Study On Underwater Structure Vibration And Radiated Noise Control Caused By Propeller Exciting Force

The analysis of underwater structure vibration and noise control is received more attention now. There are many literatures study the calculation methods and control methods for structure vibration and radiated noise. These analyses about underwater structure vibration and noise control focus on mechanical appliance noise, propeller noise and fluid dynamical noise. The problem that propeller exciting force transfers from shafting, the bearing supporting to structure, causing structure radiated noise is less studied now. By such problem solved, the underwater structure noise will be more decreased.The underwater structure vibration and noise caused by propeller exciting force are studied in this paper. The characteristic of structure radiated noise is studied. The methods of structure vibration and noise control are calculated. The experiment model is designed. The calculation methods and the validity of vibration control methods are examed.The calculating model of underwater structure with shafting is built. The vibration and radiated noise characteristics of underwater structure caused by longitudinal and lateral propeller force are analysised by FEM/DBEM in this paper. The flexural vibration of structure is mainly excited by lateral propeller force and the radiated pressure mainly distributes alone the length of structure. The distribution of radiated pressure is mainly in the axial direction of structure when structure excited by longitudinal propeller force. The amplitudes of response function of structure radiated sound power caused by longitudinal and lateral propeller force have same level, which prove that methods should be adopted to decrease the structure vibration and noise caused by both longitudinal and lateral propeller force.The methods that can reduce the radiated noise of underwater structure caused by longitudinal propeller force are studied in this paper. The effect of flexural base on the characteristic of transfer force and radiated sound power of structure is analysised. The different structure of thrust bearing supporting, the vibration isolator and dynamic vibration absorber are used to reduce the radiated noise of underwater structure.The methods that can reduce the radiated noise of underwater structure caused by lateral propeller force are studied in this paper. The calculating model that can simulate long axis hole is made. The effects of different stiffness of rear bearing, front bearing, thrust bearing and the distance of bearing on underwater structure radiated noise are studied. The releasing DOF of bearing supporting, installing the carbon fibre shafting, filling damping material and installing dynamic vibration absorber are used to reduce the radiated noise of underwater structure.The coupled shafting and structure vibration is studied by power flow method. Because of analysis model is complex, the finite element method is adopted to calculate the system input power, the transfer power at each bearing supporting and the energy distribution of structure. The effect of exciting force, exciting moment and inner fluid on chatacteristic of energy transfer and distribution is analysised. The effect of each vibration control method is studied by power flow method.The coupled shafting and structure experiment model is designed, which can measure the longitudinal, lateral exciting force at bearing supporting and the vibration reaponse on shafting and structure. The experiment modal analysis and forced vibration analysis is carried. The correctness of simulation method is examed and the characteristic of structure vibration is got. The devices of vibration control are designed and the validity of such methods on vibration control is validated.