Sound Generation by Low Mach Number Flow Through Pipes with Diaphragm Orifices

Kurzfassung

Aerodynamic noise generated by low Mach number flow through a pipe with two differently sized diaphragm orifices is investigated both theoreti-cally as well as numerically. Such a flow may be considered as a simple model of an aircraft climate control system. The theory is based on an acoustic analogy introduced by Möhring and Ober-meier in the seventies. They identified by means of the so-called Green`s vector function acoustic sources in unsteady flows as the unsteady motion of vorticity “vortices are the voice of flows”. In addition, the unsteady flow through the pipe, the aerodynamic sources, and the spectra of sound are evaluated numerically. Here effects of different numerical algorithms (PISO – PIMPLE) and of different numerical boundary condi-tions at the outlet of the pipe (advective, convective – wave transmissive) are identified and discussed.