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Turbulent heat transfer in channels with irregular roughness

Turbulent heat transfer in channels with irregular roughness
Turbulent heat transfer in channels with irregular roughness
It is well known that rough surfaces affect turbulent flows significantly. How such surfaces affect turbulent heat transfer is less well understood. To gain more insight, we have performed a series of direct numerical simulations of turbulent heat transfer in a channel flow with grit-blasted surfaces. An immersed boundary method is used to account for the rough surface. A source term in the thermal energy balance is used to maximise the analogy between the transport of heat and the transport of streamwise momentum. The wall roughness size is varied from to =120. Turbulence statistics like mean temperature profile, mean temperature fluctuations and heat fluxes are presented. The structure of the turbulent temperature field is analysed in detail. Recirculation zones, which are the result of an adverse pressure gradient, have a profound effect on heat transfer. This is important as it leads to the wall-scaled mean temperature profiles being of larger magnitude than the mean velocity profiles both inside and outside the roughness layer. This means that the temperature wall roughness function is different from the momentum wall roughness function . Since the bulk temperature and velocity depend on and , it was shown that the Stanton number and the skin friction factor directly depend on and , respectively. Therefore, the failure of the Reynolds analogy in fully rough conditions can be directly related to the difference between and .
0017-9310
454-467
Peeters, J.W.R.
be0aa7d2-9a70-4745-b0da-8dad7cc91403
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97
Peeters, J.W.R.
be0aa7d2-9a70-4745-b0da-8dad7cc91403
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97

Peeters, J.W.R. and Sandham, N.D. (2019) Turbulent heat transfer in channels with irregular roughness. International Journal of Heat and Mass Transfer, 138, 454-467. (doi:10.1016/j.ijheatmasstransfer.2019.04.013).

Record type: Article

Abstract

It is well known that rough surfaces affect turbulent flows significantly. How such surfaces affect turbulent heat transfer is less well understood. To gain more insight, we have performed a series of direct numerical simulations of turbulent heat transfer in a channel flow with grit-blasted surfaces. An immersed boundary method is used to account for the rough surface. A source term in the thermal energy balance is used to maximise the analogy between the transport of heat and the transport of streamwise momentum. The wall roughness size is varied from to =120. Turbulence statistics like mean temperature profile, mean temperature fluctuations and heat fluxes are presented. The structure of the turbulent temperature field is analysed in detail. Recirculation zones, which are the result of an adverse pressure gradient, have a profound effect on heat transfer. This is important as it leads to the wall-scaled mean temperature profiles being of larger magnitude than the mean velocity profiles both inside and outside the roughness layer. This means that the temperature wall roughness function is different from the momentum wall roughness function . Since the bulk temperature and velocity depend on and , it was shown that the Stanton number and the skin friction factor directly depend on and , respectively. Therefore, the failure of the Reynolds analogy in fully rough conditions can be directly related to the difference between and .

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More information

Accepted/In Press date: 3 April 2019
e-pub ahead of print date: 20 April 2019
Published date: August 2019

Identifiers

Local EPrints ID: 430639
URI: https://eprints.soton.ac.uk/id/eprint/430639
ISSN: 0017-9310
PURE UUID: bccc02cd-e3ba-4453-8758-ec1699299e6b
ORCID for N.D. Sandham: ORCID iD orcid.org/0000-0002-5107-0944

Catalogue record

Date deposited: 07 May 2019 16:30
Last modified: 02 Aug 2019 00:35

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