This paper reports results from the use of laser Doppler anemometry (LDA) to measure the mean and the fluctuating flow field in a U-bend of strong curvature, Rc/D = 0.65, that is either stationary or rotating in orthogonal mode (the axis of rotation being parallel to the axis of curvature). The data acquisition system enables a stationary optical fibre probe to collect flow data from a rotating U-bend sweeping past it. Three cases have been examined all concerning a flow Reynolds number of 100,000; a stationary case, a case of positive rotation (the pressure side of the duct coincides with the outer side of the U-bend) at a Rotational number (ΩD/Um) of 0.2 and a case of negative rotation at a Rotational number of −0.2. Measurements have been obtained along the symmetry plane of the duct and also along a plane near top wall. The most important influence on the development of the mean and the turbulence flow fields is exerted by the streamwise pressure gradients that occur over the entry and exit regions of the U-bend. In the stationary case a 3-dimensional separation bubble is formed along the inner wall at the 90° location and it extends to about 2 diameters downstream of the bend causing the generation of high turbulence levels. Along the outer side, opposite the separation bubble, turbulence levels are suppressed due to streamwise flow acceleration. For the Rotation numbers examined, the Coriolis force also has a significant effect on the flow development. Positive rotation doubles the length of the separation bubble and generally suppresses turbulence levels. Negative rotation causes an extra separation bubble at the bend entry, raises turbulence levels within and downstream of the bend, increases velocity fluctuations in the cross-duct direction within the bend and generates strong secondary motion after the bend exit. It is hoped that the detailed information produced in this study will assist in the development of turbulence models suitable for the numerical computation of flow and heat transfer inside blade-cooling passages.
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ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition
June 13–16, 1994
The Hague, Netherlands
Conference Sponsors:
- International Gas Turbine Institute
ISBN:
978-0-7918-7887-3
PROCEEDINGS PAPER
LDA Investigation of the Flow Development Through Rotating U-DUCTS
B. E. Launder
B. E. Launder
UMIST, Manchester, UK
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S. C. Cheah
UMIST, Manchester, UK
H. Iacovides
UMIST, Manchester, UK
D. C. Jackson
UMIST, Manchester, UK
H. Ji
UMIST, Manchester, UK
B. E. Launder
UMIST, Manchester, UK
Paper No:
94-GT-226, V005T16A003; 9 pages
Published Online:
February 18, 2015
Citation
Cheah, SC, Iacovides, H, Jackson, DC, Ji, H, & Launder, BE. "LDA Investigation of the Flow Development Through Rotating U-DUCTS." Proceedings of the ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; General. The Hague, Netherlands. June 13–16, 1994. V005T16A003. ASME. https://doi.org/10.1115/94-GT-226
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