In August 2012 I was approached by a dredging company with the question which head loss model to use for a project with a cutter dredge and a discharge length of 35 km.
What did the company want to know?
What were the real issues?
These questions trigerred a study in to the existing head loss models. With the knowledge that the main Dutch and Belgium dredging contractors use the Durand & Condolios (1952) and Fuhrboter (1961) models in a modified form, while companies in the USA often use the Wilson (1992) model in a modified form and in Canada the Saskatchewan Research Council model (SRC), the study started with a comparison of these models. Other models that were investigated were the Newitt et al. (1955) model, the Doron & Barnea (1987) model, the Matousek (1997) model and others. Also later models like the 4 component Sellgren & Wilson (2012) model and the 2LM and 3LM models of Wilson (1979-2014) and Matousek (1997-2014) are investigated.
Usually the models perform well in the neighbourhood of the parameters used during the experiments, especially the pipe diameter (small) and the particle diameter, but for real life conditions (large pipe diameters) the models deviate and it's not clear which model matches these conditions. Another issue is that most models are derived for transport volumetric concentrations as input and not the spatial volumetric concentrations. The research into the existing models did not give a satisfactory result.
Reason to develop a new model from scratch, the Delft Head Loss & Limit Deposit Velocity Framework. This DHLLDV Framework is based on the spatial volumetric concentration in the pipe and uniform sands or gravels and consists of a framework containing 12 sub-models.
The Limit Deposit Velocity divides particles into 5 regions. For each region different physics is used.
The 7th model transforms constant spatial volumetric concentration curves into constant transport volumetric concentration curves.
The concentration distribution is based on the LDV, since at the LDV the bottom concentration has to be the bed concentration.
The transition heterogeneous-homogeneous is at operational conditions for medium sands and requires special attention.
The bed height is also based on the LDV (bedheight zero) and on the holdup function.
The curves for graded sands or gravels are constructed by proportional summation of the curves of the different fractions after adjusting the liquid properties for the fines content.
A last addition is the influence of pipe inclination.
If you like to know more about the DHLLDV Framework, go to DHLLDV in the menu. Over time more information will be added to this website and more publications will follow.
The model is published in a book and is available on ResearchGate.
Constant spatial and delivered concentration curves for uniform and graded sands
Pipe diameters ranging from 1 inch to 1.2 m, particles of 0.5 mm
Now with Excel Workbook, see Publications.
For questions, remarks and requests contact Dr.ir. S.A. Miedema, email: email@example.com