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Low-frequency wake dynamics for a square-back vehicle with side trailing edge tapers.

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Title: Low-frequency wake dynamics for a square-back vehicle with side trailing edge tapers.
Authors: Pavia, Giancarlo1 G.Pavia@lboro.ac.uk, Passmore, Martin1, Varney, Max1
Source: Journal of Wind Engineering & Industrial Aerodynamics. Jan2019, Vol. 184, p417-435. 19p.
Subjects: Vector beams, Stable isotopes, Vortex methods, Aerofoils, Vortex motion
Abstract: Abstract In this paper, the effects of side trailing edge tapering on the wake of a simplified square-back vehicle are investigated. The tapered surfaces are reported to trigger a switch from a laterally asymmetric bi-stable wake to a vertically asymmetric stable wake. The wake structure reported in the literature for lateral symmetry breaking states is seen to rotate by 90 ∘ as the angle of the tapered surfaces ϕ s is increased. A 6 % drag reduction over the simple square-back case is reported for 6 ∘ < ϕ s < 12 ∘ . This gain is found to be the result of the stretching of the circular vortex responsible for the suction zone visible in any symmetry breaking state. A downwash dominated wake is observed in these conditions. The sensitivity of such a wake to small variations of the model pitch angle (for ϕ s = 12 ∘ ) is also assessed. As the pitch angle α is reduced from 0 ∘ to − 2 ∘ , the time averaged wake is reported to switch from a downwash dominated topology to an upwash dominated topology. A strengthening of the long-time instability is observed when the symmetry in the vertical direction is recovered and is accompanied with a 4.9 % reduction in base drag over the same model tested at α = 0 ∘ . Graphical abstract Image 1 Highlights • Side edge tapers can suppress the long-time instability while also reducing drag. • The long-time instability stems from the equilibrium between all shear layers. • Small perturbations of pitch angle can turn stable wakes into multi-stable wakes. • For a square-back bluff body, a lower drag wake is not always a more stable wake. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Wind Engineering & Industrial Aerodynamics is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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DbLabel: Engineering Source
An: 133786844
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  Data: Low-frequency wake dynamics for a square-back vehicle with side trailing edge tapers.
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  Data: Abstract In this paper, the effects of side trailing edge tapering on the wake of a simplified square-back vehicle are investigated. The tapered surfaces are reported to trigger a switch from a laterally asymmetric bi-stable wake to a vertically asymmetric stable wake. The wake structure reported in the literature for lateral symmetry breaking states is seen to rotate by 90 ∘ as the angle of the tapered surfaces ϕ s is increased. A 6 % drag reduction over the simple square-back case is reported for 6 ∘ &lt; ϕ s &lt; 12 ∘ . This gain is found to be the result of the stretching of the circular vortex responsible for the suction zone visible in any symmetry breaking state. A downwash dominated wake is observed in these conditions. The sensitivity of such a wake to small variations of the model pitch angle (for ϕ s = 12 ∘ ) is also assessed. As the pitch angle α is reduced from 0 ∘ to − 2 ∘ , the time averaged wake is reported to switch from a downwash dominated topology to an upwash dominated topology. A strengthening of the long-time instability is observed when the symmetry in the vertical direction is recovered and is accompanied with a 4.9 % reduction in base drag over the same model tested at α = 0 ∘ . Graphical abstract Image 1 Highlights • Side edge tapers can suppress the long-time instability while also reducing drag. • The long-time instability stems from the equilibrium between all shear layers. • Small perturbations of pitch angle can turn stable wakes into multi-stable wakes. • For a square-back bluff body, a lower drag wake is not always a more stable wake. [ABSTRACT FROM AUTHOR]
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  Data: &lt;i&gt;Copyright of Journal of Wind Engineering &amp; Industrial Aerodynamics is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder&#39;s express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.&lt;/i&gt; (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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    Identifiers:
      – Type: doi
        Value: 10.1016/j.jweia.2018.12.009
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 19
        StartPage: 417
    Subjects:
      – SubjectFull: Vector beams
        Type: general
      – SubjectFull: Stable isotopes
        Type: general
      – SubjectFull: Vortex methods
        Type: general
      – SubjectFull: Aerofoils
        Type: general
      – SubjectFull: Vortex motion
        Type: general
    Titles:
      – TitleFull: Low-frequency wake dynamics for a square-back vehicle with side trailing edge tapers.
        Type: main
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      – PersonEntity:
          Name:
            NameFull: Pavia, Giancarlo
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            NameFull: Passmore, Martin
      – PersonEntity:
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            NameFull: Varney, Max
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          Dates:
            – D: 01
              M: 01
              Text: Jan2019
              Type: published
              Y: 2019
          Identifiers:
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              Value: 01676105
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            – Type: volume
              Value: 184
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            – TitleFull: Journal of Wind Engineering & Industrial Aerodynamics
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