Height and wave length of alternate bars in rivers: modelling vs. laboratory experiments


Knaapen, M.A.F. and Hulscher, S.J.M.H. and Vriend, H.J. de and Harten, A. van (1999) Height and wave length of alternate bars in rivers: modelling vs. laboratory experiments. [Report]

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Abstract:Alternate bars are large wave patterns in sandy beds of rivers and channels. The crests and troughs alternate between the banks of the channel. These
bars, which move downstream several meters per day, reduce the navigability of the river. Recent modelling of alternate bars has focused on stability
analysis techniques. We think, that the resulting models can predict large rhythmic patterns in sandy beds, especially if the models can be combined
with data-assimilation techniques. The results presented in this paper confirm this thought.
We compared the wavelength and height of alternate bars as predicted by the model of Schielen et al. [14], with the values measured in several flume
experiments. Given realistic hydraulic conditions R Re > 2*10³, (R the width-to-depth ratio and Re the Reynolds number), the predictions are in good
agreement with the measurements. In addition, the model predicts the bars measured in experiments with graded sediment. If R Re < 2*10³, the agreement
between model results and measurements is lost. Thewave height is clearly underestimated, and the standard deviation of the differences between
predictions and measurements increases. This questions the usefulness of small flume experiments for morphodynamic problems.
Item Type:Report
Additional information:Civil Engineering and Management research report 99W-008/MICS-004
Engineering Technology (CTW)
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Link to this item:http://purl.utwente.nl/publications/21334
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