Numerical Simulations of the Urban Microclimate

Licentiate thesis, 2023

As global urbanization is accelerating and the majority of the world's population continues to reside in cities, sustainable urban development is becoming increasingly crucial. Evaluation of the urban microclimate is a vital aspect of planning sustainable cities, as it can significantly impact on the health and comfort of urban residents. Computational Fluid Dynamics is a cost-effective and flexible tool to predict microclimate conditions, although often not utilized in the urban planning process until the final stages of a project due to complex pre-processing. The current practice of urban planning also often involves simulating different physical phenomena in separate tools, making it difficult to understand the interaction. This thesis presents the potential of the numerical immersed boundary framework IBOFLow as a tool for urban planners to evaluate the urban microclimate at the early stages of the design processes. The complex and time-consuming pre-processing of urban regions is eliminated using automatically generated Cartesian octree grid meshes where the complex geometries are represented by the immersed boundary methodology. The framework is validated for wind using wind tunnel experiments and compared to a commercially used software to show the importance of including the complex local terrain to generate realistic results. Finally, initial results of the heat simulations are covered to visualize the idea of IBOFlow as a means to simulate the urban microclimate at large, including all necessary physics.