Effects of tangential blowing on high-speed jets

Abstract

Velocity measurements have been performed to survey the effect of tangential blowing to enhance the mixing of jets. Mixing enhancement was expected to result from the creation of stream wise vorticity and from the effect of centrifugal forces. The velocity field in the plume of Mach 0.8 and 1.5 jets was measured with a Pitot rake. In the subsonic case, tangential blowing from two diametrically opposite ports enhances the jet mixing and reduces by 67% the length of the potential core. This requires an actuation mass flow rate less than 1 percent of that of the main jet. Significant deformation of the plume cross section is observed which suggests the induction of streamwise vortices entraining and mixing ambient air. Flow visualization techniques can reveal this phenomenon. Centrifugal forces seem to play a minor role since the tangential blowing induces a mild swirl in the jet. Tangential blowing was less effective in the supersonic case, possibly the result of inducing a striction of the jet potential core in the axial direction.