No abstract

Experimental data of the peak axial-velocity decay in a moving airstream are presented for several types of nozzles. The nozzles include a six-tube mixer nozzle of a type considered for reduction of jet-flap interaction noise for externally-blown-flap STOL aircraft. The effect of secondary flow on the core flow velocity decay of a bypass nozzle is also discussed. Tentative correlation equations are suggested for the configurations evaluated. Recommendations for minimizing forward velocity effects on velocity decay and jet-flap interaction noise are made.

A b s t r a c t A modeling technique for p r e d i c t i n g t h e a x i a l and t r a n s v e r s e v e l o c i t y c h a r a c t e r i s t i c s o f rectangul a r nozzle plumes i s developed. I n t h i s technique, modeling o f t h e plume cross s e c t i o n i s i n i t i a t e d a t the n o z z l e e x i t plane. The technique i s demons t r a t e d for t h e j e t plume i s s u i n g fr0m.a r e c t a n g u l a r n o z z l e having an aspect r a t i o o f 6.0 and dischargi n g i n t o q u i e s c e n t a i r . The j e t i s assumed to be subsonic and o p e r a t i n g w i t h c o l d flow. A p p l i c a t i o n of the present procedures t o a nozzle d i s c h a r g i n g i n t o a moving a i r s t r e a m ( f l i g h t e f f e c t ) a r e then demonstrated. F i n a l l y , the e f f e c t s o f plume shear l a y e r s t r u c t u r e m o d i f i c a t i o n on t h e v e l o c i t y flowf i e l d a r e discussed and modeling procedures a r e i l l u s t r a t e d by example. While some aspects of t h e p r e s e n t modeling procedure may r e q u i r e some f u r t h e r experimental v e r i f i c a t i o n , the trends and general magnitudes o f t h e several e f f e c t s i n c l u d e d i n t h e study a r e considered a p p r o p r i a t e and r e a l i s t i c . t i o n f u n c t i o n s d e f i n e d i n t e x tr e c t a n g u l a r n o z z l e major a x i s r e c t a n g u l a r n o z z l e or plume h e i g h t ( s h o r t ) dimensions f r o m c e n t e r l i n e a c o u s t i c e x c i t a t i o n l e v e l Mach number s u p e r e l l i p t i c plume cross s e c t i o n exponent c i r c u l a r n o z z l e or plume r a d i u s e x c i t a t i o n Strouhal number t o t a l temperature s t a t i c temperature v e l o c i t y r e c t a n g u l a r n o z z l e major a x i s r e c t a n g u l a r n o z z l e or plume w i d t h ( l o n g ) dimension from c e n t e r l i n e a x i a l d i s t a n c e from nozzle e x i t plane core l e n g t h g e n e r i c n o z z l e or plume dimension c i r c u l a r plume cross s e c t i o n c o r e conventional d e p a r t u r e p o i n t f l i g h t , f r e e s t r e a m n o z z l e or plume h e i g h t d i r e c t i o n j e t e x i t m i xed s t r u c t u r a l l y modified plume shear l a y e r n o z z l e r a d i u s , r a d i a l s t a t i c s t a t i c temperature t o t a l t r a n s i t i o n n o z z l e or plume w i d t h d i r e c t i o n t r a n s v e r s e dimension a t end o f core g e n e r i c dimension or d i r e c t i o n h a l f -v e l o c i t y contour S u p e r s c r i p t s :t r a n s v e r s e d i s t a n c e measured from plume core boundary or c e n t e r l i n e (downstream o f XC) I n t r o d u c t i o nFuture h i g h speed commercial t r a n s p o r t (HSCT) a i r c r a f t a r e l i k e l y t o use asymmetric exhaust nozz l e s i n o r d e r t o p r o v i d e enhanced j e t n o i s e reduct i o n c a p a b i l i t y and t h e r e b y meet s t r i n g e n t FAA n o i s e r e g u l a t i o n s , p r e s e n t and f u t u r e . Compared t o c i r...

No abstract

No abstract