External Transient Flow Around Tall Buildings

Description

This case study uses ANSYS Fluent to model wind flow around a cluster of three buildings, a canonical bluff-body aerodynamics problem central to architectural and structural wind engineering. Understanding how wind interacts with building masses is essential for façade load design, pedestrian wind comfort assessments, and site planning around tall structures. A 5 m/s horizontal airstream is directed at the building group to study wake formation and vortex shedding behavior downstream.

Methodology

The simulation is transient, run for 1 s with a 0.01 s time step, using a pressure-based solver. The computational domain, built in DesignModeler, is a 120 m × 300 m × 100 m rectangular volume containing three 75 m tall buildings — representative of a mid-to-high-rise urban block. The domain was meshed in ANSYS Meshing using an unstructured grid of 128,893 elements, with local refinement around the building surfaces to resolve near-wall flow gradients and boundary layer effects accurately.

Conclusion

Output includes pressure and velocity contours, turbulent kinetic energy (TKE), pathlines, and velocity vector fields, all evaluated at the final time step (t = 1 s). Peak pressure occurs on the windward façades, where incoming flow first impinges — directly relevant to cladding and structural load estimation in building design. Leeward wakes show clear vortex formation, illustrating the kind of turbulent recirculation zones that inform pedestrian-level wind comfort and building-spacing decisions in architectural planning.