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Cwved Ducts and Comparison With r~d s i u~-a 3 5 4 a ) C O U P U T A T I G Y or VISCOVS PLOY 184-13494 I Y CU Vi3D DUCTS B l i D C(3LIPABlSOY d1THb EXPERA three-dimensional analysis f o r f u l l y viscous subsonic i n t e r n a l f l o w i s evaluated. The andlysis, designated PEPSIG, solves an approximate f o r m o f t h e Navier-Stokes equations by an i m p l i c i t s p a t i a l marching procedure. Results o f calculations are presented f o r laminar flow through two d i f f e r e n t c i r c u l a r cross-sectioned 180 degree bends, and f o r laminar and turbulent f l o w through c i r c u l a r and square cross-sectioned 22.5-22.5 degree S-ducts. comparisons w i t h experimen a1 data are shown f o r a l l cases. i s placed on v e r i f y i n g the a b i l i t y o f t h e analysis t o accurately p r e d i c t t h e d i s t o r t e d f l o w f i e l d s resu t i n g from pressure-driven secondary flows. Q u a n t i t a t i v e Special emphasis INTRODUCTIONThe presence of three-dimensional subsonic i n t e r n a l f l o w i s r e l a t i v e l y comnon i n many o f today's airbreathinq propulsion systems. Curved center1 ines and changes i n cross-sectional shape are o f t e n present, r e s u l t i n g i n the gene r a t i o n of complex three-dimensional secondary flows and s i g n i f i c a n t f l o w dist o r t i o n . layer thickness o f t e n comparable t o ?he duct radius. These phenomena have important effects on ovel-all p r o p u l s i c i system performance.I n addition, viscous e f f e c t s are u s u a l i y important, w i t h the boundary Conventional boundary layer methods w i l l not work f o r these complex flows. A f u l l Navier-Stokes s o l u t i o n could be used, b u t would r e q u i r e l a r g e amounts o f computer time and storage. However, by making c e r t a i n approximations t o t h e Navier-Stokes equations, such as 'ieglecting streamwise d i f f u s i o n , a set o f equations can be derived for f u l l y viscous i n t e r n a l f l o w t h a t can be solved b y forward marching i n space. An analysis method using tnese equations t o compute three-dimensional subsonic f l o w through curved ducts w i t h s u p e r -e l l i p t i c crosssections was developed by B r i l e y and McDonald ( r e f . 1) and by Levy, McDonald, B r i l e y , and Kreskovsky ( r e f . 2), and was designated PEPSIG. A preliminary evaluation o f the PEPSIG method was presented by Towne and Anderson ( r e f . 3). However, i n t h a t evaluation o c l y q u a l i t a t ' v e comparisons were made w i t h data. I n addition, ;ever81 changes have since been made t o the analysis by Levy, B r i l e y , and Mcr)onA.ld ( r e f . 4).The objective o f the present study, therefore, was t o evaluate and v e r i f y the most recant version o f the PEPSIG analysis by making d e t a i l e d q u a n t i t a t i v e comparisons between predicted r e s u l t s and benchmark experimental data. Special emphasis was clirced on t e s t i n g the a b i l i t y of the analysis t o accurately w ed i c t the d i s t o r t e d t...

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