Flow and scour around a vertical cylinder exposed to current are investigated by using a three-dimensional numerical model based on incompressible Reynolds-averaged Navier–Stokes equations. The model incorporates (i) k - ω turbulence closure, (ii) vortex-shedding processes, (iii) sediment transport (both bed and suspended load), as well as (iv) bed morphology. The influence of vortex shedding and suspended load on the scour are specifically investigated. For the selected geometry and flow conditions, it is found that the equilibrium scour depth is decreased by 50% when the suspended sediment transport is not accounted for. Alternatively, the effects of vortex shedding are found to be limited to the very early stage of the scour process. Flow features such as the horseshoe vortex, as well as lee-wake vortices, including their vertical frequency variation, are discussed. Large-scale counter-rotating streamwise phase-averaged vortices in the lee wake are likewise demonstrated via numerical flow visualization. These features are linked to scour around a vertical pile in a steady current.

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This paper discusses a parameter based coastal vulnerability assessment model to sea level rise. The model integrates physical characteristics and human activities with expert perception through an application of analytical hierarchy process (AHP). The results of AHP enables users to assign weights to parameters of the model which determine vulnerability of a coastal area to the impacts of sea level rise such as coastal erosion, inundation, flooding due to storm surges, saltwater intrusion to groundwater and rivers. The results of AHP also indicates that sea level rise is not considered as one of the main driving forces of the impacts that might be already present contrary to the reports that state that sea level rise will trigger many problems along coastal areas. The application of the coastal vulnerability assessment model to two different coastal areas of Turkey showed that there is a need for overall evaluation of coastal areas in terms of vulnerability to sea level rise considering all the impacts. It is seen that assessing overall vulnerability is an important tool for national assessments. On the other hand, impact vulnerabilities are important when regional to local planning are considered since a region having a low overall vulnerability might show higher vulnerability for individual impacts. The proposed vulnerability methodology integrated with expert perception enables a simple yet effective representation of the coastal system while enabling decision makers to come up with proactive adaptation measures.

This study presents a three-dimensional (3D) numerical modeling study on the backfilling process around monopiles. The numerical model utilized in the study is based on that given by Jacobsen (2011). It is composed of two main modules. The first module is the hydrodynamic model where the fluid flow conditions around the structure and near the bed are solved. The second module is the morphologic model where the sediment transport rates over the bed and around the structure are obtained and used in updating bed elevations around the structure. In the numerical model, the hydrodynamic computations are followed by morphologic computations, resulting in updated bed elevations and mesh structure which are again used to update the hydrodynamics for the next time step. In the hydrodynamic model, Reynolds-averaged Navier-Stokes (RANS) equations are solved with a k-ω turbulence closure. The morphologic model comprises five sub-modules, namely bed load, suspended load, sand slide, bed evolution and 3D mesh motion. The model is constructed in OpenFOAM CFD Package. The present model is applied to several problems of backfilling around a monopile by waves only, where the initial scour hole is generated by steady current. The numerical results appear to be in accord with the existing experimental information.