CFD in Urban Aerodynamics: Wind Speed Conditions in Passages between Parallel Buildings

Abstract

CFD simulations of the wind speed conditions in passages between generic parallel building configurations are performed. CFD validation is conducted based on published wind tunnel data. The computational results agree well with the experimental data when an appropriate grid resolution is employed. The required grid resolution across the passage width appears to be a function of the passage width and the building influence scale. A grid resolution guideline is provided. Finally, the simulations and the measurement data are used to identify three different types of passage flow as a function of the dimensionless ratio of passage width to building influence scale. Computational Fluid Dynamics (CFD) is increasingly being used to address problems in Urban Aerodynamics. While the practical applicability of DNS (Direct Numerical Simulation) will not be established in the near future, the RANS approach (Reynolds-Averaged Navier-Stokes) and the LES approach (Large Eddy Simulation) have become powerful tools in addressing a variety of flow problems in the urban environment, ranging from pollutant dispersion over pedestrian wind nuisance to winddriven rain studies. Successful application of RANS or LES for complex urban environments is based on the successful application of these approaches for the different sub-configurations present in the urban environment, e.g. passages between buildings. Urban Aerodynamics simulations generally involve large computational domains with many computational cells or control volumes. Knowledge of the flow behavior and of the subsequent minimal grid resolution requirements for the sub-configurations is important to arrive at optimal mesh resolutions and accurate and economical simulations for the urban environment as a whole. One of the most common sub-configurations is a passage between two parallel buildings. In the past, CFD for wind speed in passages between buildings has been conducted by many authors. For the specific situation of wind flow parallel to the passage between two generic buildings of equal height however, relatively few numerical studies have been made. In particular, grid resolution guidelines are limited. In a recent comprehensive publication of recommendations for CFD simulations of the