Computational and experimental analysis of granular flow in hoppers

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Abstract
Hoppers are among the most widely used equipment for granular material processing in industry. We present experimental and DEM simulation results for the flow of granular material in wedge-shaped hoppers. The predictions of theory of Savage for a wedge-shaped hopper with frictionless walls and a theory using the μ–I rheology, are compared to DEM simulation results. The μ–I rheology gives a very good match to the simulation results. The velocity field in a quasi-2D wedge-shaped hopper, with front and back glass walls, is obtained experimentally using image analysis and particle tracking. We find that the radial velocity in cylindrical coordinates varies as v r ∝ θ 2 , and that the tangential velocity is non-zero, but much smaller than the radial velocity. The experimental velocity distributions closely match the DEM simulation results using calibrated parameters. DEM simulations without the front and back walls yield qualitatively similar results to the quasi- 2D case. Analysis of the flow in the exit region indicates that velocity varies smoothly over the domain and a free fall arch is not evident. The vertical acceleration data indicate that the particles experience free fall only a significant distance below the exit plane. The acceleration is larger than the acceleration due to gravity near the exit, which is explained in terms of an arch-buckling mechanism.

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