Time-domain simulation of acoustic sources over an impedance plane

An implicit high-order compact unconditionally stable finite-difference time-domain (FDTD) method is proposed here for numerical solution of point sources over an impedance plane. In this method, the linearized Euler equations are split into three directional sets and twelve simple wave components, or six when equivalent sources are adopted with no mean flow. Each component is solved using a fourth-order Padé approximant in space and second-order trapezoidal integration in time. The concept of reflection coefficient is used and algebraically modeled to develop time-domain impedance-equivalent boundary conditions. Comparisons with established methods for reflections of harmonic or impulsive sources demonstrate the applicability of this method for general impedance value, source type, or their arbitrary distributions. Examples of using typical wool felt and grass ground impedances are given to illustrate its practicality and effectiveness. This method provides a means through which time-domain theories and procedures for in-situ characterization of impedance surfaces can be developed.Department of Mechanical Engineerin