Turbulence Measurements of Separate-Flow Nozzles with Pylon Interaction Using Particle Image Velocimetry

Particle image velocimetry measurements for separate-flow nozzles with bypass ratio five have recently been obtained in the NASA Langley Jet Noise Laboratory. The six configurations tested include a baseline configuration with round core and fan nozzles, an eight-chevron core nozzle at two different clocking positions, and repeats of these configurations with a pylon included. One run condition representative of takeoff was investigated for all cases. The unsteady flowfield measurements complement recent computational, acoustic, and mean flowfield studies performed at NASA Langley for the same nozzle configurations and run condition. The baseline configuration measurements show good agreement with existing mean and turbulent flowfield data. Nonetheless, the baseline configuration turbulence profile indicates an asymmetric flowfield, despite careful attention to concentricity. The presence of the pylon increases the upper shear layer turbulence levels while simultaneously decreasing the turbulence levels in the lower shear layer. In addition, a slightly shorter potential core length is observed with the addition of the pylon. Finally, comparisons of computational results with current measurements are favorable for mean flow, slightly overpredicted for Reynolds shear stress, and underpredicted for Reynolds normal stress components. [PUBLICATION ABSTRACT]