Application of the SANTOSS sand transport model to irregular oscillatory flows

Gerwen, Wietse van (2014) Application of the SANTOSS sand transport model to irregular oscillatory flows.

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Abstract:The SANTOSS sand transport model can predict the net sand transport for various wave and oscillatory flow conditions. The model was originally developed for regular flow conditions. New research is looking into sand transport processes under breaking- and irregular waves. A way of properly modelling irregular conditions is not determined yet but the SANTOSS model could be used as basis. The goal of this research is therefore to assess the ability of the SANTOSS model to predict sand transport rates for irregular oscillatory flows. The main question is how the model could be used for irregular flows. For this two methods are tested. The wave-by-wave method treats every individual wave in an irregular group as an individual wave. For every individual wave in the group the transport is calculated after which the mean of all transports in the group is taken to yield the predicted net transport rate. The representative wave method describes an irregular flow with single parameters. How these parameters are defined has a great influence on the calculated transport. It has been found that skewness factors weighted to their corresponding representative velocity for every wave in an irregular group works well. For the representative velocity the fifty or sixty percent significant value gives the best predictions. However, this depends on the way the measured velocity time series are pre-processed in terms of smoothing. The conclusion is that the representative wave method is the best way of describing irregular waves if you want to predict the transport with SANTOSS. Both the wave-by-wave method and the representative wave method perform equally well, most predicted transports are within a factor two of the measured transport. But with the representative wave method no adaptations to the model need to be made. A recommendation for improving the model is to find a way of better predicting ripple dimensions in the transition stage from the ripple regime to the sheet flow regime. The model performs very poor in this stage, especially for larger grain sizes.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
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