Near-critical free-surface flows: real fluid flow analysis |
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Authors: | Oscar Castro-Orgaz Hubert Chanson |
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Institution: | (1) Professor in Civil Engineering, The University of Queensland, Brisbane, QLD, 4072, Australia |
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Abstract: | An open channel flow with a flow depth close to the critical depth is characterised by a curvilinear streamline flow field
that results in steady free surface undulations. Near critical flows of practical relevance encompass the undular hydraulic
jump when the flow changes from supercritical (F > 1) to subcritical (F < 1), and the undular weir flow over broad-crested
weirs where the flow changes from subcritical (F < 1) to supercritical (F > 1). So far these flows were mainly studied based
on ideal fluid flow computations, for which the flow is assumed irrotational and, thus, shear forces are absent. While the
approach is accurate for critical flow conditions (F = 1) in weir and flumes, near-critical flows involve long distances reaches,
and the effect of friction on the flow properties cannot be neglected. In the present study the characteristics of near-critical
free-surface flows are reanalysed based on a model accounting for both the streamline curvature and friction effects. Based
on the improved model, some better agreement with experimental results is found, thereby highlighting the main frictional
features of the flow profiles. |
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Keywords: | |
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