Colloquia

Summary

Hydraulic structures, such as dikes and revetments, are often designed to allow only a minimal amount of water to pass over the top of the structure under certain wave conditions. Numerical overtopping predictions employing Volume of Fluid (VOF) methods, are considered a valuable design tool for non-standard hydraulic structures that might not be well described by empirical models. There are however, a large number of uncertainties when applying these numerical modelling techniques. This is exacerbated when modelling (semi-) permeable hydraulic structures, such as hydraulic structures constructed from rubble rock, as the flow through these permeable structures brings additional complexity.

This work investigates the potential improvements in overtopping modelling accuracy, which could be gained by simulating the flow through the armour rock voids explicitly, rather than using a porous modelling approach. In order to create a digital model of armour rock on sloped hydraulic structures, a procedural rock generation method has been developed. In combination with discrete elements modelling (DEM) simulations. This methodology can create representative armour rock layers. To what extend these generated rocks and packings reflect their physical counterparts remains a question for further research although the results shown in this work are promising. Characterization of the layer porosities has been performed with the meshed rock layer geometries and are compared to the apparent porosities measured using standard surveying techniques. The porosities obtained from the packing simulations are used directly in wave induced overtopping simulations over a simple dike geometry. The wave conditions and geometries match those of physical experiments by Chen et al. (2020) which allows for a direct comparison. Additionally, given the general tendency of overpredicting overtopping volumes by VOF methods, a number modelling effects are investigated on a smooth hydraulic structure.