Effects of radial blowing on the spreading characteristics of axisymmetric jets

Abstract

The spreading characteristics of circular jets at Mach number 0.8 (Re D=230 000) and 1.5 (ReD=430 000), are manipulated by radial jets located at different locations and combinations. The number of radial jets used in this study ranges from 1 to 4 and the blowing ratio spans from 0.65 to about 3 percent of the mass flow of the primary jet. The stagnation pressures of the radial jets are set small so that only the cases where minimal amount in the expenditure of energy is considered. The current study shows that application of radial jets in a high subsonic flow improve the mixing of the jet by reducing the potential core length of up to three jet diameters. The study also shows that while the number of radial jets affect the extent of the mixing enhancement; the positioning of the radial jets is also important. For the same blowing ratio and similar blowing locations to an underexpanded supersonic jet, the primary jet becomes more stable and mixing is reduced. While undoubtedly a high enough back pressure of the radial jets will destabilize the supersonic primary jet, studies at higher pressures are not considered here.