Numerical Simulation Of Jet And Flow Around Based On Gas Kinetic Scheme

Jet and flow are one of the important contents of fluid mechanics research,and they have a wide range of influences in the industrial field.Gas Kinetic Scheme can be applied to the entire basin,which is a hot topic of current research.In this paper,Gas Kinetic Scheme is used to study the applicability and flow field characteristics of jet and flow.GKS(Gas Kinetic Scheme,GKS)can set boundary conditions from both macro and micro perspectives.In this paper,several boundary conditions in GKS are constructed,such as Maxwell wall boundary condition,non-reflective boundary condition,etc.At the same time,Poiseuille flow and Couette flow are numerically simulated by using GKS.The velocity of flow field is compared with the steady analytical solution,and the accuracy of GKS algorithm is preliminarily verified.In this paper,a physical model suitable for simulating free jet is constructed.Through grid independence verification,the appropriate grid density is selected as the computational grid of the model.In order to verify the applicability of GKS in the free jet field,the numerical simulation results of GKS are compared with those of CFD and lattice Boltzmann methods,and the results are basically consistent.At the same time,the influence of Mach number on free jet flow field is studied.With the increase of Mach number,the farther the velocity goes downstream.At the same Mach number,as the jet distance increases,the jet width also increases.Two closely spaced opposed jets is simulated using GKS.By comparing the approximate analytical solution of two closely spaced opposed jets with the numerical results of GKS,the applicability of GKS algorithm in this field is verified.At the same time,the effects of nozzle spacing,nozzle velocity and nozzle gas velocity ratio on the axial and radial flow field characteristics is studied.As the nozzle spacing increases,the maximum radial velocity on the impinging face decreases,and the radial velocity increases first and then decreases with the radial distance.The nozzle velocity has little effect on the development of dimensionless radial velocity.The smaller the gas velocity ratio of the two nozzles,the larger the offset of the stagnation point on the impinging face.The flow around a single flat-plate,front and rear flat-plates,upper and lower flatplates and three flat-plates are numerically simulated by using GKS.The vorticity diagram and vortex diagram of the flat-plate flow at different Reynolds numbers are obtained.For a single flat-plate flow,with the increase of Reynolds number,the vortices behind the plate are continuously elongated and gradually lose their symmetry,resulting in the shedding of the vortices.For the front and rear flat-plate flow,there is no vortices when the distance between the plates is small,and vortices occur when the distance is large.For the upper and lower flat-plate flow,when the distance between the plates is small,it is equivalent to the single flat-plate flow.When the distance between the plates is large,the two rows of vortices gradually merge at a distance downstream.For the three flat-plates flow,vortices can still be formed when the upstream incoming flow is not uniform.