Individual overtopping events at dikes

Recently, formulae have been derived for maximum flow depths and velocities on the crest and inner slope of dikes or levees at wave overtopping. Two independent physical model test programs in different wave flumes showed, however, a large difference in the results. The present paper clarifies this discrepancy and shows that the empirical...

Interface stability of granular filter structures under currents

Granular filters are used for protection of structures against scour and erosion. For a proper functioning it is necessary that the interfaces between the filter structure, the subsoil and the water flowing above the filter structure are stable. Stability means that there is no transport of subsoil material through the filter to the water above...

Erosion at transitions in landward slopes of dikes due to wave overtopping

Destructive wave overtopping tests have been performed at more than 20 dike sections in the Netherlands using the Wave Overtopping Simulator to simulate the overtopping waves. The tests show the combined behaviour of turf and substrate up to mean wave overtopping discharges of 75 ?/s per m, meaning wave volumes up to 5,500 ?/m with flow...

The influence of upstram turbulence on local-scour holes

Excessive local scour can progressively undermine the foundation of a structure. Because complete protection against scour is too expensive generally, the maximum scour-depth and the upstream slope of the scour hole have to be predicted to minimize the risk of failure. In 1961 a systematical research 'tY'ith respect to scour holes started in the...

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Two-dimensional mathematical modelling of local-scour holes

Jet scour

This paper discusses scour without bed protection, such as propeller scour, two-dimensional horizontal, three-dimensional horizontal scour generated by free jets downstream of gates and outlets, two-dimensional vertical and three-dimensional vertical scour. The flow velocities in two- and three-dimensional propeller and free jets are briefly...

Local Scour: Flow simulation by the 2-D turbulent model ODYSSEE

The general purpose of this research project is to model mathematically the local scour downstream of a structure (2-D). The model has to simulate the development of the scour as a function of the time. Basically two models are necessary namely a flow model and a morphological model. The latter model has to describe the bed and suspended load...

Local Scour: Damping of turbulence parameters in relaxation zone

The general purpose of this research project is to model mathematically the scour-hole downstream of a structure (2-D). The model has to simulate the development of the scour as a function of time. Basically two models are necessary namely a flow model and a morphological model. The latter has to describe the bed- and suspended load and the...

Local Scour: Influence of an exponential eddy viscosity distribution on the longitudial flow velocity

The general purpose of this research project is to model mathematically the local scour downstream of a structure (2-D). The model has to simulate the development of the scour as a function of the time. Basically two models are necessary namely a flow model and a morphological model. The latter model has to describe the bed and suspended load...

Lokale ontgronding. Analyse geparametriseerd waterbewegingsmodel 'Profielenmethode'

Het algemeen doel van het onderzoek lokale ontgronding is het numeriek modelleren van ontgrondingskuilen als functie van de tijd (twee dimensionaal vertikaal). Het model moet bij gegeven initiele stroomcondities en berekende materiaaleigenschappen de configuratie van de ontgrondingskuil na een bepaalde tijd simuleren. Hiertoe zijn twee modellen...

Users manual: DUCT-SUSTRA

Some information is given how to use the scour model DUCT-SUSTRA (Hoffmans, 1991). The scour model predicts the morphological process in scour holes or trenches and consists of two separated sub-models: a flow model DUCT and a morphological model SUSTRA. The flow model is based on the equation of continuity and the momentum equations for...

Local Scour: Flow model with prescribed eddy viscosity

A two dimensional mathematical model DUCT, which is based on a parabolic boundary layer technique, using finite elements, is proposed to predict the flow and turbulence field in complicated geometrical conditions, where recirculating flow may occur. Numerical results of the DUCT-model are compared with k-eps-predictions as well as laboratory...

Concentration and flow velocity measurements in a local scour hole

Flume experiments with small Froude numbers have been carried out to study the concentration field in a local scour hole without supply of sediment load. The measuring results will be used to check the validity of the two dimensional scour model DUCT-SUSTRA. The objective of the experiments was to measure the concentrations at various locations...