Automated design optimization of a three-dimensional S-shaped subsonic diffuser

Sophia Lefantzi, Doyle D. Knight

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


An automated design optimization process for subsonic S-shaped diffusers was developed and validated. The test case for the process was the evolution of an optimal design for an S-shaped subsonic diffuser, where optimality was based on the minimization of the total pressure distortion at the diffuser exit, while sustaining total pressure recovery. Constraints placed by airframe weight, space, and line-of-sight blockage of the engine face cause subsonic diffusers to be highly divergent and curved, characteristics that lead to strong secondary flows, boundary-layer separation, and inhomogeneity of the total pressure profile. As a part of the design process, we introduce a surface perturbation (bump) on a baseline S-shaped diffuser, and minimize an objective function, reflecting the total-pressure distortion, with respect to the perturbation height and width. To synthesize the automated analysis and optimization method, we created a Subsonic Diffuser Design System (SDDS), which utilizes four commercial/third-party software tools. These tools are Pro/Engineer (a three-dimensional solid modeler for the generation of diffuser geometries), GridPro (an elliptic mesh generator), GASPex (an aerodynamic simulation package), and CFSQP (a gradient-based optimizer to traverse the design space automatically). The integration of Pro/Engineer significantly expands the capability of SDDS to enable multidisciplinary design, for example, include structural and thermal analysis, into the automated design process. Results indicate the development of the surface perturbation and a consequent decrease in total pressure distortion during the convergence to the optimal geometry. We emphasized on the flowfield visualization of the optimal diffuser and detected a complex three-dimensional separation region inside the bump.

Original languageEnglish (US)
Pages (from-to)913-921
Number of pages9
JournalJournal of Propulsion and Power
Issue number4
StatePublished - 2002

All Science Journal Classification (ASJC) codes

  • Aerospace Engineering
  • Fuel Technology
  • Mechanical Engineering
  • Space and Planetary Science


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