- Mechanical Engineering
Top 3 Areas of Expertise:
Expected date of graduation:
Fluidized beds are preferred for several applications in the energy, food and beverage, and pharmaceutical industries because of their superior heat and mass transfer characteristics. Fluidization hydrodynamics govern the bed performance, and modeling and simulation tools can provide insight into its underlying physics and aid the design and optimization of industrial systems. Modeling fluidization is a complex multiscale phenomenon, including particle contacting at the micro-scale and interaction and transport of meso-scale structures (bubbles/cluster) at the reactor scale. Further, there is considerable uncertainty in scaling-up due to lack of experimental data and limitations of existing computational capabilities. As such, there is a strong need for reliable and computationally efficient 3D simulations which can provide valuable insights into the hydrodynamics as well as the overall fluidized bed operation. Among different frameworks proposed for simulating fluidization, from 'resolved' discrete particle approaches to the Two-Fluid Model (TFM) in which the solid and gas phases are considered as interpenetrating continua, the latter is the only approach that lends itself viable to scaling to industrial scale reactors. This study aims at developing accurate and scalable computational tools to predict the gas phase (bubble) motion and solid phase (emulsion) circulation based on the TFM. These models, formulated using a combination of the kinetic and frictional theories of granular media, include constitutive relations and boundary conditions for the solids, as well as the particle-gas and particle-particle interactions terms, that must be modeled. Other challenges must be addressed, including the construction of grids that are fine enough to resolve bubbles (which drive solids motion) but without violating the solids continuum assumption, while conforming to the physical boundary of the bed. It is also critical to devise carefully constructed metrics which capture the fluidization hydrodynamics, in order to validate the results against available experimental measurements which will ensure reliability of predictions at large-scales. Further, coarse grid models must also be developed to reduce computational intensity without sacrificing accuracy. When completed, this will be among the first full-scale 3D CFD studies of fluidization, incorporating the necessary post-analysis tools, that address the needs of commercial scale fluidized beds, as well other applications of dense multiphase flow.
Top 5 Awards and honors (name of award, date received):
5 Recent Papers:
A. Bakshi, C. Altantzis, R.B. Bates, and A.F. Ghoniem (2016) "Study of the effect of reactor-scale on fluidization hydrodynamics using fine-grid CFD simulations based on the Two-Fluid Model" Powder Technology
A. Bakshi, C. Altantzis, R.B. Bates, and A.F. Ghoniem (2016) "Multiphase-flow Statistics using 3D Detection and Tracking Algorithm (MS3DATA): Methodology and Application to Large-Scale Fluidized Beds" Chemical Engineering Journal
A. Bakshi, R.B. Bates, C. Altantzis, and A.F. Ghoniem (2015) "Eulerian–Eulerian simulation of dense solid–gas cylindrical fluidized beds: Impact of wall boundary condition and drag model" Powder Technology
A. Bakshi, C. Altantzis, and A.F. Ghoniem (2014) "Towards Accurate Three-Dimensional Simulation of Dense Multi-Phase Flows Using Cylindrical Coordinates" Powder Technology
M.S. Hasnain, A. Bakshi, P.R. Selvaganapathy, and C.Y. Ching (2011) "On the Modeling and Simulation of Ion Drag Electrohydrodynamic Micropumps" Journal of Fluids Engineering.