| Pipelines in nuclear power plants produce violent vibration and noise under the action of fluid excitation force.The long-term vibration of the pipeline usually causes the vibration fatigue of the pipeline,which may lead to cracks in the pipeline,force the nuclear power plant to shut down for maintenance,and even cause catastrophic accidents.Therefore,it is necessary to study the flow-induced vibration,control the fluid fluctuation ability inside the pipeline and reduce the pipeline vibration to improve the safety of nuclear power plants.In this paper,the perforated plate is used to reduce the fluid fluctuation in the pipeline,which can effectively solve the problem of pipeline vibration in nuclear power plant.The perforated plate has the advantages of simple structure,low cost,convenient installation and easy maintenance.It has been widely used in nuclear power plants.At present,the application of perforated plate mainly focuses on the vertical interaction between the fluid and the perforated plate,which has a great influence on the flow rate.When the interaction form between perforated plate and fluid is parallel,perforated plate can also play the role of reducing vibration and pressure,and at the same time,it has little impact on the flow.Therefore,it is of great significance to explore the application of perforated plates in parallel flow.In this paper,the flow characteristics of perforated plates in parallel flow are studied,and the influencing factors are discussed,and the random vibration mechanism of the perforated plate in parallel flow is clarified,that is,the fluid fluctuation near the perforated plate can generate a fluid excitation force that changes with time to stimulate the perforated plate to make mechanical vibration.The method of effectively reducing the fluid fluctuation intensity near the perforated plate is found,which provides the theoretical basis for the application of perforated plate in parallel flow.In this paper,a series of studies on the pressure fluctuation characteristics of perforated plates in parallel flow are carried out by experimental research and numerical simulation.The research contents and results are as follows:First of all,seven test models of different structure combinations were designed by changing the hole diameter,hole pitch and cavity depth under the plate,and the wind tunnel test bed was built,and the experimental research was carried out.The pressure fluctuation characteristics of perforated plate surface were analyzed in this experiment.In addition,a simplified three-dimensional model is established by using commercial software UG.Then,the flow characteristics of each perforated plate were studied by using the commercial software ANSYS CFX 16.0.Combined with the experimental study,the pressure fluctuation root mean square value(RMS),spectral characteristics,streamline,pressurecontours and velocity swirling strength distribution near the perforated plate were discussed.It is found that the wind velocity,hole diameter and hole pitch are the key factors that affect the flow characteristics on the surfaces of the perforated plate,while the influence of cavity depth under the plate is negligible.The experimental results and numerical results show that the decrease of wind speed and hole diameter and the increase of hole pitch have significantly improved the reverse flow region and pressure distribution characteristics in the rear end cavity of the perforated plate.It is mainly reflected that the pressure distribution is more uniform near the perforated plate,and no high pressure zone appears.The flow in the tail space is more stable,and the vortex generation is relatively small.And the influence of the change of cavity depth under the plate on the pressure fluctuation on the surface of the perforated plate is almost negligible.Therefore,smaller wind speed,smaller hole diameter and larger hole spacing can effectively reduce the pressure fluctuation amplitude around the perforated plate,thus reducing the random vibration of the perforated plate. |
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