Computational Analysis on Flow Through Transition s-Diffusers: Effect of Inlet Shape

TLDR

Diffusing transition S‑ducts are widely used in dual‑engine fighter aircraft intakes, and the inlet cross‑section shape significantly affects duct performance. The study establishes computational fluid dynamics as a design tool for intake design. The authors evaluated elliptic, semicircular, oval, rectangular, and square inlet shapes using standard and renormalized group k‑turbulence models at 0.17 Mach with fixed geometry parameters. Elliptic inlet shapes achieved the best pressure recovery, lowest loss coefficient, and minimal flow distortion, while square shapes performed worst, and the renormalized group k‑turbulence model outperformed the standard model.

Abstract

DOI: 10.2514/1.22828 Diffusing transition S-ducts are often used in dual engine fighter aircrafts as intake ducts. The cross section shape at the inlet of the intake duct affects the performance of the duct. The present paper establishes computational fluid dynamics as a design tool for intake design. Various cross section shapes of the inlet, namely, elliptic, semicircular, oval, rectangular, and square, have been analyzed using the standard and the renormalized group k– turbulence model. For all the ducts, the angle of turn (22:5=22:5 deg), the centerline length (300 mm) and the circular exit diameter(100mm)havebeenkeptconstant.Incompressible flowanalysishasbeendoneat0.17Machnumberatthe entry of the duct which corresponds to the throat of intakes. The elliptic-shaped inlet duct shows the best performance in terms of pressure recovery, loss coefficient, and flow distortion at the compressor face, whereas square duct produces the worst flow characteristics. It is also established that the renormalized group k– model predicts better than the standard k– turbulence model.