Research On Sound Radiation Characteristics And Noise Source Separation Technology Of Nozzle Of Sea Pipeline

Acoustic stealth performance is an important factor in evaluating the performance of underwater vehicles,and it is related to the combat capability and concealment of underwater vehicles.The sea pipeline system is one of the main sources of radiation noise of underwater vehicles.The various noises introduced by pumps,valves,elbows and other equipment in the system will radiate outward at the nozzle,and the fluid in the tube will be sprayed outward at the nozzle.Flow noise is also introduced,which makes the noise characteristics of the pipelines of the sea pipeline relatively complicated and destroys the acoustic stealth performance of the underwater vehicle.Therefore,the research on the acoustic radiation characteristics and separation technology of the pipelines in the sea pipeline has important guiding significance for objectively evaluating the vibration and noise reduction effects of the underwater vehicle.By evaluating the contribution of the noise sources of the nozzles,the main noise sources are analyzed.It is beneficial to achieve effective control of the noise of the sea pipeline system.In this paper,the acoustic transmission characteristics of sea pipeline are studied firstly.Actran acoustic simulation is used to analyze the acoustic field characteristics of different materials with different diameters.The simulation results are compared with the experimental results.The results show that for the liquid-filled tube of the same material,the cut-off frequency of the tube increases with the diameter of the tube,and the sound wave lower than the first-order cutoff frequency cannot propagate in the tube for a long distance;on the other hand,the transmission capacity is better.Strong metal pipes,sound waves below the first-order cutoff frequency are transmitted through the pipe wall in the form of vibration.The above conclusions laid a solid foundation for the subsequent separation test of nozzle noise sources.In this paper,the flow field model of sea pipeline nozzle is established by ICEM and the mesh division is completed.The Realizable k-e model and large eddy simulation method are used to calculate the steady-state and transient fields respectively in Fluent,and the flow field characteristics are analyzed in detail.Then,using the Lighthill acoustic analogy method in Actran,the sound field numerical calculation of the flow noise generated by the fluid at the nozzle is carried out,and the relationship between the nozzle flow noise and the flow field and its acoustic radiation characteristics are given.Finally,the experimental study on the separation of noise sources in the pipelines of sea pipeline nozzle were carried out,and themeasurement method of pipeline noise in the whole frequency band was proposed.The cutoff frequency of the non-anechoic pool was measured by the reverberation method to measure the sound radiation of the nozzle,which was lower than the cutoff.The frequency is measured by the direct method.On the basis of the control variables,the noise source separation test of pumping straight pipe elbow,pump hose elbow,high water tank hose and other working conditions was carried out,and different noise source pairs were analyzed.The contribution of noise.The numerical calculation and experimental results show that the radiation noise characteristics of the fluid generated by the nozzle injection meet the characteristics of the quadrupole source,and the radiated sound power is proportional to the 8th power of the flow velocity.The simulation and the test have good consistency,but the overall flow.Compared with the noise of the pump,the noise has little contribution to the acoustic radiation of the nozzle;the mechanical noise generated by the pump in the sea pipeline system of is transmitted through the vibration of the pipe wall,and the hose can be effectively restrained by connecting the vibration isolation;the pipeline system The main contribution of the pulsating pressure to the nozzle noise is derived from the vibration noise generated by the excitation structure,while the direct radiation of the pulsating pressure at the nozzle is relatively small;the mechanical noise caused by the pump and the structural vibration noise and the vibration generated by the pulsating pressure excitation structure noise plays a major role in nozzle noise.