Copyright ©1996, American Institute of Aeronautics and Astronautics, Inc. AIAA Meeting Papers on Disc, May 1996 A9630781, NAG1-1367, AIAA Paper 96-1663 A time-domain implementation of surface acoustic impedance condition with and without flow Yusuf Ozyoruk Pennsylvania State Univ. University Park Lyle N. Long Pennsylvania State Univ. University Park AIAA and CEAS, Aeroacoustics Conference, 2nd, State College, PA, May 6-8, 1996 The impedance condition in computational aeroacoustic applications is required in order to model acoustically treated walls. The application of this condition in time-domain methods, however, is extremely difficult because of the convolutions involved. In this paper, a time-domain method is developed which overcomes the computational difficulties associated with these convolutions. This method builds on the z-transform from control and signal processing theory and the z-domain model of the impedance. The idea of using the z-domain operations originates from the computational electromagnetics community. When the impedance is expressed in the z-domain with a rational function, the inverse z-transform of the impedance condition results in only infinite impulse response type, digital, recursive filter operations. These operations, unlike convolutions, require only limited past-time knowledge of the acoustic pressures and velocities on the surface. One- and two-dimensional example problems with and without flow indicate that the method promises success for aeroacoustic applications. (Author) Page 1