Research Papers

Investigation of Streamwise and Transverse Instabilities on Swept Cylinders and Implications for Turbine Blading

[+] Author and Article Information
J. P. Gostelow

e-mail: jpg7@le.ac.uk

A. Rona

e-mail: ar45@le.ac.uk

M. De Saint Jean

e-mail: myriam.desaintjean@gmail.com

S. J. Garrett

e-mail: sjg50@le.ac.uk

W. A. McMullan

e-mail: wam3@le.ac.uk
University of Leicester,
Leicester LE1 7RH, UK

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received June 29, 2012; final manuscript received August 30, 2012; published online June 28, 2013. Editor: David Wisler.

J. Turbomach 135(5), 051018 (Jun 28, 2013) (9 pages) Paper No: TURBO-12-1098; doi: 10.1115/1.4007833 History: Received June 29, 2012; Revised August 30, 2012

The starting point for this investigation was the observation of robust streamwise streaks in flow visualization on the suction surfaces of blades in a turbine cascade at subsonic and transonic speeds. The spanwise wavelength of an array of streamwise vortices had been predicted and is here confirmed experimentally. Observations of streaks on unswept turbine blades and on circular cylinders confirmed these earlier predictions, providing a firm basis for referencing the new measurements of vortical behavior. The observations made it clear that the boundary layers are highly three dimensional. In this paper observations of streamwise and transverse instabilities on swept circular cylinders, over a range of inclinations, are presented. The circular cylinder is a canonical case and observations relate the streamwise vorticity of the unswept case to the more aggressive crossflow instability at high sweep angles. Introducing sweep brings consideration of a wide range of instabilities. Prominent is crossflow instability resulting from the inflectional behavior of a three-dimensional boundary layer.

Copyright © 2013 by ASME
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Fig. 1

Suction surface flow visualization of turbine blade at a discharge Mach number of 1.16 [4]

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Fig. 2

Suction surface flow visualization of turbine blade by Halstead [5]

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Fig. 3

Circular cylinder mounted in wind tunnel

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Fig. 4

Measurements of spanwise wavelength on blading compared with Kestin and Wood predictions [8]

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Fig. 5

Surface flow visualization downstream of separation bubble on circular cylinder in NRC tunnel at a Mach number of 0.5

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Fig. 6

Measurements of spanwise wavelength on circular cylinders and comparison with Kestin and Wood predictions [8]

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Fig. 7

Lateral spacing between streaks, normalized by Kestin and Wood theory [8] (Eq. (1))

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Fig. 8

Normalized streak spacings, corrected for cosΛ term of Eq. (2)

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Fig. 9

Reynolds number effects on streak spacing of Poll [7] data and present data

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Fig. 10

Variation of streaks in present investigation from leading edge to laminar separation

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Fig. 11

Angle between streaks and normal to cylinder axis, for present results and those of Poll [7]




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