Utilizing periodic boundary conditions to save computational resources for assessing building natural ventilation in urban areas

Abstract

For the first time in literature, we innovatively conducted CFD simulations with periodic boundary conditions to predict coupled indoor-outdoor airflows for a full-scale 3D six-floor residential building unit in urban areas with uniformly building clusters. A few influencing parameters on building ventilation performance are comprehensively analyzed, including the impacts of the surrounding buildings, wind incident angle (θ), external opening designs, cross or single-sided ventilation modes, and indoor facilities. Ventilation evaluation is contingent on factors including air change rate per hour (ACH), the corresponding ACH of purging flow rate (ACHPFR), and age of air (τ).Results show that the efficiency of natural ventilation on each floor differs from previous research conclusions after considering the impacts of surrounding buildings. Single-sided ventilation is significantly less effective than cross-ventilation in all scenarios. Most cross-ventilation cases have one-order greater ACH and ACHPFR values compared to those with single-sided ventilation. The window-to-wall ratio on the windward and leeward sides can affect the natural ventilation rate of the corresponding rooms. A large leeward opening helps to increase the ventilation rate, especially for the rooms on the upper floor, but it decreases the ventilation for the rooms near the ground. Indoor furniture has an insignificant impact on outdoor airflow and natural ventilation efficiency.