Numerical Simulation Research On Film Formation By Multiple Direct-Injection Nozzles

Plate impingement jets are a common flow regime in fundamental research and industrial applications.Among them,the multi-direct nozzle jet film formation is particularly important,which is widely used in many fields,such as the atomization of liquid propellants in aerospace engineering and the high head discharge in hydraulic engineering.However,due to the difficulty of experiments,numerical simulation can effectively save experimental resources and precisely control variables,so it is increasingly used in research in this field.In addition,due to the complexity of the two-phase flow,the three-dimensional numerical simulation is usually difficult.Therefore,a steady three-dimensional numerical simulation method is established in this thesis to restore and study the physical process of the jet impinging on the plate to form a film.On this basis,combined with the unsteady threedimensional calculation,this thesis further improves the flow details of the multi-straight nozzle jet film formation.In this thesis,the basic theory and model of gas-liquid two-phase flow are firstly reviewed,and the VOF(Volume of Fluid)model is introduced in detail.The VOF model is suitable for the flow calculation of multiphase immiscible fluids,and is compatible with most turbulent flow models.After that,the construction of the geometric calculation domain and the mesh refinement method are analyzed,and the appropriate mesh division method is selected through the verification and analysis of the mesh independence.Then,an appropriate turbulence model is selected,and the numerical simulation results are compared with the experimental results,and a three-dimensional numerical simulation method is established.In this thesis a large number of calculations are carried out combining the steady threedimensional numerical simulation method and the unsteady constant value simulation method.After that,the effects of jet angle,jet velocity,dynamic viscosity,surface tension,nozzle spacing and different working fluids on the film formation of multiple jets are analyzed.Among them: as the jet velocity increases,the Reynolds shear stress amplitude at the same position will increase,but the Reynolds shear stress will attenuate to zero in the upper jet area;as the incident angle increases,the position of the upper jet appears will gradually move outward,the maximum height of the upper jet will gradually decrease;with the increase of the tension coefficient,the appearance position of the upper jet will gradually move inward,and the maximum height of the upper jet will gradually decrease;while the dynamic viscosity has an effect on the upper jet The zone has the same influence mechanism as the liquid accumulation zone,and the upward jet generated by high-viscosity fluid is higher;the liquid film that meets in the liquid film zone will cause splashing,while the liquid film that meets in the liquid accumulation zone is smoother;Compared with water,the liquid film formed by aviation kerosene is shorter and wider,and the liquid beam that it finally converges is also wider.