Simulation Of Horizontal Gas-Solid Two-Phase Flows

Horizontal gas-solid flows are common in nature and have important applications in industry.Although gas-solid systems have been studied for many years,the understanding of this systems is not comprehensive.With the development of computing power,computational fluid dynamic method has been widely used in recent years.The Multiphase Particle-In-Cell(MP-PIC)method is adopted in this thesis because of its high accuracy and efficiency.To further understand the gas-solid system,the process of gas-solid flows in a horizontal pipe and near space were simulated based on the MP-PIC method.The main contents are as follows:To verify the accuracy of MP-PIC method and gas-soild theories,the siluation result of gas-solid dilute penoumatic conveying in a horizontal pipe was compared with experimental measurement.The simulation results showed collisions between particles and pipe wall has significant influence on result.Therefore,finding the proper value of the momentum retention parameters is important for collision model.Comparing the results of different drag models,it was found that the velocity distribution of gas and particles was more accurtae when the drag force is larger,which further implies developing drag force model for horizontal gas-solid system is necessary.In addition,turbulence modulation model was added to the standard k-ε turbulence model to take into account the influence of particles on gas turbulence.The results showed that the k-ε model with turbulence modulation can only predict the trend of gas turbulence distribution,and there was noticeable discrepancy between simulation result and experimental data.The accuracy of gas fluctuating velocity was improved when the slip velocity term was ignored in the source term of turbulence modulation.To simulate the particles movement in near space,this thesis firstly verified the reliability of the computational fluid dynamic method based on continuous hypothesis in near space.It also provided a reference for selection of particle in the experiment.The simulation result of particles empting process from the column provided the inlet velocity of particles,not only the vertical velocity but also the horizontal velocity generated due to the collision during the emptying.On this basis,the particles release process in near space was simulated.The simulation result showd that the average velocity o f the particles in the horizontal direction was getting close to the wind velocity So the detailed characteristics of wind field in the near space can be obtained by measuring particles velocity.The simulation results demonstrate the feasibility of the experiment scheme and provides a reference for the subsequent experiment design.