Abstract: Wind induced noise occurs when airflow passes through narrow architectural openings such as window interface gaps, louvres, vents, façade joints, or around elements including fins, balustrades, or decorative cladding. These interactions can generate tonal or broadband noise often perceived as whistling, humming, or howling, particularly under elevated wind conditions. This study examines the potential for wind induced noise generated by architectural façade features and make up air ducts provided for pressure balancing when exhaust fans operate with all other windows closed in a 29 storey mixed use tower in Sydney. Computational Fluid Dynamics (CFD) simulations were undertaken to characterise airflow behaviour through these restricted pathways. The CFD framework predicts turbulence kinetic energy, dissipation rates, and aeroacoustic power transmitted through the gaps and around façade appurtenances. A detailed three-dimensional model of the development was constructed from architectural drawings, incorporating façade features, site topography, surrounding buildings, exhaust fans, natural ventilation plenums, and associated ductwork. The assessment required the simultaneous resolution of micro-scale airflow phenomena within millimetre-scale openings and macro-scale wind interactions across the surrounding urban environment, presenting significant numerical and modelling challenges. Simulations were performed using directional wind speeds corresponding to the 1-year return-period wind climate. A mesh sensitivity assessment informed the adoption of a refined polyhedral mesh comprising 85,868,224 nodes to resolve complex flow structures around the openings. Multiple window-opening scenarios were evaluated, including a critical operational condition in which all windows remain closed and fresh air is supplied exclusively through a natural-ventilation make-up air duct incorporating a motorised damper with a small clearance gap. This scenario is particularly relevant for apartments exposed to elevated external noise levels where façade openings may remain closed for extended periods. The results demonstrate the effectiveness of CFD as a design tool for identifying and mitigating wind-induced noise risks, providing practical guidance for optimising façade and ventilation-system design during the early stages of project development. Such assessments remain relatively uncommon in the published literature due to the challenges associated with integrating CFD modelling, wind-engineering statistics, mechanical ventilation requirements, architectural constraints, and aeroacoustic analysis within a unified workflow. The study also discusses the numerical challenges associated with simulating coupled internal and external flows across multiple length scales, including mesh-generation requirements, solution stability, and the accurate resolution of local flow structures governing aeroacoustic source mechanisms.

Keywords: CFD, Wind-Induced Noise, Complex Built Environment, Apartments on Noisy Road, Coupled External and Internal Flow Assessment, Turbulence Dissipation, Acoustic Power, Make-up Air Ducts

Pages: 99-112