Normal and cross-flow Reynolds stresses: differences between confined and semi-confined flows |
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Authors: | Matthias H Buschmann Mohamed Gad-el-Hak |
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Institution: | 1. Institut für Luft- und K?ltetechnik Dresden, Bertolt-Brecht-Allee 20, 01309, Dresden, Germany 2. Department of Mechanical Engineering, Virginia Commonwealth University, Richmond, VA, 23284-3015, USA
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Abstract: | Understanding turbulent wall-bounded flows remains an elusive goal. Most turbulent phenomena are non-linear, complex and have
broad range of scales that are difficult to completely resolve. Progress is made only in minute steps and enlightening models
are rare. Herein, we undertake the effort to bundle several experimental and numerical databases to overcome some of these
difficulties and to learn more about the kinematics of turbulent wall-bounded flows. The general scope of the present work
is to quantify the characteristics of wall-normal and spanwise Reynolds stresses, which might be different for confined (e.g.,
pipe) and semi-confined (e.g., boundary layer) flows. In particular, the peak position of wall-normal stress and a shoulder
in spanwise stress never described in detail before are investigated using select experimental and direct numerical simulation
databases available in the open literature. It is found that the positions of the
á v¢2
ñ + \left\langle {v'{^2} } \right\rangle^{ + } -peak in confined and semi-confined flow differ significantly above δ
+ ≈ 600. A similar behavior is found for the position of the
á u¢v¢
ñ + \left\langle {u'v'} \right\rangle^{ + } -peak. The upper end of the logarithmic region seems to be closely related to the position of the
á v¢2
ñ + \left\langle {v'{^2} } \right\rangle^{ + } -peak. The
á w¢2
ñ + \left\langle {w'{^2} } \right\rangle^{ + } -shoulder is found to be twice as far from the wall than the
á v¢2
ñ + \left\langle {v'{^2} } \right\rangle^{ + } -peak. It covers a significantly large portion of the typical zero-pressure-gradient turbulent boundary layer. |
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Keywords: | |
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