Scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall

Scaling analysis of the velocity profiles in strongly drag reduced flows reveals that the slope of the logarithmic part depends on the amount of drag reduction (DR). Unlike DR due to polymeric fluids, the slope changes gradually and can be predicted by the analysis. Furthermore, the intercept of the...

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Main Author: Skote, Martin
Other Authors: School of Mechanical and Aerospace Engineering
Format: Article
Language:English
Published: 2016
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Online Access:https://hdl.handle.net/10356/81836
http://hdl.handle.net/10220/41041
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-818362023-03-04T17:13:23Z Scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall Skote, Martin School of Mechanical and Aerospace Engineering Turbulent boundary layer Oscillating wall Scaling analysis of the velocity profiles in strongly drag reduced flows reveals that the slope of the logarithmic part depends on the amount of drag reduction (DR). Unlike DR due to polymeric fluids, the slope changes gradually and can be predicted by the analysis. Furthermore, the intercept of the profiles is found to vary linearly with the DR. Two velocity scales are utilized: the reference (undisturbed) and the actual friction velocity. The theory is based on the assumption that the near-wall linear region is only governed by the actual friction velocity, while the outer part is governed by the reference friction velocity. As a result, logarithmic part is influenced by both velocity scales and the slope of the velocity profile is directly linked to the DR. The theoretically obtained results are verified by data from six previously performed direct numerical simulations (DNSs) of boundary layers over spatial and temporal wall oscillations, with a wide range of resulting DR. The theory is further supported by data from numerous investigations (DNSs as well as experiments) of wall-bounded flows forced by various forms of oscillating wall-motion. The assumption that the outer part is unaffected by the actual friction velocity limits the validity of the proposed log-law to flows not fully adapted to the imposed wall forcing, hence the theory provides a measure of the level of adjustment. In addition, a fundamental difference in the applicability of the theory to spatially developing boundary flow and infinite channel flow is discussed. MOE (Min. of Education, S’pore) Accepted version 2016-08-02T06:38:34Z 2019-12-06T14:41:13Z 2016-08-02T06:38:34Z 2019-12-06T14:41:13Z 2014 2014 Journal Article Skote, M. (2014). Scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall. International Journal of Heat and Fluid Flow, 50, 352–358. 0142-727X https://hdl.handle.net/10356/81836 http://hdl.handle.net/10220/41041 10.1016/j.ijheatfluidflow.2014.09.006 185579 en International Journal of Heat and Fluid Flow © 2014 Elsevier. This is the author created version of a work that has been peer reviewed and accepted for publication by International Journal of Heat and Fluid Flow, Elsevier. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [http://dx.doi.org/10.1016/j.ijheatfluidflow.2014.09.006]. 17 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Turbulent boundary layer
Oscillating wall
spellingShingle Turbulent boundary layer
Oscillating wall
Skote, Martin
Scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall
description Scaling analysis of the velocity profiles in strongly drag reduced flows reveals that the slope of the logarithmic part depends on the amount of drag reduction (DR). Unlike DR due to polymeric fluids, the slope changes gradually and can be predicted by the analysis. Furthermore, the intercept of the profiles is found to vary linearly with the DR. Two velocity scales are utilized: the reference (undisturbed) and the actual friction velocity. The theory is based on the assumption that the near-wall linear region is only governed by the actual friction velocity, while the outer part is governed by the reference friction velocity. As a result, logarithmic part is influenced by both velocity scales and the slope of the velocity profile is directly linked to the DR. The theoretically obtained results are verified by data from six previously performed direct numerical simulations (DNSs) of boundary layers over spatial and temporal wall oscillations, with a wide range of resulting DR. The theory is further supported by data from numerous investigations (DNSs as well as experiments) of wall-bounded flows forced by various forms of oscillating wall-motion. The assumption that the outer part is unaffected by the actual friction velocity limits the validity of the proposed log-law to flows not fully adapted to the imposed wall forcing, hence the theory provides a measure of the level of adjustment. In addition, a fundamental difference in the applicability of the theory to spatially developing boundary flow and infinite channel flow is discussed.
author2 School of Mechanical and Aerospace Engineering
author_facet School of Mechanical and Aerospace Engineering
Skote, Martin
format Article
author Skote, Martin
author_sort Skote, Martin
title Scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall
title_short Scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall
title_full Scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall
title_fullStr Scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall
title_full_unstemmed Scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall
title_sort scaling of the velocity profile in strongly drag reduced turbulent flows over an oscillating wall
publishDate 2016
url https://hdl.handle.net/10356/81836
http://hdl.handle.net/10220/41041
_version_ 1759857869540294656