Research On SPH And Multiscale Method For The Simulation Of Chemical Separation Flows

A new micro-separation device called "micro-filter" with high separation efficiency was investigated in this study in order to improve the low productive efficiency, high pollution and high energy consumption in the separation and purification of the chiral drug and some protein compounds. The micro-filter constructed by the micro-channels etched on the silicon and quartz substrate was fabricated by the microfluidics technology. The micro-channels were optimization designed to make the different components of the composite have different transport velocities in the flow path so that a high separation flux would got. Because of the rarefied feature caused by the small characteristic length scales, the traditional CFD methods based on the Euler or the Navier-Stokes equations can't be used.A proper multiscale simulations method was studied in this paper in order to predict the flow characters in the micro-filter. In the simulation many complicated phenomena will be encountered, for example, there would be both continuum and rarefied flows in the devices and the flows are often combined by the electromagnet effects. So a hybrid method was proposed in this paper in which the rarefied flows were simulated by direct simulation Monte Carlo (DSMC) method while the continuum flows were treated by smoothed particle hydrodynamics (SPH) method. The two methods are both particle based methods and simulate the flows physically, so they can be used conveniently to simulate the complicated flows in the micro-filter.In this paper, the basic ideas of the two methods and the governing equations were outlined when simulating the continuum and rarefied flows. Then the coupling of the two approaches was described in detail. In order to provide the validation of the methods, the programs based on these theories were written by FORTRAN language. The numerical simulations carried out by SPH programs were shown here. Firstly, to demonstrate the validity of the method, Couette and Poiseuille flows were simulated using the program and the results had shown close agreement with series solutions. During the calculation the results got by quintic spline kernel was the best so it was chosen as the proper kernel for the SPH simulation. By comparison of the simulationresults got by SPH and finite volume method, it was proved that the buffer cells method proposed in the SPH simulation to implement the Dirichlet boundary conditions was accurate, and this is of great importance for the simulation of flows pass a pipe. At last, the SPH method was improved to simulate the liquid-solid two phase flows and the results show that this method was appropriate for the simulation of flows containing viscous fluid and macroscopic solid components. Now the two methods are both able to predict the continuum flows and rarefied flows severally, but the hybrid program still has some aspects to be improved. The tasks need to done in the future research are outlined in the sum-up and prospect.