Comparison of different urban climate modelling tools for predicting pedestrian thermal comfort

Estimating pedestrian thermal comfort in urban settings is crucial for climate adapted planning of buildings and districts. Practitioners and urban planners are increasingly relying on simulation tools to assess the local thermal conditions in projects. Simulation tools are now widely available, however, performance comparisons between tools are rare regarding computational load and accuracy. This makes it difficult to choose the optimal tool for a certain urban planning project considering urban heat mitigation.

In this study, to specifically assess performance of the most relevant simulation tools for pedestrian thermal comfort, we present a benchmark case  comparing simple microclimate models (SMM) and all-physics microclimate models (AMM). As SMM we consider SOLWEIG which does not use complex CFD solving of the flow around buildings. As AMM codes we consider urbanMicroclimateFoam, developed by the authors, PALM and ENVI-met, all resolving the flow around buildings based on different CFD turbulence models among other differences in their modeling approaches. The benchmark case is based on an idealized geometry of an isolated street canyon. Simulation conditions are harmonized as much as possible between the different tools. The comparison focuses on heatwave conditions.

Based on the results and workflow, the authors make suggestions for using these tools in research and practice.