On the friction drag reduction mechanism of streamwise wall fluctuations
Understanding how to decrease the friction drag exerted by a fluid on a solid surface is becoming increasingly important to address key societal challenges, such as decreasing the carbon footprint of transport. Well-established techniques are not yet available for friction drag reduction. Direct num...
| Main Authors: | , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
Elsevier
2020
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| _version_ | 1797101154690138112 |
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| author | Jozsa, T Balaras, E Kashtalyan, M Borthwick, AGL Viola, IM |
| author_facet | Jozsa, T Balaras, E Kashtalyan, M Borthwick, AGL Viola, IM |
| author_sort | Jozsa, T |
| collection | OXFORD |
| description | Understanding how to decrease the friction drag exerted by a fluid on a solid surface is becoming increasingly important to address key societal challenges, such as decreasing the carbon footprint of transport. Well-established techniques are not yet available for friction drag reduction. Direct numerical simulation results obtained by Józsa et al. (2019) previously indicated that a passive compliant wall can decrease friction drag by sustaining the drag reduction mechanism of an active control strategy. The proposed compliant wall is driven by wall shear stress fluctuations and responds with streamwise wall velocity fluctuations. The present study aims to clarify the underlying physical mechanism enabling the drag reduction of these active and passive control techniques. Analysis of turbulence statistics and flow fields reveals that both compliant wall and active control amplify streamwise velocity streaks in the viscous sublayer. By doing so, these control methods counteract dominant spanwise vorticity fluctuations in the near-wall region. The lowered vorticity fluctuations lead to an overall weakening of vortical structures which then mitigates momentum transfer and results in lower friction drag. These results might underpin the further development and practical implementation of these control strategies.
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| first_indexed | 2024-03-07T05:47:48Z |
| format | Journal article |
| id | oxford-uuid:e7cc36a9-7c52-4a8f-8aab-4c6b1e15ff8b |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T05:47:48Z |
| publishDate | 2020 |
| publisher | Elsevier |
| record_format | dspace |
| spelling | oxford-uuid:e7cc36a9-7c52-4a8f-8aab-4c6b1e15ff8b2022-03-27T10:41:49ZOn the friction drag reduction mechanism of streamwise wall fluctuationsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:e7cc36a9-7c52-4a8f-8aab-4c6b1e15ff8bEnglishSymplectic ElementsElsevier2020Jozsa, TBalaras, EKashtalyan, MBorthwick, AGLViola, IMUnderstanding how to decrease the friction drag exerted by a fluid on a solid surface is becoming increasingly important to address key societal challenges, such as decreasing the carbon footprint of transport. Well-established techniques are not yet available for friction drag reduction. Direct numerical simulation results obtained by Józsa et al. (2019) previously indicated that a passive compliant wall can decrease friction drag by sustaining the drag reduction mechanism of an active control strategy. The proposed compliant wall is driven by wall shear stress fluctuations and responds with streamwise wall velocity fluctuations. The present study aims to clarify the underlying physical mechanism enabling the drag reduction of these active and passive control techniques. Analysis of turbulence statistics and flow fields reveals that both compliant wall and active control amplify streamwise velocity streaks in the viscous sublayer. By doing so, these control methods counteract dominant spanwise vorticity fluctuations in the near-wall region. The lowered vorticity fluctuations lead to an overall weakening of vortical structures which then mitigates momentum transfer and results in lower friction drag. These results might underpin the further development and practical implementation of these control strategies. |
| spellingShingle | Jozsa, T Balaras, E Kashtalyan, M Borthwick, AGL Viola, IM On the friction drag reduction mechanism of streamwise wall fluctuations |
| title | On the friction drag reduction mechanism of streamwise wall fluctuations |
| title_full | On the friction drag reduction mechanism of streamwise wall fluctuations |
| title_fullStr | On the friction drag reduction mechanism of streamwise wall fluctuations |
| title_full_unstemmed | On the friction drag reduction mechanism of streamwise wall fluctuations |
| title_short | On the friction drag reduction mechanism of streamwise wall fluctuations |
| title_sort | on the friction drag reduction mechanism of streamwise wall fluctuations |
| work_keys_str_mv | AT jozsat onthefrictiondragreductionmechanismofstreamwisewallfluctuations AT balarase onthefrictiondragreductionmechanismofstreamwisewallfluctuations AT kashtalyanm onthefrictiondragreductionmechanismofstreamwisewallfluctuations AT borthwickagl onthefrictiondragreductionmechanismofstreamwisewallfluctuations AT violaim onthefrictiondragreductionmechanismofstreamwisewallfluctuations |