Abstract
In modern gas turbines, film cooling confronts complex near-wall flow conditions. Because of the low velocity ratio and the inclined injection in film cooling, the jet is more attached to the wall, making the influence of the local boundary layer critical. This paper investigates the interaction between the inclined jet and the mainstream boundary layer using large eddy simulation (LES). Four inflow boundary layer conditions were investigated, including a thin laminar case (δ/D = 0.5) and three turbulent cases with different thicknesses (δ/D = 0.5, 1.0, and 2.0). The jet velocity ratios are 0.23, 0.46, and 0.91 for each inflow condition. To consistently extract vortices of varying intensities, a local threshold was proposed using λci criterion. Based on the extracted vortices, a comprehensive analysis of the vortical strength, size, and position for horseshoe vortex (HSV), counter-rotating vortex pair (CRVP), and shear layer vortices (SLV) is performed under different inflow conditions. The results provide a clear picture of how HSV and CRVP form and evolve. Quantitative patterns are disclosed for the vortex lifting and vortical decay. Moreover, the thermal transport effects of HSV, CRVP, and SLV are examined. It was proven that these vortices dominate the coolant coverage, coolant core lifting, and thermal diffusion, respectively. Meanwhile, the jet has a significant impact on the near-wall flow development. The length of transition and the magnitude of thickening were discovered to be correlated with the jet velocity ratio and inflow thickness. Overall, these findings present a fresh perspective in understanding the flow and heat transport processes for inclined jet-in-crossflow.
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