Charles S. Campbell Charles S. Campbell
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Note that in the above pictures, the second and third plots are expanded to show the detailed flows around the bubble while the first and last plots show the entire bed and are plotted on the same scale. While a simulation of a two-dimensional fluidized bed experiment, (a bed that is narrow in the third dimension). This simulation is fully three-dimensional; the particles shown in the third plot are those that intersect a cut through the center of the bed.
The purpose of this project was to try and understand how particle pressures are generated in fluidized beds. The particle pressure is that portion of the total (gas+particle) pressure that is exerted only by the particle phase. Measurements of this data were made using a special probe in both 2-D and 3-D beds. The above plots were generated by a computer simulation of those experiments. The computer simulation employed a discrete element model (DEM) for the particle phase which was coupled through drag terms with a finite volume CFD model for the fluid phase. The simulated particle pressures agree quantitatively with the experimental values. The simulation code was written by a former postdoc of mine, Alexander Potapov. The code itself is the property of Dr. Potapov's current employer, Conveyor Dynamics Inc.
Publications relevant to the experimental portion can be found by clicking below:
Particle Pressure Publications
As of now, there are no publications regarding the simulation technique, although the above information has appeared as a poster at the 1999 annual meeting of the International Fine Particle Research Institute (IFPRI).
The above picture shows the velocities vectors from a computer simulation of a liquid particle shear flow (i.e the top wall is moving to the right while the bottom wall moves to the left creating a shear flow in the mixture between them). This technique employs a Discrete Element Model (DEM) to simulate the particle phase and Smoothed Particle Hydrodynamics (SPH) to model the motion of the interstitial fluid. The latter is a Lagrangian technique based on the Navier Stokes equations that treats the fluid as a series of moving interpolation points. It makes no assumptions about drag laws etc; the fluid particle interaction is solely through the application of the no-slip condition at the particle surface and by the pressure and viscous forces that act on the surface of the particles.
The goal of this project is to model the famous experiments by Bagnold (1954) that form the basis of modern granular flow theory and to try and resolve some ambiguities in those experiments. The simulation can quantitatively reproduce Bagnold's stress/strain-rate measurements. The simulation program was developed in collaboration with Melany Hunt of Caltech, and with Alexander Potapov currently with Conveyor Dynamics Inc.
For more information, you can read the text of a poster presentation of this work by clicking here: SPH Poster.
That poster was presented at the 1999 meeting of the International
Fine Particle Research Institute (IFPRI)
This page is created and maintained by Charlie Campbell.