Research On Vibration And Acoustic Characteristics And Vibration Reduction Measures Of Fluid Conveying Pipelines Based On Acoustic-Solid Coupling

Fluid conveying pipeline has become an indispensable part in the fields of ocean engineering,machinery,military industry and so on.It is an important tool to transfer fluid medium.During the process of equipment startup and pipeline operation,there will be vibration and sound wave transmission in the pipeline.Severe vibration will lead to pipeline rupture and fluid leakage,and the serious noise will affect the normal life and production of workers.Therefore,the analysis of the vibration and acoustic characteristics of fluid conveying pipelines and the study of vibration reduction measures provide a certain theoretical basis for pipeline fault sound detection,which is of great significance to the safety of pipeline transportation.Pipeline vibration and sound is a complex coupling process.It is not enough to consider only one-way coupling in pipeline vibration and sound research.It is necessary to consider the interaction between fluid and pipeline at the same time.Based on the theory of acoustic-solid coupling,the eigenmode of fluid conveying pipelines with different pipe wall characteristics,the elastic wave propagation law of different fluid media and the vibration and acoustic radiation characteristics of partially submerged pipeline were studied,and the modal comparison experiment of a single pipe with and without dampers is carried out to verify its vibration reduction effect.The specific research is mainly carried out from the following four aspects.Firstly,the vibration and acoustic problems of the pipeline and the theory of acoustic-solid coupling are analyzed and explained.A two-dimensional single-layer pipeline numerical model is established based on the theory of acoustic-solid coupling,and the dispersion curve of the pipeline mode is solved by parametric scanning.The dispersion characteristics of elastic wall pipeline with air,water and crude oil are analyzed.The influence of elastic wall,hard sound field wall and different wall thickness on the dispersion characteristics of the pipeline are studied.The results show that the distribution of sound pressure in the pipeline is basically the same under different wall conditions.The dispersion characteristics of liquid or gas inside the pipeline are quite different,the dispersion characteristics of water and crude oil are different in the direct mode.Due to the acoustic-solid coupling effect,the number of modes of the elastic pipeline increases.The change of the cut-off frequency of elastic wave mode is caused by the change of wall thickness.Secondly,the dispersion characteristics of elastic wave in sandwich pipeline filled with inner and outer steel pipes are analyzed.The Timoshenko beam model is used to derive the wavenumber analytical formula of elastic pipeline.Based on the theory of acoustic-solid coupling,the wavenumber and the sound pressure stress distribution of the coupling between the elastic wave of the pipeline wall and the acoustic wave of the fluid in the two-dimensional sandwich pipeline are solved.The dispersion relationship and guided wave mode in the case of water and air in the fluid domain in pipeline are calculated,and the cut-off frequencies of different orders are solved.The results show that the analytical solution and numerical solution of the dispersion curves of different media in the sandwich pipeline are basically consistent.The bending mode will deviate after a certain frequency.The results verify the feasibility of using the Timoshenko beam model in sandwich pipeline.Thirdly,the vibration and acoustic radiation of partially submerged pipelines is studied.Considering the effect of internal and external flow field,the underwater sound pressure stress distribution of pipeline with different immersion depth is calculated,and the underwater sound pressure level change curve of pipeline with different excitation frequency at different positions is calculated.The research shows that the underwater sound pressure level change curve form is consistent at the same immersion depth.Finally,the solid mechanics and acoustics module of COMSOL Multiphysics and the Modal and Acoustic modules of ANSYS were used to establish the finite element model of the pipeline at the same time,The modal experiments of the pipeline with and without damping plates are carried out respectively,and compared with the simulation results.The vibration reduction effect of adding damping plates at different positions of the pipeline is verified.It shows that the acoustic-solid coupling theory is feasible for the research of pipeline coupling characteristics.