REDUCTION OF PLUME SIGNATURE FROM RECTANGULAR NOZZLES BY NOZZLE DESIGN FOR VORTICITY MANIPULATION

THE USE OF RECTANGULAR EXHAUST NOZZLES FOR AIRCRAFT CONFIGURATIONS OFFERS SOME INTERESTING POSSIBILITIES IN THE AREA OF FLOW MANIPULATION IN ORDER TO ENHANCE THE MIXING OF THE HOT EXHAUST PLUME WITH THE SURROUNDING COOL AIR. THIS PROPOSAL SUGGESTS THAT THE MANIPULATION AND PLACEMENT OF STREAMWISE VORTICITY IN THE FLOWFIELD WILL SERVE TO SIGNIFICANTLY INCREASE THE MIXING OF THE EXHAUST PLUMES. THE PLACEMENT OF VORTICITY HAS BEEN DEMONSTRATED AND MAY BE ACCOMPLISHED THROUGH SEVERAL MEANS. STREAMWISE VORTICITY RESULTING FROM RESIDUAL SWIRL CREATED BY THE ENGINE TURBOMACHINERY, THROUGH THE USE OF NOZZLE WALL CONTOURING, MAY BE PLACED IN SUCH A WAY AS TO CREATE WELL DEFINED STREAMWISE VORTICES. MODIFICATION OF THE FINAL TURBINE STATOR BLADE ROW MAY BE USED TO PLACE STREAMWISE VORTICITY IN THE EXHAUST PLUME. FINALLY, FORCING THE SEPARATION OF THE BOUNDARY LAYER WHICH FORMS ON THE NOZZLE WALL MAY BE USED TO MANIPULATE EXISTING VORTICITY IN THE FLOW TO CREATE AXIAL VORTICES. THE GOAL OF THE WORK PROPOSED, UNDER PHASE I, IS TO DETERMINE WHICH PATTERNS OF STREAMWISE VORTICITY WILL BEST SERVE TO ENHANCE THE PLUME MIXING AND TO PROPOSE NOZZLE GEOMETRIES WHICH WILL CREATE THESE VORTEX PATTERNS.