A Study Of Sound Propagation Under Moving Boundary Conditions Using SPH Simulation

Changes of vocal tract shape often occur in continuous speech production.It is of high importance to explore acoustic propagation problems in the tube with boundary movement.At present,a variety of numerical methods have been widely used in computational acoustics.Based on discrete forms of the governing equations,numerical methods are divided into two types: mesh-based methods and meshless methods.Meshless methods use particles to discretize the space domain,which avoids the loss of accuracy caused by mesh reconstruction or distortion when the traditional meshbased methods are used to deal with transient or large deformation problems.Meanwhile,meshless methods have achieved remarkable success in many fields(such as astrophysics,fluid mechanics,etc.).Thus,in this paper the smoothed particle hydrodynamics(SPH)method,a typical meshless method,is adopt for solving Euler equations to simulate sound wave propagation in human vocal tract with focus on the treatments of the boundary.To validate the developed solver,the flow separation in right angle elbow and fountain are simulated.The treatments of wall boundary,inlet and outlet boundary are also described in detail.The experimental results show that the treatment of inlet boundary based on the extrapolation is better than that of other inlet boundary treatment methods.The density smoothing method can be applied to get a stable numerical results.The numerical results show that this method is valuable for boundary treatment.In terms of computational acoustics,this paper simulates the problems of sound wave propagation in 1-D and 2-D tubes.It is shows that perfectly matched layer(PML)has good performance as absorbing boundary.At the same time,the resonant frequency of the acoustic wave in a two-dimensional tube is investigated under the open / close conditions at its right side.The experimental results show that the frequency values of the numerical results are consistent with the theoretical values.In addition,sound propagation under the moving vocal tract is simulated,which provides a good reference for the simulation of sound wave propagation in human vocal tract.