Experimental Investigation of Air-Sand Two Phase Boundary Layer Flows over Obstacles.

Particle-laden turbulent flows are central to numerous industrial and environmental processes, yet the intricate interplay between dispersed particles and carrier fluids, particularly in the presence of geometric obstacles, remains insufficiently understood. This study presents a comprehensive experimental investigation into two-phase channel flows interacting with bluff body geometries, specifically triangular obstacles of varying size. Using Particle Image Velocimetry (PIV) in conjunction with a novel image processing method enabling air-particle phase separation, the work captures simultaneous measurements of airflow dynamics and sediment distribution within a controlled test channel. The analysis reveals how particle presence modulates turbulence characteristics, such as mean velocity, Reynolds shear stress, and wall-normal velocity. In particular, the results demonstrate that sediment accumulation and upward transport are significantly influenced by obstacle geometry, with larger obstacles generating stronger wake regions and enhancing upward particle flux. Comparisons between single-phase and two-phase flows highlight critical two-way coupling effects: sediment presence attenuates near-wall turbulence and flow acceleration, yet also entrains upward air motion along concentrated particle streams.