Particle Interaction Adaptivity and Absorbing Boundary Conditions in the Lagrangian Particle Aeroacoustic Model

Recently developed Lagrangian particle aeroacoustic model has shown its capability for simulating acoustic wave propagation problems in flowing fluids. It also has high potential for solving transient acoustics in a domain with moving boundaries. Typical application is sound wave propagation in continuous speech production. When the fluid flow or moving boundary is taken into account, initially evenly distributed particles will become irregular. For irregular particle distribution, the smoothed particle hydrodynamics (SPH) method with constant smoothing length suffers from low accuracy, phase error and instability problems. To tackle these problems, SPH with particle interaction adaptivity might be more efficient, with analog to mesh-based methods with adaptive grids. When the wave arrives at the open boundary, absorbing conditions have also to be applied. Therefore, the main task of this work is to incorporate variable smoothing length and absorbing boundary conditions into the Lagrangian particle aeroacoustic model. The extended model is successfully validated against three typical one- and two-dimensional sound wave propagation problems.