Influence of building surface solar irradiance on environmental temperatures in urban neighborhoods

For buildings located in actual urban neighborhoods, modeling of outdoor airflow with Computational Fluid Dynamics (CFD) requires solar radiation at building surfaces to predict local environmental temperatures. This study conducts a parametric analysis to support the development of coupled simulations of outdoor airflow and solar radiation simulations at building surfaces. To account for different assumptions used in the outdoor modeling, this study uses OpenFOAM CFD and couples it with three different simulation engines, including EnergyPlus, Daysim, and Radiance to predict simulated outdoor solar irradiance for implementation in outdoor CFD simulations. The primary aim of selecting these three simulation engines is to evaluate tradeoffs between the model complexity and accuracy for simulated outdoor solar irradiance for outdoor CFD simulations. Examined parameters include: (i) surface representation with different mesh types, (ii) urban plan area density, and (iii) the impact of simulated solar irradiances on the simulated air temperature and velocity values in the CFD simulations. The study results showed that the surface representation has up to a 7.6% and 133% influence on the simulated outdoor global and local solar irradiances, respectively. The surface thermal boundary conditions have up to 1.5 °C difference on the air temperature and negligible impacts on the air velocity.