Narrow Results

Wave impact on one and two structural beams with rectangular cross section is simulated with a two-dimensional finite volume method, solving the unsteady Euler equations and employing a VOF-type method for the description of the free surface. Four different test series are carried out, each corresponding to a wave impact scenario in the experimental database of Sterndorff [2002]. For the case of wave impact on a single structural element the numerical results show good agreement with measured force time histories. In the computations featuring two beams, the prediction of the shadowing effect of the first beam on the second is in reasonable agreement with the experimental data. However, the force peak on the second beam is somewhat over-predicted. The calculations successfully predict a second peak in the force time series of the second beam, which is caused by airborne water shipped over the first beam. Throughout the work, spurious spikes of very short duration appear in the computed load time series, originating from the changing of the flow separation location along the lower edge of the beams.

A combined model was built of three main modules based on the Volume of Fluid (VOF) method, Discrete Element Method (DEM), and Finite Element Method (FEM). It was proposed to utilize this model to simulate the deformation of the rubble mound and the sandy bed due to surface wave action. The model included the full interaction between wave motion with free surface and replaceable separate particles of the rubble mound. Momentary arrangement of the fluid, particles and resulting permeability was tracked within a domain of time and two-dimensional space by maintaining cyclic data transfer between the three method modules. A new technique of porosity adjustment was presented. The model results were compared to small-scale laboratory test results. Based on the comparison, the VOF-DEM-FEM model appeared to be a promising tool to handle the destruction process of the rubble coastal structures built on a permeable bottom.