Simulation of Secondary and Separated Flow in Diffusing S Ducts

Abstract

The focus of this paper is on the numerical simulation of compressible flow in diffusing S-ducts; this flow is characterized by secondary flow as well as regions of boundary-layer separation. The S-duct geometry produces streamline curvature and an adverse pressure gradient resulting in these flow characteristics. Two S-duct geometries are employed in this investigation: one was used in an experimental study conducted at NASA John H. Glenn Research Center at Lewis Field in the early 1990s, and the other is a benchmark configuration proposed by AIAA Propulsion Aerodynamics Workshop to assess the accuracy and best practices of computational fluid dynamics solvers. The computational fluid dynamics flow solver ANSYS-FLUENT is employed in the investigation of compressible turbulent flow through the S duct. A second-order accurate, steady, density-based solver is employed in a finite-volume framework. The three-dimensional Reynolds-averaged Navier–Stokes equations are solved on a structured mesh with a number of turbulence models, namely, the Spalart–Allmaras, $k\text{-}\epsilon$, $k\text{-}\omega$ shear stress transport, and transition shear stress transport models, and the results are compared with the available experimental data. The computed results capture the flowfield and pressure recovery with acceptable accuracy when compared to the experimental data. The turbulence model giving the best results is identified.