Lattice Boltzmann simulations of multiphase flows

This thesis is a comprehensive account of my experiences implementing the Lattice Boltzmann Method (LBM) for the purpose of simulating multiphase flows relevant to Air Conditioning and Refrigeration Center (ACRC) applications. Other methodologies have been used to simulate multiphase flow including finite volume based Navier-Stokes solvers. These methods have found reasonable success in simulating multiphase flows. LBM was chosen because of its ability to capture multi-fluid physics including phase-change and interfacial dynamics with relative ease. In addition, the LBM algorithm can be easily parallelized. This allows larger problems to be simulated quicker. Among the multiphase LBM algorithms, we have implemented the Shan-Chen method, the He-Chen method, and an extension to the He-Chen method. We carefully document our methodology and discuss relevant kinetic theory and fluid dynamics. We present results for a number of fundamental flow problems including droplet impingement on solid and liquid surfaces as well as multiphase flow in complex micro-channels. In addition, we examine in great detail the problem of axial droplet migration and deformation in a square-duct at moderate Reynolds number. Our results suggest that the LBM algorithm is capable of simulating a wide range of flows and can accurately capture flow physics provided the density ratio among fluid phases is not large. Because ACRC equipment often harbor high density ratio flows, the standard LBM procedures require modification to accommodate higher density ratio problems. We investigate one such modification to the He-Chen algorithm by introducing a pressure Poisson equation (PPE) to reduce density variation related to compressibility effects

Simulation of a reactive fluidized bed reactor using CFD/DEM

This report presents the numerical study of a semi-industrial fluidized bed, which involves a reactive fluid phase and an inert granular phase. The simulations are based on a meso-scale approach using the Discrete Element Method (DEM) to represent the Lagrangian phase behavior coupled with Large-Eddy Simulation (LES) for the fluid phase. To cope with the limiting ratio between mesh and particle size stemming from the CFD/DEM modeling, a dynamic thickened flame approach is used. This approach yields interesting results regarding the prediction of the bed critical temperature

The Interaction of αB-Crystallin with Mature α-Synuclein Amyloid Fibrils Inhibits Their Elongation

αB-Crystallin is a small heat-shock protein (sHsp) that is colocalized with α-synuclein (αSyn) in Lewy bodies—the pathological hallmarks of Parkinson's disease—and is an inhibitor of αSyn amyloid fibril formation in an ATP-independent manner in vitro. We have investigated the mechanism underlying the inhibitory action of sHsps, and here we establish, by means of a variety of biophysical techniques including immunogold labeling and nuclear magnetic resonance spectroscopy, that αB-crystallin interacts with αSyn, binding along the length of mature amyloid fibrils. By measurement of seeded fibril elongation kinetics, both in solution and on a surface using a quartz crystal microbalance, this binding is shown to strongly inhibit further growth of the fibrils. The binding is also demonstrated to shift the monomer-fibril equilibrium in favor of dissociation. We believe that this mechanism, by which a sHsp interacts with mature amyloid fibrils, could represent an additional and potentially generic means by which at least some chaperones protect against amyloid aggregation and limit the onset of misfolding diseases

A proposal for a coordinated effort for the determination of brainwide neuroanatomical connectivity in model organisms at a mesoscopic scale

In this era of complete genomes, our knowledge of neuroanatomical circuitry remains surprisingly sparse. Such knowledge is however critical both for basic and clinical research into brain function. Here we advocate for a concerted effort to fill this gap, through systematic, experimental mapping of neural circuits at a mesoscopic scale of resolution suitable for comprehensive, brain-wide coverage, using injections of tracers or viral vectors. We detail the scientific and medical rationale and briefly review existing knowledge and experimental techniques. We define a set of desiderata, including brain-wide coverage; validated and extensible experimental techniques suitable for standardization and automation; centralized, open access data repository; compatibility with existing resources, and tractability with current informatics technology. We discuss a hypothetical but tractable plan for mouse, additional efforts for the macaque, and technique development for human. We estimate that the mouse connectivity project could be completed within five years with a comparatively modest budget.Comment: 41 page