COhesive Powders: INnovative Tools – COPRINT

Experimental methods and numerical simulations

Design and qualification of a controlled-cohesion granular material, unsensitive to humidity. Development of a cohesive DEM code. Indentification of relevant dimensionless numbers.

Various experimental tests on flows and rheology. Calibration of in-house numerical codes.

Paper submitted

Granular matter and powders are widely used in the manufacturing of numerous products and in many industries. Despite this intense utilisation, their behaviour and rheological properties are still badly understood. 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. A concept of “flowability” has been introduced through different qualitative indexes to characterize the ability of powder to flow, but the flowability is not clearly related to physical and rheological properties of the powder. As a result, characterization tools available for the companies working with powders provide disparate measurements and only give qualitative information about the flow properties. Our objectives in this COPRINT proposal is twofold: 1) providing a physical understanding of the concept of flowability by studying the rheology of powders in various configurations both experimentally and numerically. 2) designing innovative tools to characterize powders for the industrial partner.
The first goal will be achieved by coupling experiments on a controlled-cohesive granular material as well as on real industrial powders with numerical simulations both discrete and based on continuum modelling. In the same spirit as what has been developed the last 15 years to study dry granular materials, our study will focus on simple but physically relevant configurations like inclined planes, shear cells, rotating drums. A central question we would like to focus on, will be the response of the powder to transient flows and to perturbations, to test if the flowability concept might be related to clogging instability. The second aim of the project is to use our better knowledge of the rheology to design new tools to characterize powders in industrial environments. The design of these new tools should be simple enough to be implemented in severe industrial conditions but should also provide quantitative measurements directed related to the rheological properties of the material. Three configurations have been identified as potentially relevant: inclined plane, flow around a cylinder and rotating drums.
This ambitious project of both academic and industrial interest is proposed by a consortium of 3 partners, two complementary academic laboratories (IUSTI and ?’Alembert) and an industrial partner (CREE Saint Gobain) and will take place on a long-term program of 4-years. It will gather scientific, academic and industrial skills and should extend the recent progresses on the rheology of granular matter to cohesive powders and provide new tools for an industrial usage.