Comparing the impacts of geometry level of detail in computational wind engineering with on-site urban measurements

Abstract

Urbanization has led to more than half of the world’s population living in cities. The design of sustainable and resilient urban environments is becoming increasingly critical to optimize the well-being of their inhabitants and the planet. One of the major challenges in achieving this is the complex wind flow patterns in densely built-up areas, which require accurate prediction and analysis to effectively harness the potential benefits of wind flow, such as natural ventilation and wind power generation. However, the unique features of urban landscapes, such as high-rise buildings, narrow streets, and irregular building shapes, make the analysis of wind flow within urban canopies complicated.

In recent years, Computational Fluid Dynamics (CFD) has become a vital tool for studying wind flow in urban areas. Still, the complex geometries of buildings can lead to challenges, including recirculation, reattachment, intense turbulence, and dead zones. Moreover, vegetation plays a crucial role in controlling wind flow in dense areas by acting as a physical barrier, significantly reducing the wind speed and alter the wind flow direction. Additionally, generating geometry for computa-tional fluid dynamics (CFD) simulation in complex urban environments is a chal-lenging and time-consuming process.

Hence, for this thesis, the City4CFD software will be used to automatically recon-struct a 3D model of Stanford University at LoD1.2, which will significantly reduce the time and effort required to generate the complex geometry necessary for com-putational fluid dynamics (CFD) simulations in urban environments. The results will be compared to those obtained from an already manually reconstructed model at LoD2.1 and real-world measurements conducted within the area of interest. This will allow me to determine the differences introduced by different level of detail.

The research will address several sub-questions, such as the steps needed to auto-matically reconstruct a 3D city model, the potential improvements in simulation accuracy by increasing LoD, and the impact of complex geometries on wind flow. The results of the thesis indicated that a more complex geometry Level of Detail (LoD) can enhance the accuracy of simulations by providing a more precise de-piction of wind flow patterns. In other words, a higher LoD geometry, such as LoD2.1, can more accurately predict wind patterns in urban environments based on real-world measurements. The study observed that the LoD2.1 model, which in-corporates more complex features, generated simulation outcomes that were closer to the measurements compared to the less detailed LoD1.2 model.