Velocity Field and Entrainment of a Pulsed Core Jet

Abstract

A pulsed core jet is one consisting of a steady annular flow with a core, the mass flow of which is unsteady. The combined jet exhausts into a still environment. The velocity field and entrainment characteristics for such a jet have been measured for various mass flow ratios of pulsed-to-steady flow and several frequencies of pulsation. Results show the radial distribution of mean velocity to be similar to those of steady jets except very close to the nozzle, the decay of the centerline mean velocity to be less than that of steady jets, and the entrainment to be larger than that of steady jets but less than fully pulsed ones. No significant sensitivity to frequency of pulsation was observed, but the velocity field is strongly dependent on the ratio of core flow to annular flow.