Turbulence-induced ventilation of an isolated building: Ventilation route identification using spectral proper orthogonal decomposition

Abstract

Turbulence dominates the natural ventilation of a building when openings are parallel to the external wind, and multiple factors associated with turbulence simultaneously affect natural ventilation. This study applies spectral proper orthogonal decomposition (SPOD) to quantitatively identify the main ventilation routes produced by turbulence in an isolated building with two symmetric openings. The turbulence data are obtained from large-eddy simulations of various wind directions and window casements. Two major turbulence-induced ventilation mechanisms are observed when the wind is parallel to the openings: The first is in the low-frequency region and is characterized by a slight change in the wind direction of the external flow, which contributes to cross ventilation. The second is in the high-frequency region and is characterized by a flow separation on the side of the building, which contributes to single-sided ventilation. The ventilation routes are visualized using SPOD modes and animations. In addition, the impact of window casements on turbulence-induced ventilation is investigated. The installation location of the window casements can either enhance or weaken the cross ventilation depending on whether the turbulence is efficiently utilized in the ventilation and can significantly affect the indoor cross ventilation route. However, regardless of the side that they are installed on the window, the casements may slightly improve single-sided ventilation by limiting the occurrence of separated eddies near the openings. • Visualization of turbulence-induced ventilation in an isolated two-opening building. • Quantitative analysis of the contributors to natural ventilation. • Cross ventilation induced by external wind direction changing. • Single-sided ventilation induced by flow separation. • Impact of window casements on turbulence-induced ventilation.