Simulations of Near-Ground Hurricane Winds Influenced by Built Structures

In this study efforts are made to improve understanding, and potentially forecasting, of near-ground hurricane winds as they interact with built structures and environments. Major landfalling hurricanes from the 2004 and 2005 seasons are simulated using a 4-km grid spacing version of the Weather Research and Forecasting (WRF) model initialized using GFS analyses. Preliminary results suggest the model's depiction of hurricane intensity is underpredicted when initialized with GFS output. A simulation of Hurricane Rita using this configuration made landfall with a central minimum pressure of 952 mb, while Hurricane Rita's measured central minimum pressure was 937 mb at landfall. As a result, wind speeds generated by WRF are less than the observed. In an attempt to improve upon these simulations, WRF Three-Dimensional Variational Data Assimilation (3DVAR) will be used to assimilate observations taken near the model initialization time.

Upon landfall, vertical wind profiles will be extracted from WRF model output near coastal regions that are encompassed by the region of highest forecasted wind speeds. These profiles will be used to initialize a three-dimensional wind tunnel domain in Fluent, a computational fluid dynamics (CFD) solver for numerically simulated complex flows. Contained within the wind tunnel are several structure configurations of interest, including a single building, parallel buildings, a suburban array, and a city environment. The wind tunnel and built structures can be created using the Fluent preprocessor, Gambit, while Fluent is used to resolve the microscale flow patterns. To simulate the effect of time which would result in changing wind directions, the structures will be rotated within the tunnel domain. Distributions of wind velocities at various elevations within close proximity of the structures will be presented