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3.5: The Friction Velocity or Shear Velocity u*

  • Page ID
    29287
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    The term friction velocity comes from the fact that \(\ \sqrt{( \boldsymbol{\tau}_{\mathrm{w}} / \boldsymbol{\rho}_{\mathrm{l}}}\) has the same unit as velocity and it has something to do with the wall friction force. The wall shear stress τw is often represented by friction velocity u*, defined by:

    \[\ \mathrm{u}_{*}=\sqrt{\frac{\tau_{\mathrm{w}}}{\rho_{\mathrm{l}}}}=\sqrt{\frac{\lambda_{1}}{8}} \cdot \mathrm{v}_{\mathrm{ls}}\]


    3.5: The Friction Velocity or Shear Velocity u* is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Sape A. Miedema via source content that was edited to conform to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.