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Engineering LibreTexts

1.4: The Delft Head Loss and Limit Deposit Velocity Framework

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  • In the following chapters the different models from literature will be analyzed, leading to a new integrated model based on a new classification of the flow regimes. This new model is named the Delft Head Loss & Limit Deposit Velocity Framework (DHLLDV Framework). The Framework is integrated in a way that all flow regimes are described in a consistent way showing the transition velocities. The model is validated by many experiments from literature and experiments carried out in the Delft University Dredging Engineering Laboratory for particles ranging from 0.05 to 45 mm, pipe diameters ranging from 0.0254 to 0.9 m and relative submerged densities ranging from 0.24 to 4 ton/m3. The model does not just give hydraulic gradient relations, but also Limit Deposit Velocity relations, slip ratio relations (the relation between the volumetric spatial concentration and the volumetric delivered concentration), bed height relations and a concentration distribution model. The Framework also gives a tool to determine the influence of the grading of the sand or gravel. The starting point of the model is a uniform sand or gravel and a constant volumetric spatial concentration. Based on the hydraulic gradient and slip ratio relations, the volumetric delivered concentration hydraulic gradient relations are derived. The latter is very important for practical applications.