This project, done at the Illinois Institute of Technology, investigates turbulent boundary-layer separation in axisymmetric diffusers using computational fluid dynamics (CFD). Simulations were performed in ANSYS Fluent to replicate and validate experimental results from NACA Report 1201, with a focus on how turbulence modeling and inlet conditions influence separation behavior and pressure recovery.

A Reynolds number sweep was conducted across multiple diffuser geometries, including 12°, 18°, and 23° expansion angles, covering flow regimes from fully attached to strongly separated. Three turbulence models including Spalart–Allmaras, k–ε, and k–ω SST were evaluated to assess their ability to predict separation onset, wall shear behavior, and performance losses.

Results were analyzed through wall shear stress distributions, pressure recovery trends, and boundary-layer profiles, providing insight into model sensitivity and the physical mechanisms driving diffuser performance degradation under adverse pressure gradients.