Time-Domain Impedance Boundary Conditions with Mean Flow Effects

The development of time-domain impedance boundary condition (TDIBC) for prediction of aeroacoustics in wall bounded flows is explored. The presence of a flow and its boundary layer over a wave-absorbing surface com- plicates the modeling and implementation of TDIBC. Considered here are three different approaches to account for the effects of wave refraction, absorption, reflection, and convection at a wave-absorbing wall. They are the effective plane-wave impedance in a slip flow, convection-modified impedance in a slip flow, and wave reflection in a mean shear-layer flow. Their validity, effectiveness, stability, and implementation in time-domain finite-difference schemes will be discussed. The schemes and methods developed here are benchmarked and compared with experiment and other methods.