Field testing and CFD LES simulation of offshore wind flows over coastal dune terrain in Northern Ireland

The role of offshore-directed winds in aeolian sand transport over and along coastal dune systems is studied under a project funded through the UK’s Natural Environment Research Council (NERC) “Responsive Mode Program”. The field study area is a 6km beach located at Magilligan Strand, Northern Ireland. The coastline has a northeastern-facing orientation on the margin of the Atlantic Ocean and forms the seaward edge of a large vegetated Holocene (5-6000 yrs BP) cuspate foreland. Landward of the beach/foredune crest, a series of 15-20m high vegetated dune ridges are located parallel to the shore. A component of this research program is the measurement of the wind flows over and across the dune and beach terrain and comparison with Computational Fluid Dynamic simulation results Detailed wind flow measurements were obtained during field testing in September 2009 using an extensive array of mast mounted three-dimensional ultrasonic anemometers. Large Eddy Simulation (LES) was performed of the wind flow over the terrain using the open-source CFD software OpenFOAM. The computational domain and mesh includes the terrain obtained by high resolution LIDAR measurements with localized mesh refinement near the complex terrain. The paper illustrates the comparison between the measured and simulated wind flow characteristics. The discussion also includes early commentary on how the new insights into the windflow characteristic inform study of the evolution of coastal dune geomorphology.