Development of a virtual Couette rheometer for aerated granular material

Abstract

A novel rheometer to study the behavior of granular materials in an aerated bed of particles has been developed. The device, called the aerated bed virtual Couette rheometer, is shown to be able to measure the shear stresses in the quasi-static and in the intermediate flow regimes. To validate the instrument, a Newtonian fluid of known viscosity was first sheared. The device was then used for measuring the shear stress of nonaerated glass beads with three -3D printed cells of different sizes to validate the optimal radial position, r*, where both shear rate and shear stress are independent of the cell radius. The results for the nonaerated glass beads displayed Coulomb behavior. The same behavior was observed when the bed was aerated.These experiments also showed that for a fixed shear rate the shear stress decreases as the aeration velocity, U. increases. K E Y W O R D Saerated bed, rheology, glass beads, granular materials, inertial number

From Quasi-static to Intermediate Regimes in Shear Cell Devices: Theory and Characterisation

“…For a fixed fluidisation index, a good agreement was found between the results obtained with samples with the same angle of internal friction, μ, while the shear stress, τ, associated with a higher μ was systematically lower. Yahia et al (2020) demonstrated the potential of r* to standardise the measurements in Couette shear testers. The authors compared the use of three virtual cells of a varying radius and a fixed bed height ( Table 1).…”

“…10. It has been used in the study of granular material by several authors including Marchal et al (2009) and Yahia et al (2020). Both studies used the same strategy: the inner cylinder is replaced by an impeller with a longitudinal arrangement of equidistant straight baffles aligned with the radial direction, see Fig.…”

“…A more advanced design including aeration, called an Aerated Bed Virtual Couette Rheometer (AB-VCR) was proposed by (Yahia et al, 2020). The AB-VCR adapts a virtual Couette geometry similar to the one presented in Fig.…”

“…The inner cylindrical element (so-called virtual cell) has 3D printed six blades made of plastic material (ABS-M30i, SYS systems 3D Printing). Yahia et al (2020) conducted experiments with and without aeration.…”

Powder flow behavior governed by the surface properties of glass beads

“…In the literature, a vast body of researches conducted to study the powder flow behavior by different shear cell tests [48][49][50][51][52][53]. In our previous study we studied flowability of raw and hydrophobic glass beads with shear cell [31].…”