Modeling the Dynamics of Fabric in a Rotating Horizontal Drum Using the Discrete Element Method

In order to provide a tool for designing more efficient methods of mixing fabric, a simplified discrete element computational model was developed for modeling fabric dynamics in a rotating horizontal drum. Because modeling the interactions between actual pieces of fabric is quite complex, a simplified model was developed where individual pieces of bundled fabric are represented by spherical particles. This model is essentially a ball mill. The simulations are used to investigate fabric bundle kinematics, the power required to drive the rotating drum, and the power dissipated through normal and tangential contacts. Parametric studies were performed to investigate the effects of fill percentage, baffles, rotation speed, friction coefficient, and coefficient of restitution. The simulation results indicate that fill percentage, drum rotation speed, and friction coefficient play significant roles in the fabric bundle dynamics. For example, the specific drum power increases by a factor of 600% to 800% as the fill percentage decreases from 75% to 25%. In addition, the maximum specific drum power occurs at a rotation speed just less than the speed at which centrifuging occurs. The friction coefficient does not play a significant role in the bundle dynamics for values greater than a critical value. The critical value decreases from a value of approximately 0.3 at a 25% fill percentage to 0.05 for a 75% fill percentage. For friction coefficients less than this critical value, the specific power decreases with decreasing friction coefficient. Drum baffles have a minor effect on the power dissipation and kinematics for fill percentages greater than 50%. Bundle size and coefficient of restitution have a relatively weak influence on the measured parameters.