Large Eddy Simulations of Film-Cooling Flows With a Micro-Ramp Vortex Generator

Large eddy simulations were performed to study the effect of a micro-ramp on an inclined turbulent jet interacting with a cross-flow in a film-cooling configuration. The micro-ramp vortex generator is placed downstream of the film-cooling jet. Changes in vortex structure and film-cooling effectiveness are evaluated. Coherent turbulent structures characteristic of a jet in a cross-flow are analyzed and the genesis of the counter-rotating vortex pair in the jet is discussed. Results are reported for two film-cooling configurations, where the primary difference is the way the jet inflow boundary conditions are prescribed. In the first configuration, the jet conditions are prescribed using a precursor simulation and in the second the jet is modeled using a plenum/pipe configuration. The latter configuration was designed based on previous wind tunnel experiments at NASA Glenn Research Center, and the present results are meant to supplement those experiments. It is found that the micro-ramp improves film-cooling effectiveness by generating near-wall counter-rotating vortices which help entrain coolant from the jet and transport it to the surface. The pair of vortices generated by the micro-ramp are of opposite sense to the vortex pair embedded in the jet.