Rotating mesh framework and dynamic wind direction variability effects on building ventilation with large eddy simulation

Natural ventilation, a critical passive design strategy for indoor environmental regulation and urban pollution mitigation, relies heavily on dynamic wind patterns. However, existing studies predominantly focus on steady or averaged wind directions, often overlooking transient effects caused by time-varying wind direction fluctuations. This study addresses this gap by proposing a novel dynamic wind direction meshing framework integrated into large eddy simulation in computational fluid dynamics simulations to investigate how time-dependent wind direction variations influence natural ventilation efficiency and pollutant dispersion in isolated buildings. The model divides the computational domain into a steady zone and a dynamically rotating zone, enabling realistic wind direction variability while preserving computational efficiency. Validation against wind tunnel experiments confirmed high accuracy. Results indicate that even minor directional fluctuations (1° amplitude) reduce ventilation rates by 13.13% compared to steady wind conditions, whereas larger amplitudes (40°) exacerbate pollutant retention, with relative concentration errors exceeding 150%. Frequency variations (5–40 s periods) exhibited negligible impacts relative to amplitude-driven effects. Dynamic wind fields altered airflow by suppressing shear layer separation and forming transient low-pressure vortices, which disrupted pollutant diffusion pathways. A linear regression model quantified amplitude-dependent ventilation decay, offering predictive capabilities for dynamic wind scenarios. These findings highlight the necessity of incorporating short-term wind direction variability into urban airflow models to enhance building ventilation efficiency and pollutant dispersion. The proposed framework establishes a scalable methodology for ventilation design, providing physical insights to optimize airflow patterns and pollutant dispersion under time-dependent wind variability.