Evaluation AC4-02
Flow and Sediment Transport in a Laboratory Model of a stretch of the Elbe River
Application Challenge 4-02 © copyright ERCOFTAC 2004
Comparison of Test data and CFD
Fig. 2 compares calculated and measured surface-velocity distributions at various cross-sections indicated in Fig. 1. The agreement is reasonably good and the results follow general trends for curved rivers, i.e. the maximum velocity at cross-sections 1 to 4 is close to the left, outer bank in the first bend while the maximum velocity at cross-sections 7 and 8 is close to the right bank which is now the outer bank in the second bend. Fig. 3 compares calculated and measured morphology of the channel bed after 6 hours starting from a flat bed. Again the calculation results agree generally with the experiments, with point bars and scour channels forming in the curved section. Fig. 4 allows a more quantitative comparison as here the measured and calculated bed profiles are compared at 6 cross-sections. The model reproduces well the development of a scour channel near the outer left bank in the initial bend and the change-over to a profile with a scour channel on the other side in the downstream region where the bend is in the other direction. Hence, altogether satisfactory results could be achieved in these calculations and the main assessment parameters could be reproduced fairly well. It should be remembered that there is some uncertainty about the specification of the non-equilibrium adaptation length Ls in the bed-load model, which was set equal to the mesh size, and further studies should be carried out on the sensitivity of the results to this parameter.
Fig.2 Comparison of the surface velocity between the calculation and experiment.
Fig. 3 Comparison of the river bed morphology between the calculation and experiment
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Fig. 4 Comparison of bed profiles between calculation and experiment
© copyright ERCOFTAC 2004
Contributors: Wolfgang Rodi - Universität Karlsruhe
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