Turbulence Model Enhancement Using Field Inversion for an Axisymmetric Blunt Body

Abstract

Separated flows are challenging to analyze numerically using Reynolds-averaged Navier-Stokes (RANS) simulation. A typical turbulence model for RANS is often unreliable for massively separated flow. Thus, this study aims to enhance a turbulence model for separated flows around blunt bodies. Numerical analysis of flows around axisymmetric blunt circular cylinders with various fineness ratios is conducted by solving the RANS equations with the Spalart-Allmaras (SA) turbulence model. The field inversion method is used to correct the SA model equation using sparse experimental data, and the proper correction is determined through an optimization process which minimizes errors associated with parameters of interest. In the current field inversion process, the SA model is modified using the aerodynamic drag measured in experiments. Although the optimization helps improve the SA model for the target drag, the overall flow field is not appropriately modified according to the test data. Therefore, the centerline velocity in the wake region is additionally included in the optimization process to modify the SA model. Consequently, the optimization involving both the aerodynamic drag and the wake centerline velocity significantly enhances the SA model, improving the prediction capability for the overall velocity field and the aerodynamic drag at the same time.