Physics of Coanda jet detachment at highpressure ratio
Abstract
Experimental measurements of surface pressure for an underexpanded twodimensional supersonic Coanda flow with static conditions exterior to the jet flow was obtained for a fixed slot height to a radius ratio of 0.04. The data demonstrate that an oblique shock forms near the jet exit plane which vectors the jet flow from the curved surface at a pressure ratio of 7.6. The jet detachment occurs at a pressure ratio which is a function of the ratio of slot height to cylinder radius. An increase in the pressure ratio to 11.5 before jet detachment has been demonstrated by the translation of the upper wall providing for a convergingdiverging geometry. The physics of the Coanda expansion and the jet detachment are qualitatively described using an optical schlieren system. A compressible inviscid model was derived analytically to demonstrate the variation in Mach number and surface pressure as a function of the geometric parameters with increasing pressure ratio.
 Publication:

Journal of Aircraft
 Pub Date:
 May 1994
 Bibcode:
 1994JAir...31..591C
 Keywords:

 Coanda Effect;
 Jet Flow;
 Pressure Ratio;
 Supersonic Flow;
 Two Dimensional Flow;
 ConvergentDivergent Nozzles;
 Inviscid Flow;
 Mach Number;
 Oblique Shock Waves;
 Separated Flow;
 Slots;
 Fluid Mechanics and Heat Transfer