In this paper we use the Computational Fluid Dynamics (CFD) toolbox OpenFOAM to perform numerical simulations of multiple floating point absorber wave energy converters (WECs) arranged in a geometrical array configuration inside a numerical wave tank (NWT). The two-phase Navier-Stokes fluid solver is coupled with a motion solver to simulate the hydrodynamic flow field around the WECs and the wave-induced rigid body heave motion of each WEC within the array. In this study, the numerical simulations of a single WEC unit are extended to multiple WECs and the complexity of modelling individual floating objects close to each other in an array layout is tackled. The NWT is validated for fluid-structure interaction (FSI) simulations by using experimental measurements for an array of two, five and up to nine heaving WECs subjected to regular waves. The validation is achieved by using mathematical models to include frictional forces observed during the experimental tests. For all the simulations presented, a good agreement is found between the numerical and the experimental results for the WECs’ heave motions, the surge forces on the WECs and the perturbed wave field around the WECs. As a result, our coupled CFD–motion solver proves to be a suitable and accurate toolbox for the study of fluid-structure interaction problems of WEC arrays.

Long-term changes in dune volume at the Belgian coast are analyzed based on measured data by airborne surveys available from 1979. For most of the 65 km long coastal stretch, dune volume increases linearly in time at a constant rate. Dune growth varies between 0–12.3 m³/m/year with an average dune growth of 6.2 m³/m/year, featuring large variations in longshore directions. Based on a wind data set from 2000–2017, it is found that potential aeolian sediment transport has its main drift from the west to southwest direction (onshore to oblique onshore). Based on a modified Bagnold model, onshore potential aeolian sediment transport ranges to a maximum of 9 m³/m/year, while longshore potential aeolian sediment transport could reach up to 20 m³/m/year. We found an important correlation between observed and predicted dune development at decadal timescales when zones with dune management activities are excluded. Most of the predicted data are within a factor of two of the measured values. The variability in potential transport is well related to the variability in dune volume changes at the considered spatial–temporal scale, suggesting that natural dune growth is primarily caused by aeolian sediment transport from the beach. It also suggests that annual differences in forcing and transport limiting conditions (wind and moisture) only have a modest effect on the overall variability of dune volume trends.

In the framework of the reorganisation of several historical wet deposits of a chemical processing plant, one of the oldest wet deposits was cleared because of environmental and economic considerations. The stored sludge (around 350 000 m3) was transported to the neighbouring environmentally controlled deposit, Veldhoven (Ham, Belgium), and stacked on top of existing sludge, using the sludge itself as dyke construction material. To calibrate the embankment stability analysis procedure, a full-scale slope failure test was conducted on an embankment built with industrial calcium fluoride (CaF2) sludge. The Norwegian Geotechnical Institute–active, direct simple shear, passive (NGI–ADP) material model was used to perform a finite-element back-analysis of the full-scale slope failure test. Anisotropic conversion factors are suggested to convert the in situ measured vane shear strengths to shear strengths at different anisotropic stress states, which can then be implemented in the NGI–ADP model. The simple and quickly executable in situ vane shear test was used to master the uncertainties linked to the heterogeneity of the sludge. Sludge heterogeneity not only depends on sludge composition, but also on manipulations during transport and handling of the sludge at the construction of the elevations. The results of the full-scale slope failure test support the proposed modelling of the embankment stability problem.