CFD Modeling for the Analysis of Living Shoreline Structure Performance

A set of 9 artificial oyster reef products were proposed for use in an erosion control project in coastal Louisiana with the goal of reducing shoreline retreat and providing ecosystem benefits through creation of a platform for oyster growth, thus creating a living shoreline. Performance characteristics of available artificial oyster reef products are limited due to the experimental nature of the products. Their performance in terms of wave energy reduction and unit stability are generally poorly understood with available data. Due to the large number of different units, potential variability in unit geometry, and high costs for physical modeling, the artificial oyster reef structures were analyzed using the 3-D volume of fluids CFD model FLOW3D, with 3D structure models integrated into the model. The structures tested included a typical low-crested rock breakwater for the purpose of model wave transmission validation, as well as fixed and floating concrete precast units. A range of wave conditions were tested and the results of interest included wave transmission over/through the structures, as well as hydrodynamic loads on the structures for use in design. The CFD modeling was performed in a manner analogous to a full scale laboratory experiment with sufficient units included to capture variability in wave transmission along the length of the structure. Modeling results were used to evaluate wave energy reduction performance, hydrodynamic stability, and as part of an evaluation of artificial oyster reef overall cost-effectiveness.