T.Y. Li

Smoothed particle hydrodynamics approach for modeling sound of a rigid body falling on water

Computational acoustic methods based on Eulerian description are widely used in industrial applications. However, some special acoustic problems, such as transient acoustic problems with moving or deformable boundaries, object separation, or for multiphase systems, are still cannot ideally solved with these Eulerian methods. The present work aims at using a Lagrangian meshfree method, the smoothed particle hydrodynamics (SPH), to simulate a time-domain acoustic problems with moving boundaries which is the sound of a rigid body falling on water. First, Lagrangian acoustic wave equations considering the sound source based on the hydrodynamic/acoustic splitting method are given and represented in the SPH form. Then, two-dimensional simulation of a rigid object falling on the free surface of water is computed by the SPH method. Noise sources are obtained from the flow field information of each fluid particle. Finally, acoustic experiments with measuring the sound of the rigid body falling on water are used to...

Smoothed particle hydrodynamics simulation of sound reflection and transmission

Meshfree methods are widely used in computational acoustics to solve complicated domain topologies and multiphase systems. Smoothed particle hydrodynamics (SPH) is a Lagrangian meshfree method that offers the advantages of meshfree technology and Lagrangian property. The present work simulates the sound reflection and transmission of sound waves in multiple media in the time domain with the SPH method. First, acoustic wave equations in a quiescent fluid are represented in SPH form using particle approximation. A reflecting Dirichlet boundary condition is then built with the dummy particle technique. One-dimensional sound reflection and transmission are finally simulated with the meshfree SPH method, and the solutions are compared with theoretical results. The errors of sound pressure show that the SPH method is feasible in simulating the reflection and transmission of sound waves in the time domain. The boundary works well with plane waves. The change in sound speed obtained from the SPH simulation of aco...

Lagrangian meshfree particle method for modeling acoustic wave propagation in moving fluid

Introducing the Lagrangian approach to acoustic simulation is supposed to reduce the difficulty in solving problems with deformable boundaries, complex topologies, or multiphase media. Specific examples are sound generation in the vocal track and bubble acoustics. As a Lagrangian meshfree particle method, the traditional smoothed particle hydrodynamics (SPH) method has been applied in acoustic computation but in a quiescent medium. This study presents two Lagrangian approaches for modeling sound propagation in moving fluid. In the first approach, which can be regarded as a direct numerical simulation method, both standard SPH and the corrective smoothed particle method (CSPM) are utilized to solve the fluid dynamic equations and obtain pressure change directly. In the second approach, both SPH and CSPM are used to solve the Lagrangian acoustic perturbation equations; the particle motion and the acoustic perturbation are separated and controlled by two sets of governing equations. Subsequently, sound propa...

Computation of nonlinear acoustic waves using smoothed particle hydrodynamics

A Lagrangian approach for solving nonlinear acoustic wave problems is presented with direct computation from smoothed particle hydrodynamics. The traditional smoothed particle hydrodynamics method has been applied to solve linear acoustic wave propagations. However, nonlinear acoustic problems are common in medical ultrasonography, sonic boom research, and acoustic levitation. Smoothed particle hydrodynamics is a Lagrangian meshfree particle method that shows advantages in modeling nonlinear phenomena, such as the shock tube problem, and other nonlinear problems with material separation or deformable boundaries. The method is used to solve the governing equations of fluid dynamics for simulating nonlinear acoustics. The present work also tests the method in solving the nonlinear simple wave equation based on Burgers’ equation. Effects of initial particle spacing, kernel length, and time step are then discussed based on the wave propagation simulation. Different kernel functions are also evaluated. The res...