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Large eddy simulation of smooth–rough–smooth transitions in turbulent channel flows

Saito, Namiko and Pullin, D. I. (2014) Large eddy simulation of smooth–rough–smooth transitions in turbulent channel flows. International Journal of Heat and Mass Transfer, 78 . pp. 707-720. ISSN 0017-9310. http://resolver.caltech.edu/CaltechAUTHORS:20141024-110858324

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Abstract

We describe a high Reynolds number large-eddy-simulation (LES) study of turbulent flow in a long channel of length 128 channel half heights, δ, with the walls consisting of roughness strips where the long stream-wise extent invites a full relaxation of the mean velocities within each strip. The channel is stream-wise periodic and strips are oriented transverse to the flow resulting in repeated transitions between smooth and rough surfaces along the stream-wise direction. The present LES uses a wall model that contains Colebrook’s empirical formula as a roughness correction to both the local and dynamic calculation of the friction velocity and also the LES wall boundary condition. This operates point-wise across wall surfaces, and hence changes in the outer flow can be viewed as a response to the temporally and/or spatially variant roughness distribution. At the wall surface, dynamically calculated levels of time- and span-wise-averaged friction velocity u_τ[bar](x) over/undershoot and then fully recover towards their smooth or rough state over a stream-wise distance of order 10–30 δδ depending on both roughness and Reynolds number. Also, the initial response rate in u_τ[bar] shows Reynolds number and roughness dependence over both transitions. The growth rate of the internal boundary layer (IBL), defined by the abrupt change in stream-wise turbulent intensity, is found to grow as x^0.70 on average over multiple simulation conditions for the case of a smooth-to-rough transition, which agrees with the experimental results of Antonia and Luxton (1971) [1] and Efros and Krogstad (2011) [2]. IBL profiles demonstrate a good collapse on δ/log(Re^(*)_(τ)), where View the Re^(*)_(τ) is the local Reynolds number based on u_τ[bar] at the point of full recovery.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.ijheatmasstransfer.2014.06.088DOIArticle
http://www.sciencedirect.com/science/article/pii/S0017931014005614PublisherArticle
Additional Information:© 2014 Elsevier Ltd. Received 12 December 2013; Received in revised form 28 June 2014; Accepted 29 June 2014; Available online 6 August 2014. This work has been supported in part by the National Science Foundation under Grant CBET-1235605. Helpful discussions with Beverley McKeon are gratefully acknowledged.
Group:GALCIT
Funders:
Funding AgencyGrant Number
NSFCBET-1235605
Subject Keywords:Turbulent; High Reynolds number; LES; Roughness; Wall model
Record Number:CaltechAUTHORS:20141024-110858324
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20141024-110858324
Official Citation:Saito, N., & Pullin, D. I. (2014). Large eddy simulation of smooth–rough–smooth transitions in turbulent channel flows. International Journal of Heat and Mass Transfer, 78(0), 707-720. doi: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2014.06.088
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50784
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:27 Oct 2014 18:57
Last Modified:21 Sep 2016 22:36

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