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Research Papers

# Effects of Reynolds Number and Freestream Turbulence Intensity on the Unsteady Boundary Layer Development on an Ultra-High-Lift Low Pressure Turbine Airfoil

[+] Author and Article Information
Xue Feng Zhang

Gas Turbine Laboratory, Institute for Aerospace Research, National Research Council Canada, M-10, 1200 Montreal Road, Ottawa, ON, K1A 0R6, Canada

Howard Hodson

J. Turbomach 132(1), 011016 (Sep 18, 2009) (10 pages) doi:10.1115/1.3106031 History: Received November 18, 2008; Revised December 18, 2008; Published September 18, 2009

## Abstract

The effects of Reynolds numbers and the freestream turbulence intensities (FSTIs) on the unsteady boundary layer development on an ultra-high-lift low-pressure turbine airfoil, so-called T106C, are investigated. The measurements were carried out at both $Tu=0.5%$ and 4.0% within a range of Reynolds numbers, based on the blade chord and the isentropic exit velocity, between 100,000 and 260,000. The interaction between the unsteady wake and the boundary layer depends on both the strength of the wake and the status of the boundary layer. At $Tu=0.5%$, both the wake’s high turbulence and the negative jet behavior of the wake dominate the interaction between the unsteady wake and the separated boundary layer on the suction surface of the airfoil. Since the wake turbulence cannot induce transition before separation on this ultra-high-lift blade, the negative jet of the wake has the opportunity to induce a rollup vortex. At $Tu=4.0%$, the time-mean separation on the suction surface is much smaller. With elevated FSTI, the turbulence in the wake just above the boundary layer is no longer distinguishable from the background turbulence level. The unsteady boundary layer transition is dominated by the wake’s negative jet induced boundary layer variation.

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## Figures

Figure 1

Schematic of T106C moving-bar test rig with PIV measurement system

Figure 2

Total pressure loss coefficients

Figure 3

Time-mean surface pressure coefficient distributions and unsteady pressure variations at Tu=0.5%

Figure 4

Normalized unsteady surface static pressures on the suction surface

Figure 5

Unsteady normalized velocity at selected instants on the suction surface at Re2is=130,000 and Tu=0.5%

Figure 6

Unsteady normalized velocity at selected instants on the suction surface at Re2is=130,000 and Tu=0.5% from PIV measurements

Figure 7

Unsteady normalized rms of velocity at selected streamwise locations on the suction surface at Re2is=130,000 and Tu=0.5%

Figure 8

Ensemble-averaged turbulent kinetic energy (TKE) and velocity perturbation vectors in the blade passage of T106 (18)

Figure 9

s-t diagram of ensemble-averaged unsteady boundary layer (BL) momentum thickness θ on the suction surface at Re2is=130,000 and Tu=0.5%

Figure 10

Normalized rms of velocity at selected streamwise locations on the suction surface at Re2is=210,000 and Tu=0.5%

Figure 11

s-t diagram of ensemble-averaged unsteady B.L. momentum thickness θ on the suction surface at Re2is=210,000 and Tu=0.5%

Figure 12

Time-mean surface pressure coefficient distributions and unsteady pressure scatters at Re2is=130,000

Figure 13

Unsteady normalized rms of velocity at selected streamwise locations on the suction surface at Re2is=130,000 and Tu=4.0%

Figure 14

s-t diagram of ensemble-averaged unsteady B.L. momentum thickness θ on the suction surface at Re2is=130,000 and Tu=4.0%

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