Abstract
This paper deals with experimental and numerical investigations on the interaction between inlet freestream turbulence and boundary layers with separation bubble for low-pressure turbine airfoils under Ultra-High Lift condition. Reynolds number examined is 57,000, based on chord length and averaged exit velocity. Freestream turbulence intensity is from 0.80% (no gird condition) and 2.1% (with grid condition). Hot-wire probe measurements of the boundary layer on the suction surface for the airfoils are carried out to obtain time-averaged and time-resolved characteristics of the boundary layers under the influence of the freestream turbulence. Using turbulence grid installed upstream of the cascade. Numerical analysis based on high resolution Large Eddy Simulation is also executed to enhance the understanding on the flow field around turbine airfoils. Emphasis is placed on the relationship of inherent instability of the shear layer of the separation bubble and the freesteam turbulence. Results were indicative of characteristics of the boundary layer T-S wave and KH instability as no grid condition and captured bypass transition mode as grid condition.
