Investigation of sand surface deformation around simplified obstacles: Wind tunnel experiment with high-resolution photogrammetry and CFD

A wind tunnel experiment is conducted to examine the deformation of the sand surface around surface-mounted obstacles with a simple shape. The undulations of the sand surface are quantitatively measured with high resolution using a photogrammetric method. Shape-specific sand deformation characterized by significant erosion and slight deposition is observed in the vicinity of the obstacles, consistent with previous studies. Based on the measurement results, the effects of obstacle shape and size and wind direction on the deformation of the surrounding sand are investigated in detail. Since the changes in the sand surface deformation around obstacles are caused by the interaction between the wind flow and sand particle movement, information on the flow field around an obstacle is important for understanding the associated phenomena. However, it is extremely difficult to measure the wind velocity distribution in detail, in particular the wind shear velocity. Therefore, this study uses the detailed wind shear velocity around obstacles predicted by a validated computational fluid dynamics (CFD) simulation without considering sand particle movement. Pointwise indicators such as wind shear velocity and the divergence of shear velocities simulated by CFD are compared with the measured sand depth distributions and their suitability as indicators for sand deformation is discussed. The findings can be used for model development and the validation of CFD simulations that incorporate sand surface deformation.