrodynamic performance prediction is solved with low-order panel method based on velocity potential, the integral equation is derived from Green formula, the border condition including rigid object condition, the far distance condition and Kutta condition. Unsteady hydrodynamic performance prediction is solved by time domain method. The dissertation uses key blade method to reduce the computing time , the unknown parameters of other blades are derived from the key blade by the corresponding phase angle. At every time step a linear algebraic equation established on a key blade is solved numerically combined with the Kutta pressure condition.The dissertation predicts the propeller cavitation shape, including cavitation extent, cavitaiton thickness and volume, the integral equation is derived from Green formula, the solution condition including kinematic condition, dynamic condition, rigid object border condition, the far distance condition and Kutta condition. calculation results are in good agreement with the experimental data. The dissertation analyzes the cavitation problem with experimental method, notes the transient process as the foundation of verification foundation of mathematical method. The dissertation simulates the transient process of cavitation with software, so it's more clearly to analyze the movement of cavitation.The dissertation discusses the effect of different parameters on propellercavitation performance, and develops an optimization design method for the purpose to reduce propeller cavitation radiated noise. Use panel method as the basic numerical method, adopt spline surface to simulate the shape of blades. When the propeller rotates in the unsteady inflow, the spline function is adjusted according to the pressure distribution of blade section. So the thickness distribution and camber distribution of blade section are adjusted to get a smooth pressure distribution. As well, the minimum pressure is increased to delay the emergence of cavitation. The experiment shows that the design propeller has a lower cavitation noise than the original propeller.