Acoustic and entropy wave input–output relationships for quasi-one-dimensional gas flows

Abstract

The transmission, reflection, and interaction of linear, one-dimensional acoustic and entropy waves within subsonic, quasi-one-dimensional, finite length gas flows is considered. A numerical analysis is used to relate the time variations in gas properties along the length of the duct. Appropriate equations are derived for the case of a nonviscous, nonheat-conducting, fixed composition, ideal gas with constant specific heats and no external body forces or energy sources, though the general procedure may be applied to more complicated flows. The results are expressed in terms of nine frequency-dependent reflection and transmission coefficients. To demonstrate the analysis, calculations are presented for a 4:1 area ratio, 1-m-length nozzle and for a 1:4 area ratio, 1-m-length diffuser.