The Investigation and Modeling of the interaction between Paperboard Clippings in a Pipe Flow

Abstract: In the manufacturing process of Tetra Pak packages, holes are cut out of the paperboard for straws and caps. The left-over paperboard clippings, called confetti, need to be evacu- ated from the machine. However, this evacuation process has proven to cause problems due to jams arising as the confetti get stuck in joints and along the pipe walls. This study investigates how the confetti behave, deform and interact with each other, the flow and the pipe walls, to get a better understanding of how and why these jams occur. Fluid structure interaction (FSI), which is a class of multi-physics and deals with the inter- action between fluid flow and deformable structures, is employed to model the confetti in a pipe flow. An FSI-simulation model is developed, by using the software STAR-CCM+ and Abaqus/Standard, and is validated against experimental data. It is found that the confetti mainly lose kinetic energy, thus evacuation speed, when facing the flow with a small cross-sectional area or getting too close to the pipe wall, decelerating due to the near wall, low velocity flow. Colliding with other confetti or the wall does not affect the evacuation speed negatively. However, the initial position of the confetti influences its initial movement, thus the evacuation speed. A negative initial angle is found to be preferable compared to a positive inclination angle, since this decreases the risk for the confetti getting stuck in the near wall, low velocity flow. The FSI-simulations coincide well with the experiments, capturing the trajectory of the confetti through the pipe adequately. The simulation model over-predicts the evacuation speed, indicating that some of the losses arising in the experiments are not fully captured by the model. However, the model is considered to capture the course of events to a satisfying extent and can be used for future research and development at Tetra Pak.