Flow patterns and wall stresses in a moving granular filter bed with a curved symmetric louvered wall

This study investigated the flow patterns and wall stresses in a two-dimensional moving granular filter bed with a curved and symmetric louvered wall. A digital camcorder was used to record the flow pattern histories of the granular solids in the moving granular filter bed. The numerical predictions of the flow patterns were implemented using the discrete element method and compared with the experimental results. The variations in the dynamic wall stresses with time were obtained using a pressure gauge, which could simultaneously measure the normal and shear stresses of the granular solids. The effects of the curvature of the louvered wall and the exit width upon the flow patterns and the wall stresses were also elucidated. For a fixed value of radius of curvature, the ratio of the quasi-stagnant zone (Q-SZ) area in the third stage to the granular bed area in the third stage increases with decreasing width of the exit, but the average dynamic normal stress on the curved louvered wall increases with increasing width of the exit. For a fixed value of the exit width, both the ratio of the Q-SZ area in the third stage to the granular bed area in the third stage and the average dynamic normal stress on the curved louvered wall increase with increasing radius of curvature. Additionally, the curved louvered wall can not only shrink the area of the Q-SZ in the granular bed, but also reduce the dynamic normal stress on the louvered wall.