Modelling of open filters under wave loading

Permeable coastal structures that consist of rock typically contain granular filters. The internal transitions between two layers are normally geometrically tight to prevent material washout. Applying open filters with only minimal loss of material through the layer above, may be a cheaper alternative (see also Van Gent and Wolters, 2015). Physical model tests have been performed for rather open transitions between the armour and underlayer. A numerical model that is capable of modelling the transport of sand underneath layers of rock has been applied here on the tested structure geometries to analyse the potential of an open transition between sand and the layer of rock above (without geotextile). In addition, one of the tested configurations where transport of material from the underlayer into the armour layer occurred, has been modelled numerically.