Session Chair:
- Heinrich Jaeger, University of Chicago
Schedule:
| PRESENTATION | SPEAKER |
| Wet Granular Flows and Structures | Arshad Kudrolli, Clark University |
| Electrostatic Charging During Granular Flow | Daniel Lacks, Case Western Reserve University |
| Particles Interactions Resulting in Electrostatic Charge Generation in Gas-Solid Fluidized Beds | Poupak Mehrani, University of Ottawa |
Wet Granular Flows and Structures
Arshad Kudrolli, Clark University
We will examine the properties of wet granular matter where the interplay of capillary and viscous forces and inertia can be important to their observed properties. We will first review work on our understanding of the impact of cohesive partially wetting liquid on the stability and flow properties of wet granular matter and particle segregation. Then, we will examine how these properties can be exploited to self-assemble a wide variety of intricately designed slender pillar and arch structures by simply pouring a granular suspension onto a liquid absorbing surface. We will discuss its potential for rapid manufacturing techniques such as 3D printing. Then, we will examine the interaction of liquid flow with sedimented granular beds leading to onset of motion and development of heterogeneity. Implications to boreholes and other geotechnical problems will be discussed.
Electrostatic Charging During Granular Flow
Daniel Lacks, Case Western Reserve University
Contact charging occurs when two materials are brought into contact and then are separated – as a result of the contact, charge is transferred such that one material becomes charged positively and the other becomes charged negatively. Everyone is familiar with this effect, even children who have ‘experimented’ by rubbing a balloon on their hair and seeing the balloon and hair become highly charged. But which material charges positively and which charges negatively? The answer to this simple question is not really known. In contrast to the tremendous progress in most fields of science, the understanding of contact charging is not much better now than it was 2500 years ago. In our research, we use a combined experimental-theoretical approach to study the factors affecting contact charging, with a focus on the charging that occurs as granular materials flow. We show that the particle size distribution can in some cases direct charge transfer, such that smaller and larger particles tend to charge to opposite polarities. We also show that material stress can play a dominant role in the charging process, and in some cases reverse the direction of charge transfer.
Particles Interactions Resulting in Electrostatic Charge Generation in Gas-Solid Fluidized Beds
Poupak Mehrani, University of Ottawa
In any gas-solid processing system, generation of electrostatic charges is inevitable due to particles interactions (i.e., continuous contacts between particles, and the particles and the containing vessel). Electrostatic charging could in turn result in problems of inter-particle cohesion or vessel wall adhesion. The extent of the net exchange of electrostatic charge between any surfaces depends on various parameters including the materials electrical properties, surface chemistry, environmental conditions and many more. This talk will focus on electrostatic charge generation in gas-solid fluidized beds and issues of particle agglomeration and reactor fouling in some commercial operations, and presents common measurement techniques applied for fluidizing particles electrostatic charge characterization as well as a brief summary of parameters that could affect the degree of particles charging.