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A comparison of spreading angles of turbulent wedges in velocity and thermal boundary layers

A comparison of spreading angles of turbulent wedges in velocity and thermal boundary layers
A comparison of spreading angles of turbulent wedges in velocity and thermal boundary layers
Turbulent wedges induced by a three-dimensional surface roughness placed in a laminar boundary layer over a flat plate were visualized for the first time using both shear-sensitive and temperature-sensitive liquid crystals. The experiments were carried out at zero pressure gradient and two different levels of favorable pressure gradients. The purpose of this investigation was to examine the spreading angles of turbulent wedges indicated by their associated surface shear stresses and heat transfer characteristics and hence obtain further insight about the difference in the behavior of transitional momentum and thermal boundary layers when a streamwise pressure gradient exists. It was found that under a zero pressure gradient the spreading angles indicated by the two types of liquid crystals are the same, but the difference increases as the level of favorable pressure gradient increases with the angle indicated by temperature-sensitive liquid crystals being smaller. The results from the present study suggest that the spanwise growth of a turbulent region is smaller in a thermal boundary layer than in its momentum counterpart and this seems to be responsible for the inconsistency in transition zone length indicated by the distribution of heat transfer rate and boundary layer shape factor reported in the literature. This finding would have an important implication to the transition modeling of thermal boundary layers over gas turbine blades.
0098-2202
267-274
Zhong, S.
e52648be-29fe-4597-bece-e28eec163b8b
Chong, T.P.
df7a2c0c-9f56-44dd-b668-8ef83d3e2c0d
Hodson, H.P.
33764088-9890-4258-8b49-70ebcd71d488
Zhong, S.
e52648be-29fe-4597-bece-e28eec163b8b
Chong, T.P.
df7a2c0c-9f56-44dd-b668-8ef83d3e2c0d
Hodson, H.P.
33764088-9890-4258-8b49-70ebcd71d488

Zhong, S., Chong, T.P. and Hodson, H.P. (2003) A comparison of spreading angles of turbulent wedges in velocity and thermal boundary layers. Journal of Fluids Engineering, 125 (2), 267-274. (doi:10.1115/1.1539871).

Record type: Article

Abstract

Turbulent wedges induced by a three-dimensional surface roughness placed in a laminar boundary layer over a flat plate were visualized for the first time using both shear-sensitive and temperature-sensitive liquid crystals. The experiments were carried out at zero pressure gradient and two different levels of favorable pressure gradients. The purpose of this investigation was to examine the spreading angles of turbulent wedges indicated by their associated surface shear stresses and heat transfer characteristics and hence obtain further insight about the difference in the behavior of transitional momentum and thermal boundary layers when a streamwise pressure gradient exists. It was found that under a zero pressure gradient the spreading angles indicated by the two types of liquid crystals are the same, but the difference increases as the level of favorable pressure gradient increases with the angle indicated by temperature-sensitive liquid crystals being smaller. The results from the present study suggest that the spanwise growth of a turbulent region is smaller in a thermal boundary layer than in its momentum counterpart and this seems to be responsible for the inconsistency in transition zone length indicated by the distribution of heat transfer rate and boundary layer shape factor reported in the literature. This finding would have an important implication to the transition modeling of thermal boundary layers over gas turbine blades.

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Published date: March 2003

Identifiers

Local EPrints ID: 10318
URI: http://eprints.soton.ac.uk/id/eprint/10318
ISSN: 0098-2202
PURE UUID: 4405c056-27a4-4b2e-81cd-a329128f6230

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Date deposited: 19 Jan 2005
Last modified: 15 Mar 2024 04:59

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Contributors

Author: S. Zhong
Author: T.P. Chong
Author: H.P. Hodson

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