A Building Ensemble as an Aerodynamic System: CFD-Based Evaluation of Airflow Performance in the Context of Architectural Coherence

This study investigates the aerodynamic performance of a two-building ensemble as an integrated architectural–aerodynamic system, with a focus on airflow conditions relevant to building-integrated wind turbines. The research addresses the question of whether newly designed development can actively improve, rather than deteriorate, airflow conditions above existing buildings. A parametric CFD analysis based on steady-state RANS (SST k–ω) simulations was conducted for multiple geometric configurations of a reference building (A) and a neighboring building (B), varying roof pitch (22–40°) and height. Airflow was evaluated using mean longitudinal velocity (Vy), coefficient of variation (CV), and vector components across three architectural scenarios corresponding to different turbine-integration strategies. The results demonstrate that properly designed geometries can significantly enhance flow quality. In the near-roof scenario (Arch1), the optimal configuration achieved a 24.28% increase in Vy and a 94.53% reduction in CV, indicating strong flow stabilization. In the façade-integration scenario (Arch2), improvements reached +10.40% in Vy and −23.16% in CV, reflecting vertical homogenization of the flow field. In the point-based scenario (Arch3), a local velocity increase of 4.29% was obtained while maintaining directional stability. The findings indicate that building geometry acts as an active design parameter that controls flow intensity, homogeneity, and direction. The study proposes a CFD-based decision framework and demonstrates that architectural form can be deliberately shaped to enhance wind conditions, supporting the integration of wind turbines into coherent building design.