Simulation Of Fluid Flow And Acoustic Based On MRT-LBM

The LBM is a kind of mesoscopic numerical analysis method,which has not only the characteristics of microscopic methods,but also the advantage of molecular motion.So it has great superiority and potential in the analysis of complicated flow problems of multi-scale and multi-physics.From a computational perspective,the physical evolution of LBM is clear and easy to program.Meanwhile the computation is local and it has natural parallelism.So calculation of large-scale flow problem has a great advantage.Compared with the BGK model which has only one relaxation time,the MRT model which has multiple relaxation time has better stability.In this paper,the MRT-LBM is designed from the theory to the program,and then the program is implemented by Matlab language.For the simulation of the flow field,the main work includes two aspects.Firstly,the flow field simulation and results analysis of the two-dimensional rectangular cavity with different aspect ratios are carried out by setting Reynolds number from 40 to 200.Then the effects of flow which has Reynolds number 40 or 200 under different rotating speed of the cylindrical two-dimensional pipe are studied.The two kinds of Reynolds number are corresponding to steady and unsteady conditions.Then we quantitatively describe the relationship of speed change ratio and lift coefficient and drag coefficient.For the simulation of acoustics,the simulation of one-dimensional plane wave attenuation is carried out.Then,the diffraction and interference phenomena of the acoustic wave are simulated by the plane wave slit transmission experiment,which shows that the LBM can describe the basic characteristics of the acoustic wave.Thirdly,with the simulation of point source propagation in steady flow,the Doppler effect is reproduced,which shows that the LBM has the ability to simulate the interaction between flow and acoustic wave.Finally,the LBM simulation of point sound source under free space through the slit attenuation is carried out.By setting different wavelength?slit length? slit width and slit number we get the relationship between the related parameters and the sound pressure.