Study On Flow Field Characteristics Of Two-phase Flow Of Particles

The sedimentation of sediment in the water stream and the movement of dust and smoke in the atmosphere are all related to the problem of particle sedimentation.The study of particle sedimentation is of great significance to the cleanliness of the river,the collection and treatment of dust particle pollutants.In recent years,the main method used for the study of particle sedimentation is numerical simulation.However,using experimental methods to study the settlement of particles is a relatively intuitive and accurate research method.With respect to experimental research methods,Particle Image Velocimetry(PIV)is a full-flow,instantaneous,non-contact flow field testing technology.PIV technology is a combination of laser technology,digital signal processing technology,computer and image processing technology.It overcomes the limitations of single-point measurement and can test plane two-dimensional flow field,and it is an interference-free measurement technology.In this dissertation,the PIV experimental method was used to study the flow field characteristics of the particle sedimentation process,and the improved particle smoothing process was simulated using the Smooth Particle Hydrodynamics(SPH)numerical simulation method.The results of experiments and simulations were performed.Compared.The main works of the dissertation are as follows:(1)In this paper,particle image velocimetry was first used to verify the experiment,and the results were compared with the results of the numerical simulations of the scholars.The results are consistent,which proves the correctness and reliability of the experimental setup of this thesis.Then experiments were performed on the sedimentation of individual particles in the channel under gravity.Three kinds of particle release positions were set in the experiment to study the effect of different release positions on the particle sedimentation flow field characteristics under the same Re.At the same time,three different sets of Re were studied to study the process of sedimentation of different Re particles at the same position.The effect of the position and viscosity of the particles on the trajectory,velocity field and offset displacement of the particles was obtained through experiments.(2)Experiment on the sedimentation process of double particles.Three different settlement sites were set up in the experiment to study the effect of particle number on the flow field characteristics of the sedimentation process,and compared with the trajectory of individual particles during settling.It was concluded that in addition to the effect of wall effect on particles during sedimentation,The interaction between particles and particles has a greater influence on the sedimentation trajectory of the particles.During the experiment,the phenomenon of DKT in double particle sedimentation problems,namely dragging,kissing and tumbling,has appeared.(3)Simulate the above experiment by the improved SPH numerical simulation method.The improved SPH uses a new liquid-solid coupling model that eliminates numerical oscillations caused by differences in particle properties.At the same time,an improved coupled dynamic boundary processing method is used to improve the accuracy of boundary particle interpolation.The sedimentation process of the single particle at different positions and different Re and the different positions of the two particles was simulated.The simulation results of the settlement of the particles were in good agreement with the experimental results.