Lattice Boltzmann Simulation Of Fluid Flow Characteristics In Rectangular Microchannels

With the widespread application and miniaturization of microelectromechanical systems(MEMS)devices,the in-depth study of micro-scale flow problems has become a new hot spot in the field of fluid mechanics research.The research results will significantly promote the development of fluid mechanics theory.In this paper,a mesoscopic simulation method based on the assumption of discontinuity lattice Boltzmann method(LBM)is employed to simulate the flow characteristics of three-dimensional developing laminar flow in rectangular microchannels.It has many advantages,such as a clear physical background,easily handling the boundary conditions and simple calculation procedures.According to the basic theory of the lattice Boltzmann method,we established a three dimensional lattice Boltzmann model considering rarefaction effects and aspect ratios.In this paper,three-dimensional simulation procedures of lattice Boltzmann method are written in a Fortran language.For continuous flow and Poiseuille flow,the standard LBM model is employed to simulate to verify the feasibility of LBM and the credibility of the procedure.For the simulation of microchannel flow in slip regime,we must give appropriately the relationship between the relaxation time ? and Knudsen number and consider a combination of bounce and specular reflection to characterize the phenomenon of boundary slip.The modified LBM model is used to study the velocity development and boundary slip in the entrance region of microchannels,and the effects of aspect ratios and Knudsen number on the flow resistance along the microchannels are also studied.Comparison of the simulation results with the semi-theoretical solution and the results of traditional calculation method yields a great agreement.It is demonstrated that using the modified model to investigate the flow characteristics of microchannels in slip regime is reasonable.The results of this paper can predict distribution characteristics of the friction and pressure drop of continuous flow and slip flow in the entrance region for rectangular microchannels.The present study provides a basis for further academic research in the future,and it is convenient for the engineering practice and application.In a word,we have conducted a systematically and detailedly numerical study on the flow characteristics of the micro-channel entrance region by using the lattice Boltzmann method,which provides a way of future research on the fluid flow characteristics in the transition region.