Complex wind force attribution under aerodynamic interference between two buildings

This study applied the extended spectral proper orthogonal decomposition technique to identify key flow mechanisms impacting wind forces under aerodynamic interference. The method initially extracted the most influential components from the surface pressure fields that contribute to wind force fluctuations and then identified the corresponding velocity-field components that synchronize phase fluctuations with the pressure components in the frequency domain. This approach provides an intuitive interpretation of the complex wind force spectra by quantifying the energy contributions from various flow mechanisms and visualizing them through both the velocity and pressure components extracted from turbulent flow. The method was applied to both isolated-building and two-building cases to study the interference effect. Based on the decomposition, the most impactful components of the approaching turbulence on the surface pressure of the isolated building model were unveiled, whose direction coincided with the direction of the gap flow between the two building models. This overlap could potentially explain the significant increase in the variance of wind forces. The study also observed substantial interference-induced modifications in wake vortices. These vortices expanded considerably in size and decreased in frequency compared to those in the isolated-building scenario. The across-wind moment of the upstream building model was largely independent of wake vortex shedding, suggesting that other flow mechanisms could potentially become dominant when wake vortices are significantly suppressed due to aerodynamic interference. This study offers comprehensive insights into the complex dynamics of wind forces under aerodynamic interference.