Paper 10: Unsteady Flow in a Branched Duct

Abstract

The results of an investigation into the behaviour of a finite amplitude pressure wave at the junction formed by the intersection of two ducts of equal cross-sectional area are presented. Using a shock tube to produce waves with amplitudes varying from 1 to 37 lb/in2 (g), pressure measurements were made in three junctions in which the side branch formed an angle of 45, 90, and 135° with the main branch. The results are compared with a theoretical analysis which is based on the assumption of one-dimensional, quasi-steady, adiabatic flow. Differences in the theoretical and experimental values have been found at the junction entrance when the velocity at the entrance is subsonic and in the side branch when the velocity at the entrance is sonic. These differences are explained in terms of the wave action known to occur within the junction.