| Based on the advantages of the existing propulsion system,this paper presents a novel pump jet thruster with no tip vortex.In view of the designed pump jet propulsion system,this paper analyzes the hydrodynamic performance as well as the vibro-acoustic characteristics,and compares it with the traditional pump jet thruster with clearance existed.The primary work includes:(1)The overall configuration design of the pump jet thruster is completed.Based on the traditional shaft-driven method,the new thruster has a rotor with a ring,by which the tip clearance and tip vortex are eliminated.By means of water lubrication and elastic support,the resistance moment are reduced and the vibration of rotor is absorbed,so that the fluid excitation and the coupling vibration and noise between the moving parts and the stationary parts are reduced with high efficiency assured.(2)The hydrodynamic numerical simulation of pump jet thruster is carried out.The large eddy simulation(LES)with moving mesh is employed to formulate the unsteady flow field of the thruster.And the hydrodynamic performance,flow characteristics and fluctuating pressure on the key surface of structures are analyzed.(3)A fully coupled finite/boundary element model(FEM/BEM)is developed to evaluate the vibro-acoustic responses of the underwater structure with unit-excitation source.The wet mode and the acoustic radiation are obtained,which provide a theoretical support for the vibro-acoustic response by the flow-induced forces in the future work.(4)The acoustic radiation of the pump jet thruster is analyzed from two aspects: the structural vibration noise and the flow noise.Based on the analysis of the vibro-acoustic responses with unit-excitation source,the fluctuating pressure obtained is transformed into structural excitations and the vibro-acoustic response induced by the structural vibration is provided.The Ffowcs Williams and Hawkings(FW-H)acoustic analogy formulation model is added to calculate the flow noise.Moreover,the influences of the advance coefficient with new/old pump jet thruster on the hydrodynamic properties and vibro-acoustic responses are also presented.The simulations in this paper provide a guideline for the vibration and noise reduction design of the thruster with a similar structure in engineering. |
