Provided are numerically predicted flow structural data for a flow passage with an impingement jet array, as well as numerically predicted surface Nusselt number data for the target surface of the passage, which are obtained using a SST $k-\omega$ turbulence closure model. The closure model and numerical prediction approach are validated by oil film flow visualization experimental results. Spatially averaged Nusselt number data are well represented by the impingement cooling temperature ratio correlation equation of Goodro et al., which indicates that associated Nusselt number ratios decrease as the T_w/T_o,in temperature ratio increases to values as high as 2.0. Local, spatially resolved Nusselt numbers and spanwise-averaged surface Nusselt number distributions for TR = 1.1 are consistently higher than TR = 2.0 values, when compared at particular surface locations. Cross flow influences are evidenced by spanwise-averaged, periodically varying Nusselt number values which generally increase with streamwise development. When surface oil flow visualization results are considered with numerically predicted turbulent viscosity ratio results, flow features include locally increased viscosity ratio values near impingement jet stagnation regions, horseshoe vortex signatures, and more focused and more narrow viscosity ratio distributions with streamwise development.

The effect of relative motion between the casing and turbine blade tip has been recognized as an important factor for tip aerothermal performance evaluation. Tight tip clearance is becoming one of the main objectives of engine manufacturers. This paper provides some insights on the topic that the impact of casing motion on the blade tip thermal performance could be different between nominal and tight tip clearances. A typical squealer tip geometry was employed, with coolant holes on the cavity floor near the pressure side rim. Three tip clearances, 1.1%, 0.6% and 0.2% of the span, are compared. The CFD method was validated against experimental data in the previous study. The results suggest that, in the tight tip situation, the effect of casing motion on cooling efficiency and flow structure is distinguished from the larger clearance situations. The scraping effect drives the leakage flow towards the blade suction surface, inducing high thermal load at tight clearance. The findings in this study highlight the importance of relative casing motion, especially at tight clearance.