(6dn) Bridging the Scales: From Contact Mechanics to Fluidized Beds

Flows of dry or wet particulate materials are prevalent in the chemical and pharmaceutical industries, in processes such as slurry transport, spray coating, coagulation, filtration, drying, granulation, agglomeration, and pneumatic transport. Such flows can also be observed in natural phenomena as varied as sedimentation, coastal erosion, debris flows, pollen capture, and planetary ring dynamics.  Particulate flows are expected to be prevalent in future space applications, including solids processing on flights, mining of lunar and Martian soils, powdered food and drink handling, etc.  Despite their pervasiveness in both industry and nature, particle processes remain poorly understood and yet their understanding is essential in order to tackle the energy challenges of the next few decades, be it with particle-catalyzed fuel cells, clean coal combustors, or coal gasification technologies, to mention a few.

I am presently a Research Associate in Chemical Engineering at the University of Colorado at Boulder, having completed my graduate studies in Mechanical Engineering at the California Institute of Technology in May 2003. My areas of interest include particle technology and multiphase flows in general, thermodynamics, and heat transfer, with a particular interest in rheology, friction, and contact models.

To date, prediction of complex phenomena such as multi-particle drag, species segregation, mixing, entrainment, elutriation, and attrition, to name a few, has essentially been limited to empirical correlation.  A physically-based overhaul of the existing predictive models in particle technology is urgently required.  My background and experience make me especially well suited for performing research in this area, with respect to both the experimental aspects (how to design, test and analyze systems that identify and quantify the relevant physics in particulate flows) and the multi-phase flow and contact mechanics theory aspects (the creation and validation of models required to treat such systems analytically and in numerical simulations).

I was first exposed to particle technology as an undergraduate researcher at the National University of Mexico. Under the mentorship of Professor Baltasar Mena I modified a version of a DEM code developed at the Lawrence Livermore National Laboratory and used it to simulate various granular flows. My Ph.D. research under the mentorship of Professor Melany L. Hunt at Caltech focused on determining the effect of a viscous fluid on the rebound of a macroscopic particle impacting a flat wall, both in oblique and normal settings. At Colorado, as a Research Associate sponsored by Professor Christine M. Hrenya, I have designed and built a fluidized bed system for studying elutriation and species segregation. The project started as a collaboration through the NSF Grant Opportunities for Academic Liaison with Industry (GOALI) program. A follow-on GOALI project, for which I am a co-principal investigator, was awarded earlier this year.

At both Caltech and Colorado, I have worked closely with undergraduate students. In addition to serving as a teaching assistant, I have directly mentored 10 students in research projects that led to several peer-reviewed publications and conference presentations. This summer, I had the opportunity to teach Fluid Mechanics at the University of Colorado during the June 2007 summer semester, a course that I am teaching again during the present fall semester. In addition, I am presently teaching one of the sections of the First Year Engineering Projects, a nationally-recognized course that gives students the opportunity to put engineering theory into practice early in their undergraduate years through working in teams to design, build and test new products and inventions. Based on my experience in experimental collaborative work and in one-on-one student mentoring, I believe that I have the necessary leadership and teaching skills to direct a diverse group of collaborators and students.

As a faculty member I intend to create a research group that bridges the gap between microscopic (particle-level) physics and predictions at the macroscopic level. The group will grow based on the following initial directions, which I consider crucial for a physical understanding of particulate flows: 1) analysis of the contact interactions in multiphase particulate systems, 2) characterization of the effects of surrounding fluids on the flow of these materials, and 3) development of novel instrumentation necessary for critical validation of theoretical models.

Publication Record

1.   Leboreiro J, Joseph GG, Hrenya CM (2007) Revisiting the standard drag law for bubbling, gas-fluidized beds, Powder Technology, invited paper (in press).

2.   Leboreiro J, Joseph GG, Hrenya CM, Snider DM, Banerjee SS, Galvin JE (2007) The influence of binary drag laws on simulations of species segregation in gas-fluidized beds, Powder Technology, in press.

3.   Joseph GG, Leboreiro J, Hrenya CM, Stevens AR (2007) Experimental segregation profiles in bubbling gas-fluidized beds, AIChE Journal, in press.

4.   Muite BK, Hunt ML, Joseph GG (2004) The effects of a counter-current interstitial flow on a discharging hourglass, Physics of Fluids, 16(9), 3415–3425.

5.   Joseph GG and Hunt ML (2004) Oblique particle–wall collisions in a liquid, Journal of Fluid Mechanics, 510, 71–93.

6.   Joseph GG and Hunt ML (2002) Wall erosion due to normal particle–wall collisions in a liquid, Proceedings Fourth World Congress on Particle Technology, Sydney (New South Wales, Australia).

7.   Jaimes J, Joseph GG, Geffroy E, Mena B, Herrera–Velarde JR (2002) Pattern formation in oscillatory granular flows, Revista Mexicana de Física, 48(6), 534–538.

8.   Joseph GG, Zenit R, Hunt ML, Rosenwinkel AM (2001) Particle–wall collisions in a viscous fluid, Journal of Fluid Mechanics, 433, 329–346.

9.   Joseph GG, Geffroy E, Mena B, Walton OR, Huilgol RR (2000) Simulation of filling and emptying in a hexagonal-shape solar grain silo, Particulate Science and Technology 18(4), 309–327.

10.  Zenit R, Joseph GG, Hunt ML (1999) The coefficient of restitution for liquid immersed collisions, Proceedings 3rd ASME / JSME Joint Fluids Engineering Conference, San Francisco (California, USA).

11.  Joseph G, Geffroy E, Mena B (1999) Flow of granular materials in a hexagonal silo, Revista Mexicana de Física, 45(Suppl. 1), 128–133.

12.  Joseph G, Mena B, Moreno E, Sansores E, Walton OR (1996) Granular Flow in a Solar Hexagonal Silo, Proceedings XIIth International Congress on Rheology, Aït-Kadi A, Dealy JM, James DF, Williams MC, editors, Québec (Québec, Canada), 795–796.