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

Abstract

Large eddy simulations were performed to study the effect of a microramp on an inclined turbulent jet interacting with a crossflow in a filmcooling configuration. The microramp vortex generator is placed downstream of the filmcooling jet. Changes in vortex structure and filmcooling effectiveness are evaluated. Coherent turbulent structures characteristic of a jet in a crossflow are analyzed and the genesis of the counterrotating vortex pair in the jet is discussed. Results are reported for two filmcooling 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 microramp improves filmcooling effectiveness by generating nearwall counterrotating vortices which help entrain coolant from the jet and transport it to the surface. The pair of vortices generated by the microramp are of opposite sense to the vortex pair embedded in the jet.