CFD PREDICTIONS OF SINGLE ROW FILM COOLING WITH INCLINED HOLES: INFLUENCE OF HOLE OUTLET GEOMETRY

A CFD investigation of a single row of round inclined film cooling holes in a crossflow has been carried out with the view of investigating the discrepancies in the literature between predicted and measured results. The experimental results of Sinha et al. [1], Kohli et al. [40], Pedersen et al. [3] and others form the data base for validation of the CFD prediction of film cooling. Previous work in the literature is reviewed to show that CFD has had difficulty in obtaining agreement with these basic experimental film cooling results. However, most previous work has used tetrahedral meshes which gave poor agreement with experiments in the near hole region. In the present work it is shown by direct comparison of tetrahedral and hexahedral meshes, using the FLUENT code, with the same turbulence models, that only hexahedral meshes give good agreement with the experimental results in the near hole region. It is postulated that the reason is that the mesh structure is aligned with the flow and has more computational nodes in the important film cooling boundary layer. The hexahedral mesh was used with five turbulence models, which showed the standard k-epsilon model consistently gave the best agreement with experimental data for narrow angle film cooling. This CFD methodology was shown to be capable of predicting the influence on film cooling effectiveness of trench hole and larger diameter outlet hole geometries.