Large-eddy simulation of an inclined round jet issuing into a crossflow

For understanding of film cooling flow fields on gas turbine blades, this paper reports on a series of large-eddy simulations of an inclined round jet issuing into a crossflow. Simulations were performed at four blowing ratios, BR = 0.1, 0.5, 0.7 and 1.0, and the Reynolds number, Re = 15,300, based on the crossflow velocity and film cooling hole diameter. Results showed that the cooling jet flow structure drastically changed with the blowing ratio. A pair of rear vortices and hairpin vortices were observed for BR = 0.1. A horseshoe vortex periodically ejected, a pair of hanging vortices, a pair of rear vortices and hairpin vortices were observed for BR = 0.5. Similar vortical structures to BR = 0.5 were observed for BR = 0.7 although horseshoe vortex was not ejected periodically and stayed at a leading edge of the hole exit. For BR = 1.0, in addition to the former mentioned vortices, shear layer vortices and vertical streaks were observed on an upstream edge of the jet. It was consequently understood that the ubiquitous counter-rotating vortex pair which can be observed in the time-averaged flow field was actually originated in the different vortical structures with varying BR conditions. Temperature fields were also investigated to clarify how these different vortical structures affect the film cooling effectiveness.