Agglomeration and de-agglomeration of rotating wet doublets

Abstract

In this work, experiments using a pendulum apparatus were conducted for two particles engaged in oblique, wetted collisions over a range of impact angles, impact velocities, coating thicknesses, liquid viscosities, particle materials, and particle radii. From previous studies on normal or head-on collisions, the two particles bounce apart if the Stokes number (a ratio of particle inertia to viscous forces) exceeds a critical value, whereas they stick together if the Stokes number is below this critical value. However, for oblique collisions, an additional outcome is observed at moderate Stokes numbers and impact angles, in which the spheres initially stick together, rotate as a doublet, and then separate due to centrifugal forces. We refer to this outcome as 'stick-rotate-separate'. For subcritical Stokes numbers exhibiting this new outcome, the experimental results for the apparent coefficient of normal restitution and angle of rotation from impact to separation show only weak dependence on the fluid viscosity and thickness and the dry restitution coefficient, whereas they both decrease with increasing particle radius. These results are in contrast with those for supercritical Stokes numbers in which the spheres bounce upon impact. An accompanying theory based on lubrication forces, the glass transition of the liquid layer, and solid deformation and rebound agrees well with experimental results and gives insight into the observed trends.

Stokes’s Cradle: Newton’s Cradle with Liquid Coating

“…The outcomes as velocity is increased are FA, RNC, and FS, and do not include the NC outcome, which is counter-intuitive given our experience with the toy. In our companion work [15], we presented a new, firstprinciples model that is able to predict the correct progression of outcomes shown in Fig. 2, including the absence of NC, which is consistent over the large parameter space examined in that work.…”

“…Additionally, air resistance is neglected, as is gravity except to provide the initial velocity of the striker sphere (the long pendulum lines are restricted to small departures from vertical during the collision). The relevant equations of motion for two wetted spheres are provided in our previous work [15] and contain no fitting parameters. As the spheres approach each other, they (i) experience resistance starting at the separation x 0 during approach due to lubrication, (ii) may reach a minimum separation and reverse direction due to one of three criteria, and (iii) experience resistance upon rebound until the separation reaches x f , noting that there is not sufficient fluid from the initial layer (1-2 pair) or bridge (2-3 pair) to fill larger gaps.…”

“…2, as well as other observed experimental trends. Further details are given elsewhere [15]. Encouraged by the correct model prediction of the experimental trends over a wide parameter space, we have extended the parameter space of the model even further to explore the possibility of achieving the NC outcome.…”

Estimation of the dominant size enlargement mechanism in spray fluidized bed processes

“…The system of differential equations is solved numerically using the solver ode15s provided by MATLAB. The partial differential equations given in Equations (21), (22), and (43), are discretized using a finite volume scheme. Additionally, in the case of Equation (43), a flux-limiter function given by Koren 46 is used to reduce numerical diffusion.…”

Effects of aggregation on the kinetic properties of particles in fluidised bed granulation

“…This means that any relative collision energy between the colliding particles less than that would succeed for aggregation [53]. It is worth mentioning that this energy can be explored to include the rotation [84,85] of the aggregating particles. However, the calculation of θ* is not the scope of this article so will not be sought.…”