Use of GranuDrum Digital Twin to Evaluate the Relation Between the Cohesive Index and the Strength of Cohesive Interactions

  • Neveu, Aurélien (Granutools)
  • Lumay, Geoffroy (University of Liege)
  • Francqui, Filip (Granutools)

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Numerous processes involved fine powders with particles sizes below 100µm. However, when the size of the particles is reduced, the cohesion becomes the main driving mechanism conditioning the macroscopic behaviour. The notion of powder cohesion is not well defined, and the metrics associated to it are dependent to the characterization method employed. At the microscopic level, cohesion arises from a complex interplay between the cohesive interactions lying between the particles, mainly due to capillary forces and electrostatic charges. Therefore, having access to a measure of these interactions are usually out of reach. Discrete elements methods (DEM) are widely adopted nowadays to simulate particulate systems. However, the contact models employed are always a simplification of the contacts in a real material. Also, the determination of the contact parameters is a difficult task, in particular for fine cohesive powders. To overcome this difficulty, top-bottom calibration approaches have been developed, in which the model parameters are determined so that the simulated macro behaviour match the one of the real powder. The development of digital twins of well-established characterization methods help to facilitate this process [1]. In this study, we investigate the relation between the Cohesive Index, a measure of cohesion in a rotating drum method (GranuDrum, Granutools, Belgium), and the strength of the cohesive forces. The Cohesive Index evaluates the cohesion by means of the temporal fluctuations of the powder/air interface during the flow [2]. The coupling of a characterization in the real instrument with a DEM digital twin of the GranuDrum has been used to perform a relevant calibration of the model parameters. Then, DEM simulations have been performed at different Bond numbers, defining the strength of the cohesive interactions, and the resulting Cohesive Index for the simulated flow has been measured. A strong correlation between the microscopic cohesive forces and the macroscopic Cohesive Index metric is evidenced. [1] C.R.K. Windows-Yule and A. Neveu, “Calibration of DEM simulations for dynamic particulate systems”, Papers in Physics, 14, 140010 (2022). [2] A. Neveu, F. Francqui and G. Lumay, “Measuring powder flow properties in a rotating drum”, Measurement, 200, (2022).