An advanced, high-effectiveness film-cooling design, the anti-vortex hole (AVH) has been investigated by several research groups and shown to mitigate or counter the vorticity generated by conventional holes and increase film effectiveness at high blowing ratios and low freestream turbulence levels. [1, 2] The effects of increased turbulence on the AVH geometry were previously investigated and presented by researchers at West Virginia University (WVU), in collaboration with NASA, in a preliminary CFD study [3] on the film effectiveness and net heat flux reduction (NHFR) at high blowing ratio and elevated freestream turbulence levels for the adjacent AVH. The current paper presents the results of an extended numerical parametric study, which attempts to separate the effects of turbulence intensity and length-scale on film cooling effectiveness of the AVH. In the extended study, higher freestream turbulence intensity and larger scale cases were investigated with turbulence intensities of 5, 10 and 20% and length scales based on cooling hole diameter of Λx/dm = 1, 3 and 6. Increasing turbulence intensity was shown to increase the centerline, span-averaged and area-averaged adiabatic film cooling effectiveness. Larger turbulent length scales were shown to have little to no effect on the centerline, span-averaged and area-averaged adiabatic film-cooling effectiveness at lower turbulence levels, but slightly increased effect at the highest turbulence levels investigated.

A flat plate film cooling flow from a multi-exit hole configuration has been numerically simulated using both steady and unsteady Reynolds Averaged Navier Stokes (RANS and URANS) Computational Fluid Dynamics (CFD) formulations. This multi-exit hole concept, the Anti-Vortex Hole (AVH), has been developed and studied by previous research groups and shown to mitigate or counter the vorticity generated by conventional holes resulting in a more attached film cooling layer and higher film cooling effectiveness. The film cooling jets interaction with the free stream flow is a long studied area in gas turbine heat transfer. The present study numerically simulates the jet interaction with the multi-exit hole concept at a high blowing ratio (M = 2.0) and density ratio (DR = 2.0) in order to provide a more detailed, graphical explanation of the improvement in film cooling effectiveness. This paper presents a numerical study of the flow visualization of the interaction of film cooling jets with a subsonic crossflow. The contour plots of adiabatic cooling effectiveness were used to compare the multi-exit hole and conventional single hole configurations. The vortex structures in the flow were analyzed by URANS formulations and the effect of these vortices on the cooling effectiveness was investigated together with the coolant jet lift-off predictions. Quasi-Instantaneous Temperature Isosurface plots are used in the investigations of the effect of turbulence intensity on the cooling effectiveness and coolant jet coverage. The effect of varying turbulence intensity was investigated when analyzing the jets' interaction with the cross flow and the corresponding temperatures at the wall. The results show that as the turbulence intensity is increased, the cooling flow will stay more attached to the wall and have more pronounced lateral spreading far downstream of the cooling holes.

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An advanced, high-effectiveness film cooling design, the antivortex hole (AVH) has been investigated by several research groups and shown to mitigate or counter the vorticity generated by conventional holes and increase film effectiveness at high blowing ratios and low freestream turbulence levels. The effects of increased turbulence on an AVH geometry were previously investigated in a preliminary steady computational fluid dynamics (CFD) study by Hunley et al. on the film effectiveness and net heat flux reduction (NHFR) at high blowing ratio. The current paper presents the results of an extended numerical parametric study, which attempts to separate the effects of turbulence intensity and length scale on film cooling performance of the AVH concept at high blowing ratio (2.0) and density ratio (2.0). In this extended study, steady Reynolds-averaged Navier–Stokes (RANS) analysis was performed with turbulence intensities of 5, 10, and 20% and length scales based on cooling hole diameter of Λx/dm = 1, 3, and 6. Increasing turbulence intensity was shown to increase the centerline, span-averaged, and area-averaged adiabatic film cooling effectiveness and NHFR. Larger turbulent length scales in the steady RANS analysis were shown to have little to no effect on the centerline, span-averaged, and area-averaged adiabatic film cooling effectiveness and NHFR at lower turbulence levels, but moderate effect at the highest turbulence levels investigated. Heat transfer results were in good agreement with the findings from adiabatic cases from previous work. Unsteady RANS results also provided supplementary flow visualization for the AVH film cooling flow under varying turbulence levels.

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