A CFD/DEM Approach to Determine the Flow Resistance of Randomly Packed Bed of Crushed Rock Particles

Abstract

Packed beds of crushed rock particles are typically encountered in the thermal energy storage system at a solar thermal power plant. Rocks have irregular shapes, and tend to pack with their long axes in a horizontal plane. As a results its resistance to airflow is anisotropic. Designing a bed for effective charging and discharging cycles, depends on an accurate prediction of the flow distribution through it. Ellipsoids are mathematically simple shapes that characterise crushed rock particles reasonably successfully. A packed bed was generated using a discrete element model, and the flow through the bed calculated with computational fluid dynamics. The resistance tensor for the bed was extracted from the data. The tensor is almost symmetrical, with the diagonal terms dominant. Incorporating this tensor as a source term in a porous medium presentation of a packed bed, should yield more accurate results than, say the Ergun equation, at very little extra computational overhead.

Microscopic investigation of the influence of complex stress states on internal erosion and its impacts on critical hydraulic gradients

“…Among these techniques, the coupled computational fluid dynamics and discrete element method (CFD‐DEM) has raised much attention because of its advantages in computational efficiency, especially compared with the Lattice Boltzman‐DEM coupling (LB‐DEM) 14 and pore‐scale finite volume‐DEM coupling (PFV‐DEM) 15 . Over the past few years, the CFD‐DEM method has been widely applied in erosion‐related problems 10,16–21 . Xiong et al 2 .…”

“…15 Over the past few years, the CFD-DEM method has been widely applied in erosion-related problems. 10,[16][17][18][19][20][21] Xiong et al 2 conducted simulations to study macroscopic, microscopic, and mechanical characteristics during suffusion. They found that the greater the angle between flow and gravity, the harder it was for internal erosion to occur and continue.…”

A DEM-CFD Approach for Predicting Pressure Drop Through Packed Bed of Crushed Rocks

“…The purpose of this work is to examine the effect of particle orientation on the flow characteristics and derive a pressure drop tensor across an anisotropic packed bed. As recommended by Hoffmann, the crushed rock was represented as an ellipsoidal to model the bed [12]. The ellipsoidal shape has the same volume and aspect ratio as the averages measured for roughly 100 rocks.…”

“…Particle size and shape have a significant effect on the pressure drop. For that reason, several particle shapes have been proposed to represent crushed rocks, including bricks, connected spheres, and ellipses [10] - [12]. The ellipsoidal shapes were more effective at presenting the crushed rocks than the other shapes [13].…”

“…The ellipsoidal shapes were more effective at presenting the crushed rocks than the other shapes [13]. Hoffmann [12] examined the sizes of crushed rock by randomly measuring more than 100 particles and determined that the average box sizes are 87.9 mm, 59.5 mm, and 37.4 mm.…”