Transition Modeling for Vortex Generating Jets on Low Pressure Turbine Profiles

Abstract

Steady blowing vortex generating jets (VGJ) on highlyloaded lowpressure turbine profiles have shown to be a promising way to decrease total pressure losses at low Reynoldsnumbers by reducing laminar separation. In the present paper, the state of the art turbomachinery design code TRACE with RANS turbulence closure and coupled خ³Reخک transition model is applied to the prediction of typical aerodynamic design parameters of various VGJ configurations in steady simulations. Highspeed cascade wind tunnel experiments for a wide range of Reynoldsnumbers, two VGJ positions, and three jet blowing ratios are used for validation. Since the original transition model overpredicts separation and losses at Re2is≤100آ·103, an extra mode for VGJ induced transition is introduced. Whereas the criterion for transition is modeled by a filtered Q vortex criterion the transition development itself is modeled by a reduction of the local transitiononset momentumthickness Reynolds number. The new model significantly improves the quality of the computational results by capturing the corresponding local transition process in a physically reasonable way. This is shown to yield an improved quantitative prediction of surface pressure distributions and total pressure losses.