(134d) Development of a Drag Model for a Spherical Intruder in a Fluidized Bed

The penetration of large objects into granular materials is commonly encountered in both nature (e.g. impacts of meteors and projectiles) and engineering applications (e.g. insertion of tractor blades into sand). During the insertion and retraction period of the intruders, force chains continuously form and collapse leading to a resistive (i.e. drag) force on the intruder. The formation and structure of the force chains can be manipulated by introducing a fluid (e.g. air) into the granular material, leading to a reduction of the force acting on the intruder. In this work, a model for the drag force acting on a large (spherical) intruder penetrating into a fluidized bed is developed (for both the plunging and retraction period). In this work, computational fluid dynamics coupled  to a discrete element method is used to determine particle-particle and particle-fluid interactions. An important facet of this work was to study the effect of (i) the diameter ratio of the intruder to the fluidized bed particles, (ii) the intruder velocity and (iii) the fluidization state on the spatial distribution of the force chains in the granular bed.