CFD Modeling and Simulation Guidelines - City of London

ArchiWind’s Commitment to Quality

At ArchiWind, we strive to provide innovative solutions using the latest technology. Our team blends research and industry knowledge to bring scientific accuracy to your processes. We ensure our work complies with all regulations. ArchiWind’s simulations are crafted to meet the City of London Wind Microclimate Guidelines, guaranteeing reliability and compliance.

“Computational fluid dynamics (CFD) tools can create high-quality output that provides a good understanding of fundamental flow features. However, significant variability in methodology can exist between different CFD methods and care should be taken to ensure that appropriate modeling approaches are used.”

CFD Modeling Guidelines

Detailed 3D Representation

• Proposed Development: The CFD models must include a detailed three-dimensional representation of the proposed development.
• Building Features: Features that project more than 0.5m near pedestrian areas can affect localized wind conditions and must be modeled for both the proposed and existing buildings around the site.
• Entrances and Pedestrian Areas: Building geometry near entrances and key pedestrian areas should be included in the models as they could affect the results.

Landscape Features

• Baseline Wind Studies: It is prudent to ignore landscape features smaller than 8m in height in baseline wind studies. Large mature trees can be included, but guidance for modeling these features is limited, so a conservative interpretation of their impacts is necessary.

Meshing Guidelines

• Maximum Cell Sizes: Cell sizes near critical locations (e.g., entrances, corners) must be 0.3m or smaller. Ensure at least 10 cells across a street canyon.
• Efficiency: Cell sizes for buildings away from the target can be larger to allow for modeling efficiency.

Surrounding Buildings

• Modeling Radius: The CFD models should represent all surrounding buildings within 400m of the center of the site.
• Influential Buildings: Include taller buildings outside this zone if they could influence wind conditions within the project site, especially for wind directions where they are upwind.

Near-Ground Effects

• Prism Layers: The models must contain at least 3 prism layers below 1.5m height to capture near-ground effects.
• Turbulence Models: Avoid using the standard k-epsilon model or 0 or 1 equation models. The realizable k-epsilon model is a robust industry standard, and other models such as k-omega SST can be used if the mesh is suitable.

Reporting and Cumulative Effects

• Cumulative Effects: CFD analysis should report conditions in areas away from the site where clusters of tall buildings could lead to adverse wind conditions.
• Consultant Awareness: Wind consultants should be aware of expected wind conditions around other cumulative or existing high-rise buildings by reviewing publicly available planning reports on the City of London planning portal.