Impacts of passive flow control techniques on Reynolds analogy breakdown
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Date
2025
Authors
Rezaei, R.A.
Jafari, A.
Hoang, V.T.
Arjomandi, M.
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International Communications in Heat and Mass Transfer, 2025; 165(Part B):108959-1-108959-24
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Razieh A. Rezaei, Azadeh Jafari, Van Thuan Hoang, Maziar Arjomandi
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Abstract
A favourable breakdown of the Reynolds analogy is characterised by enhanced heat transfer while minimising drag. This study investigates the flow features generated by applying passive flow control techniques, such as surface roughness, fins and riblets, where a favourable breakdown of the Reynolds analogy is required. Flow features can favourably break the Reynolds analogy if they produce greater turbulent or dispersive heat flux than the corresponding momentum flux. Currently, no reports indicate that homogeneous surface roughness can favourably break down the Reynolds analogy. This is primarily due to the dominance of pressure drag over viscous drag on rough surfaces. In contrast to rough surfaces, longitudinal riblets do not cause pressure drag and can result in a favourable breakdown of the Reynolds analogy for certain geometries. As we will discuss, the combination of the strong spanwise aligned Kelvin-Helmholtz (KH) rollers and weak streamwise aligned secondary flows is a promising approach for achieving a favourable breakdown of the Reynolds analogy in drag increasing riblets. However, more studies are needed to characterise KH rollers to generate KH rollers with desirable parameters. On the other hand, whether drag-reducing riblets can also achieve enhanced heat transfer remains unclear, as contradicting results have been reported.
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© 2025 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).