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Research Papers

Effects of Rotation and Buoyancy Forces on the Flow Field Behavior Inside a Triangular Rib Roughened Channel

[+] Author and Article Information
Luca Furlani

Polytechnical Department of Engineering
and Architecture,
University of Udine,
Udine 33100, Italy

Alessandro Armellini

Polytechnical Department of Engineering
and Architecture,
University of Udine, Udine 33100, Italy

Luca Casarsa

Polytechnical Department of Engineering
and Architecture,
University of Udine,
Udine 33100, Italy
e-mail: luca.casarsa@uniud.it

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 20, 2015; final manuscript received October 17, 2016; published online January 24, 2017. Assoc. Editor: Kenichiro Takeishi.

J. Turbomach 139(5), 051001 (Jan 24, 2017) (11 pages) Paper No: TURBO-15-1162; doi: 10.1115/1.4035103 History: Received July 20, 2015; Revised October 17, 2016

The flow field inside a triangular cooling channel for the leading edge of a gas turbine blade has been investigated. The efforts were focused on the investigation of the interaction between effects of rotation, of buoyancy forces, and those induced by turbulence promoters, i.e., perpendicular square ribs placed on both leading and trailing sides of the duct. Particle image velocimetry (PIV) and stereo-PIV measurements have been performed for ReDh = 104, rotation number of 0, 0.2, and 0.6, and buoyancy parameter equal to 0, 0.08, and 0.7. Coriolis secondary flows are detected in the duct cross section, but contrary to the smooth case, they are characterized by a single main vortex and are less affected by an increase of the rotation parameter. Moreover, their main topology is only marginally sensitive to the buoyancy forces. Conversely, the features of the recirculation structure downstream the ribs turned out to be more sensitive to both the buoyancy forces and to the stabilizing/destabilizing effect on the separated shear layer induced by rotation.

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References

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Figures

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Fig. 1

Illustration of forces and main flows features found in a rotating duct

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Fig. 2

Experimental facility, nomenclature, and positions of the PIV measurement planes: (a) left view, (b) front view-scale (2:1), (c) top view, (d) measurement plane position, and (e) rib-roughened wall: cross section detail

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Fig. 3

Measurement setup used for 2D-PIV on plane xy′ (a) and stereo-PIV on plane yz

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Fig. 4

Optical setup sketch and parallax error description

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Fig. 5

Parallax error compensation for 2D xy′ measurements: examples of calibration by means of dedicated target displacement (a) and (b) and resulting optical axis position (red dashed lines) and displacement correction fields (c) and (d)

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Fig. 6

Comparison of 2D and stereo-PIV data extracted on the intersection line of xy′ and yz planes of U and V′ profiles from 2D-PIV on xy′ and S-PIV on yz (a) leading side and (b) trailing side

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Fig. 7

Stream tracers and contour plot of the in-plane turbulence intensity in plane xy′ for Ro = 0

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Fig. 8

Stream tracers in plane xy′ for all the rotating cases

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Fig. 9

Contour plots of the turbulence intensity in plane xy′ for all the rotating cases

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Fig. 10

uv′〉 Reynolds stresses component extracted at y′/h = 0.5 from plane xy′, (a) static versus Ro = 0.2 and (b) static versus Ro = 0.6 test cases

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Fig. 11

Stream tracers (a) and (b) and contour plots of nondimensional streamwise velocity component U/Ub (c) and (d) in plane yz for the smooth channel configuration [5]

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Fig. 12

Stream tracers in plane yz for all the rotating cases

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Fig. 13

Contour plots of the nondimensional streamwise velocity component U/Ub in plane yz for all rotating cases

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Fig. 14

Tu levels in plane yz for Ro = 0.6

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