Component-Resolved CFD-Based Assessment of Surface-Element Effects on Local Wind and Turbulence in a Coastal Harbor

Abstract Accurate quantitative assessment of near-surface wind and turbulence in coastal harbors remains challenging because terrain, vegetation, and built structures interact in a direction-dependent manner and are often treated using lumped or simplified surface representations in numerical models. This study presents a component-resolved Computational Fluid Dynamics (CFD)-based assessment of local wind and turbulence conditions over Mariehamn harbor in the Åland Islands. The objective is to quantify how individual and combined surface elements influence fairway-scale wind and turbulence exposure. Simulations were performed for eight wind directions using three surface configurations: terrain with buildings (TB), terrain with forests (TF), and terrain with both forests and buildings (TFB). The results show that forests dominate both wind-speed reduction and turbulence generation, with the TF and TFB configurations producing nearly similar flow patterns across most wind directions. A deviation-based analysis further quantified the relative influence of individual surface elements and showed that removing forests produces substantially larger changes than removing buildings, particularly in turbulence intensity at higher elevations. These findings highlight the dominant influence of porous vegetation on momentum loss and turbulence modulation in the lower atmospheric boundary-layer over complex coastal terrain. The resulting CFD dataset and component-resolved assessment approach provide a physically consistent basis for future integration into intelligent fairway and navigation-oriented decision-support frameworks.