Coupled simulation of airflow and sand surface evolution around a bluff body: Dynamic-mesh CFD analysis with wind tunnel validation

Aeolian sand transport, which involves both erosion and deposition, plays a critical role in the built environment of coastal and desert regions. This study investigates the capability of a dynamic-mesh approach within computational fluid dynamics (CFD) to improve predictions of sand surface evolution around a bluff body. Wind tunnel experiments are conducted under atmospheric boundary layer conditions, where erosion and deposition patterns are quantified using a photogrammetric method. The proposed CFD framework, which explicitly updates the sand surface during the simulation, is systematically compared with a conventional static approach, in which the flow field is solved over a fixed surface. Grid sensitivity is assessed and the influence of an empirical erosion coefficient is examined. The results demonstrate that the dynamic-mesh approach generally shows better agreement with experimental observations, reproducing wider erosion zones and smoother surface transitions. In contrast, the static approach tends to produce overly localized and steep erosion profiles. Although some discrepancies remain, particularly in the windward region where erosion in front of the obstacle is not well reproduced, the dynamic approach better represents the interaction between sand surface evolution and the near-surface shear stress distribution. These findings highlight the importance of morphodynamic feedback in aeolian transport simulations and demonstrate that dynamic-mesh CFD offers a promising framework for predicting erosion–deposition processes, with potential applications in the design of sand mitigation measures.