Two and three dimensional numerical airflow modelling along forest edges

Wind – tree interactions can be catastrophic and lead to either the structural or rooting failure of trees. These failures have been identified along forest-clearing boundaries where increased wind and turbulence patterns exist. The increasing cost of field and wind tunnel observations to study airflow in forests has prompted the investigation of alternative techniques. In this study, airflow was modelled using FLUENT, a computational fluid dynamic (CFD) program. The FLUENT modelling was validated using wind tunnel measurements from Novak et al. (2001). A flow domain, similar to the University of British Columbia wind tunnel, was created for FLUENT, complete with bluff bodies, large and small roughness elements including a large number of tree shaped geometries. The canopy of the trees were defined as porous to mimic airflow through real trees. Turbulence was parameterized using three variations of the κ-ε turbulence model: the standard κ-ε model, the realizable κ-ε and the Renormalized Group theory (RNG) κ-ε. Simulations were performed on an SGI Origin 3400 28 processor computer at the University of Northern British Columbia. The unsteady flows were simulated at a rate of 10000 Hz for 1.51 seconds. The model results were compared with wind tunnel observations using the root mean square error and Willmott d statistic calculated at 29 vertical points from ten horizontal locations. The results suggest that FLUENT has skill in replicating wind tunnel measurements of airflow past trees.