Numerical Simulation Of Cavitation Flow Of Submerged Water Jet Based On Fluid Compressibility

In the cavitation jet,the collapse of the cavities can bring great pressure shock,which greatly improves the operating efficiency of the jet,and the submerged water jet technology has gained people's attention because it can generate a large amount of cavitation during the jet process.The submerged water jet technology has the advantages of strong erosion energy,less material loss,and environmental protection.It has been applied and researched in many aspects,such as cleaning and crushing of materials,separation of toxic substances,and sewage treatment.This paper uses Fluent to simulate the complete cavitation process of submerged nozzle jets,and verifies and analyzes the calculation results.The main contents are:(1)The first chapter introduces the research status of submerged cavitation jets at home and abroad,discusses the background and significance of the subject research,and determines the key content of the subject research.(2)The second chapter briefly introduces the mathematical model needed for numerical calculation in this paper.(3)In chapter three,on the basis of selecting suitable boundary conditions,the model is simulated based on the compressibility of the fluid,and the calculated results are compared with the existing experimental data to verify the established calculation model,at the same time,the Mesh independence of the model is analyzed.(4)In chapter four,the turbulent viscosity correction method is introduced,and simulation calculations are performed under different turbulent viscosity correction conditions.It is found that when the value of the index n in the density function is higher,the cavitation in the flow field will be more severe.In the flow field with more cavitation,the attenuation of the jet velocity will be slower,and the jet energy can be transmitted to a farther position.(5)In chapter five,we observed the complete evolution of cavitation in the submerged jet,and found that cavitation first occurred at the throat entrance,and the bubble cloud gradually expanded during the downstream movement,the growing bubble cloud will periodically fall off and collapse at the nozzle outlet.The cavitation collapse shock wave was studied and analyzed,and it was found that when the cavitation cloud collapses,a severe instantaneous pressure pulse is generated.The shock wave is transmitted very quickly,and its propagation will have a significanteffect on the pressure distribution of the surrounding flow field,speed up the collapse process of the surrounding cavitation clouds,and inhibit the newly generated attached cavitation movement.The development process of the re-entrant jet in the flow field and the velocity change of the near-wall point caused by the re-entrant jet are studied,and it is found that the re-entrant jet will cause a sharp velocity fluctuation in the position of the near-wall point.At the same time,the larger the size of the cavitation cloud in the flow field,the faster the speed of the re-entrant jet.In the end of this paper,all the research contents and conclusions are summarized,and the related aspects which can be further discussed are prospected.