Direct Simulation Of Sound Propagation In Ducts Based On Lattice Boltzmann Method

The problem of sound propagation in ducts has always been a classical problem in the field of acoustics research,and also has a wide range of applications in the engineering field.For example,it is essential to measure acoustic parameters such as the absorption coefficient of materials,to reduce the strong noise hazards caused by equipment such as gas turbines and jet devices,and even to ensure the acoustic concealment safety of submarine underwater navigation.The Lattice Boltzmann Method(LBM),as a new method for fluid modeling and solution,can reduce to the Navier-Stokes system of equations under microcompressible conditions,and has the characteristics of easy boundary handling,low dispersion and low dissipation,which is very suitable for the simulation of the acoustic field.In this paper,LBM and LBM-based fluid-structure coupling model are used to directly simulate the sound propagation problem in a rigid-walled duct and in an elastic-walled duct with fluid-structure coupling effect.In the first part of this paper,we focus on the direct simulation of problems related to sound propagation in rigid-walled ducts using LBM.The applicability of two common boundary conditions in LBM to this problem is first verified.Then the LBM are used to directly simulate the sound propagation problem in a two-dimensional rigid-walled duct.The numerical solution basically matches the theoretical solution,which verifies the effectiveness of the LBM for direct simulation of sound propagation in ducts.Subsequently,the classical physical phenomena of sound propagation in a rigid-walled duct,such as standing waves and cutoff frequencies in the pipe,are reproduced.The second part of this paper focuses on the direct simulation of problems related to sound propagation in elastic-walled ducts using an LBM-based fluid-structure coupling model.Firstly,the important theoretical and algorithmic solution procedure in the fluidstructure coupling model is introduced.Subsequently,the model is used to directly simulate the sound propagation problem inside a two-dimensional approximate rigid-walled duct,and the numerical results basically match with the theoretical values,which verifies the feasibility of the coupled model for solving the sound propagation problem inside elastic-walled ducts.Finally,the effects of Young’s modulus,incident wave wavelength and fluid medium on the sound propagation loss in the elastic wall duct are investigated.The numerical results show that the Young’s modulus of the elastic wall material will produce a certain "resonance" with the incident wave near a specific value,and in the air medium,the resonance of the elastic wall appears The Young’s modulus of the material is much smaller than that in the aqueous medium when "resonance" occurs.