CFD Numerical Simulations to Comprehend the Wind Speed-ups Produced by the Geomorphic Complexity of Puerto Rico

The 2017 Atlantic hurricane season caused unprecedented levels of property and environmental damage in coastal and rural areas across the Caribbean and the continental USA. Most of the damage was caused by storm surge and high wind speeds. Previous studies indicate that wind approaching sharp changes in ground elevation increases damages in low-rise constructions, owed to wind speed-up. For this reason, a study to create Puerto Rico’s Special Wind Region Maps was funded by the Federal Emergency Management Agency (FEMA). Wind speed-up data was developed through a wind tunnel study of six regions of the Island’s topography at a scale of 1:3100; performed by Dr. Forrest Masters at the University of Florida and Dr. Peter Vickery form Applied Research Associates (ARA). Results were used to helped created speed-up model for the entires island employing an empirical model that was calibrated with the wind tunnel data. The ASCE 7 standards and building codes are used by civil engineers, as it provides technical guidelines for promoting safe infrastructure designs. Practitioner Structural and Wind Engineers employ wind speed maps, in conjunction with the ASCE 7 analytical method, to calculate pressures and wind loads on structures. However, since ASCE 7 speed-up factors were developed for isolated landforms, it is not accurate for Puerto Rico’s complex terrain. For such regions, numerical modeling is one of the best tools to assess the geomorphic effects on the airflow. Hence, a three-dimensional computational fluid dynamic (CFD) numerical model was implemented to perform wind simulations using OpenFOAM^®. Wind simulations over the terrain of the island of Culebra were performed with steady wind flows approaching from all sixteen compasses directions. The numerical model wind speed-up factors were compared with University of Florida wind tunnel studies. Wind profiles for each location were mapped and analyzed to understand better the airstream speed-up triggered by the topographic features and how they vary along with atmospheric boundary layers. The CDF model data help to fill the gap and limitations from the wind tunnel studies like the speed-up attenuation in the vertical profile. This effort will help to validate the first wind maps for Puerto Rico developed by ARA.