Film-Cooling From Holes With Expanded Exits: A Comparison of Computational Results With Experiments

Abstract

A 3D Navier-Stokes code, together with the standard k-ϵ model with wall function approach, was used to investigate the flowfield in the vicinity of three different single scaled-up film-cooling holes. The hole geometries include a cylindrical hole, a hole with laterally expanded exit, and a hole with forward-laterally expanded exit. Comparisons of numerical results with detailed flowfield measurements of mean velocity and turbulent quantities are presented for a blowing ratio and density ratio of unity. Additionally, experimental data for different blowing ratios and a density ratio of about two are taken to perform validation of the code for adiabatic film-cooling effectiveness prediction. Results show that for both the round and the expanded hole geometries the code is able to capture all dominating flow structures of this jet in crossflow problem. However, discrepancies are found when comparing the flowfield inside the hole and at the hole exit. In particular, jet location at the hole exit differs significantly from measurement for the expanded hole geometries. For the adiabatic film-cooling effectiveness, it is shown that for round and expanded hole exits the intensity of the shear regions and the source of turbulence, respectively, have a strong influence on the predictive capability of the numerical code.