Time-domain numerical simulation of a flow-impedance tube

An efficient method has been developed for. the application of the surface acoustic impedance condition in time-domain solutions of aeroacoustic problems, such as the broadband-frequency simulation of a flow-impedance tube, The basis for this method is the standard impedance condition stated in the frequency domain as the particle displacement continuity equation. The development of the time-domain impedance condition follows the relations among the frequency. z-, and discrete-time domains and a rational function representation of the impedance in the z-domain. The resultant impedance condition consists of finite, infinite-impulse-response type, digital filter operations in the time domain, which is very suitable to computational aeroacoustics algorithms. This paper describes the present approach and discusses the time-domain numerical simulations of the NASA Langley how-impedance tube with a constant depth ceramic tubular liner. Both single and broadband-frequency simulations are performed. Excellent agreement is shown with experimental data at various frequencies and flow conditions. (C) 1998 Academic Press.