Extended Spectral Proper Orthogonal Decomposition for Identifying the Correlated Structures in Building Surface Pressure and Surrounding Flow Fields

In this study, we propose a new analysis method named extended spectral proper orthogonal decomposition (ESPOD), which is a combination of the EPOD procedure and SPOD method, for identifying the correlated coherent structures in building surface pressure and surrounding flow fields. This method extracts velocity modes according to their phase synchronization with the SPOD pressure modes across the flow realizations. A case study of an isolated building reveals the main physical mechanisms of the wind forces, including the contributions of the approaching turbulence, wake vortices, and conical vortices. The results show that multiple physical mechanisms can occur at the same frequency and contribute differently to the wind forces. Therefore, neither frequency nor energy value can be used as a criterion for determining whether two structures in the velocity and surface pressure fields are caused by the same physical mechanism. However, their connection can be efficiently identified by the phase synchronization in ESPOD.