Professor Gabriel Tardos
City College of CUNY Chemical Engineering Department
"A Fluid Mechanistic Approach to Slow (Coulomb) and Intermediate Powder Flows"
ABSTRACT
Mass and momentum balance equations combined with special constitutive equations yield a set of general equations for powder flows that replace the equivalent (Navier-Stokes) equations of Fluid Mechanics. I describe in this talk, both theoretically and experimentally, the flow of a dry powder in two simple geometries: outflow from a plane (2D) hopper and shear flow in a cylindrical Couette device. The flow rate from the hopper and the dependence of the shear and overall torque on the rotating cylinder are predicted and measured. The important finding is that continuously sheared dry powders behave differently from powders started from rest and that solutions obtained for this case actually predict this behavior. Unfortunately, in the industrially important case, flow from a hopper, the theory over predicts the measured values by a factor of about four. A better agreement is obtained by assuming that the powder is compressible. Further improvement in the prediction results from a new averaging of the above equations proposed lately by S. Savage. I will describe the principle of the new theory and present some theoretical and experimental results obtained for the geometry of the Couette device.
BRIEF ACADEMIC/EMPLOYMENT HISTORY:
1977: Ph.D. (ME) - Israel Institute of Technology (Technion), Haifa, Israel
1978 – present: Assistant, Associate and Full (1987) Professor – CCNY
RECENT RESEARCH INTERESTS:
Powder Science and Technology; Granulation of powders; Powder Flows; Electrostatic effects in powders; Fluidization; Filtration of dusty gases.
Return to Fall, 2000 Seminar Schedule