标题： 筒仓排料过程中具有双角几何结构的表面凹陷 显示英文标题

标题： Surface depression with double-angle geometry during the discharge of close-packed grains from a silo

摘要： 当在标准填充条件下，粗颗粒从料仓中排出时，在表面形成一个具有单一坡度的锥形凹陷。 我们观察到，体积分数的增加会产生一个更复杂的凹陷，其特征是两个排料角度：一个较低的角度接近于标准填充时测得的角度，一个明显较大的上部角度。 坡度的变化出现在紧密填充的静止区域与中央流动通道之间的边界处，该流动通道形成于开口之上。 由于该区域的物料始终处于流化状态，流量不受床层初始填充的影响。 另一方面，当使用相同尺寸和密度的光滑颗粒时，这两个角度之间的差异明显较小，这表明高体积分数和摩擦力必须共同作用才能产生观察到的几何形状。 我们的结果表明，表面轮廓有助于通过简单的目视检查识别颗粒床的填充条件，这在工业中防止料仓排料过程中不希望发生的坍塌可能很有用。 显示英文摘要

摘要： When rough grains in standard packing conditions are discharged from a silo, a conical depression with a single slope is formed at the surface. We observed that the increase of the volume fraction generates a more complex depression characterized by two angles of discharge: a lower angle close to the one measured for standard packing and a considerably larger upper angle. The change in slope appears at the boundary between a densely packed stagnant region at the periphery and the central flowing channel formed over the aperture. Since the material in the latter zone is always fluidized, the flow rate is unaffected by the initial packing of the bed. On the other hand, the contrast between both angles is markedly smaller when smooth particles of the same size and density are used, which reveals that high volume fraction and friction must combine to produce the observed geometry. Our results show that the surface profile helps to identify by simple visual inspection the packing conditions of a granular bed, and this can be useful to prevent undesirable collapses during silo discharge in industry.