Cohesive Granular Materials, Description and Flowing Properties

May 27, 2019 — May 31, 2019


  • Blanche Dalloz (Aix-Marseille University, France)
  • Maxime Nicolas (Aix-Marseille University, France)
  • Pierre Jop (CNRS-Saint-Gobain, Aubervilliers, France)

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Granular matter and powders are widely used in the manufacturing of numerous products and in many industries. Despite this intense utilization, their behavior and rheological properties are non-trivial. One major difficulty is that powders and their ability to flow are strongly affected by cohesive effects. In worst cases, the flow may stop and is somehow difficult to start again. The main objective of this course is to provide an overview of the knowledges on cohesive powders from the academic and industrial point of view. The course will cover three different scales.

At the particle scale, the particle motion is mainly governed by friction, particle-to-particle cohesion, interaction with walls. The physical origins of the cohesion (Van der Waals, electrostatic or magnetic forces, capillary forces, chemical forces, polymer layers) will be presented in detail. Two courses will be devoted to this topic. The effects of the cohesion driven by humidity on powders will be discussed in detail in one course, both from an experimental and numerical point of views. Physico-chemical aspects and adhesion mediated by soft media will also be covered by a specific series of lectures.

At a larger scale, where many particles interact, discrete or continuous models may be depicted. A numerical technique such as the DEM may be very useful to have a close insight on coarse-grained particle volume fraction, velocity, forces and stresses in a lab-scale volume containing cohesive particles. On the other hand, experiments with rheometers, inclined planes, rotating drums, hoppers, piles can provide useful elements to build an elementary continuous model. Three series of lectures will develop the techniques to prepare a cohesive granular material and the principal ways to study the static properties and the flow behavior of cohesive material.

At last, at an even larger scale, the course will present issues and solutions occurring in large volume systems such as silos, hoppers, transporting ducts, and other industrial equipment dealing with a large quantity of material. A series of lectures will focus on handling operations and will discuss how the powder rheology may bring useful facts about the industrial processes.

One of the key feature of this course is to propose to attendees a wide scope on the subject, from contact interaction theory to commercially available apparatus (powder rheometers).

The lectures are mainly designed for doctoral students of applied physics, mechanics, engineering and chemical engineering with a strong research interest in theoretical modeling, numerical simulation and experimental. They are also suited for young and senior researchers working in academia or in private research and development centers, interested in gaining a compact yet comprehensive overview of cohesive powders from its fundamental physical background, to the computational methods and the experimental techniques available for measuring the flow properties of such powders.


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