Automated Design of a Three-Dimensional Subsonic Diffuser

Abstract

A novel methodology is developed to integrate state-of-the-art computational e uid dynamics analysis, NURBS, and optimization theory to reduce total pressure distortion and sustain total pressure recovery within a curved three-dimensional subsonic S-duct diffuser by automated redesign of the diffuser shape. Two independent design variables are used. The change of the surface shape is assumed to be Gaussian. GASP with the modie ed Baldwin ‐ Lomax turbulence model (Baldwin, B. S., and Lomax, H., “ Thin Layer Approximation and Algebraic Model for Separated Turbulent Flows,” AIAA Paper78-257, 1978 )is employed for the e owe eld prediction and proved to give good agreement with the experimental surface pressure for the baseline S-duct diffuser geometry. The automated design optimization is performed with a gradient-based method to minimize the total pressure distortion based on the two design variables. The best cone guration obtained reduced distortion by typically 70% while keeping the total recovery essentially the same. The results indicate that the mechanism responsible for improved diffuser performance is the suppression of detrimental secondary e ows by changing the surface shape to redirect the e ow.