Modeling and Simulation of two-phase flows

dc.contributor.advisor Shankar Subramaniam Garg, Rahul
dc.contributor.department Mechanical Engineering 2018-08-11T18:11:26.000 2020-06-30T02:30:03Z 2020-06-30T02:30:03Z Thu Jan 01 00:00:00 UTC 2009 2013-06-05 2009-01-01
dc.description.abstract <p>The primary objective of this study is to improve the predictive</p> <p>capabilities of two-phase flow simulations that solve for average</p> <p>equations, such as Lagrangian-Eulerian (LE) and Eulerian-Eulerian</p> <p>simulations. The predictive capabilities of LE and EE simulations</p> <p>depend both on the numerical accuracy and on the accuracy of models</p> <p>for the fluid--particle and particle-particle interaction terms. In</p> <p>the first part of this study, a high fidelity ‘true’ DNS approach</p> <p>based on immersed boundary method (IBM) is developed to propose</p> <p>accurate models for fluid--particle terms, such as interphase momentum</p> <p>transfer, and also interphase heat and mass transfer, by solving for</p> <p>steady flow and scalar transport past homogeneous assemblies of fixed</p> <p>particles. IBM is shown to be a robust tool for simulating gas--solids</p> <p>flow and does not suffer from the limitations of lattice Boltzmann</p> <p>method (LBM): (1) compressibility errors with increasing Reynolds</p> <p>number; (2) calibration of hydrodynamic radius; (3) non-trivial to</p> <p>extend to non-isothermal systems. In the Stokes regime, average</p> <p>Nusselt number from scalar IBM simulations is in reasonable agreement</p> <p>with the frequency response measurements of Gunn and Desouza (1974) and</p> <p>free surface model of Pfeffer and Happel (1964), but differs by as much as</p> <p>300 % from the widely used heat and mass transfer correlation</p> <p>of Gunn (1978), which is attributed to the unjustified assumption</p> <p>of negligible axial diffusion in Stokes flow regime made by Gunn. At</p> <p>higher Reynolds numbers, scalar IBM results are far from Gunn's</p> <p>correlations but in reasonable agreement with other experimental</p> <p>data. A correlation is proposed for heat and mass transfer as function</p> <p>of solid volume fraction and Reynolds for a particular value of</p> <p>Prandtl/Sherwood number equal to 0.7.</p> <p>In the second part of this study, the numerical accuracy of LE</p> <p>simulations is investigated because LE simulations are very frequently</p> <p>used to verify EE simulations, and as a benchmark in the development</p> <p>of new simulation techniques for two--phase flows, such as the recent</p> <p>quadrature method of moments QMOM (Fox, 2008). Accurate</p> <p>calculation of the interphase transfer terms in LE simulations is</p> <p>crucial for quantitatively reliable predictions. Through a series of</p> <p>static test problems that admit an analytical form for the interphase</p> <p>momentum transfer term, it is shown that accurate estimation of the</p> <p>mean interphase momentum transfer term using certain interpolation</p> <p>schemes requires very high numerical resolution in terms of the number</p> <p>of particles and number of multiple independent</p> <p>realizations. Traditional LE (TLE) simulations, that use real</p> <p>particles or computational particles having constant statistical</p> <p>weight, fail to yield numerically--converged solutions due to high</p> <p>statistical error in regions with few particles. We propose an</p> <p>improved LE simulation (ILE) method that remedies the above limitation</p> <p>of TLE simulations and ensures numerically converged LE simulations.</p>
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dc.identifier archive/
dc.identifier.articleid 1647
dc.identifier.contextkey 2806814
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/10657
dc.language.iso en
dc.source.bitstream archive/|||Fri Jan 14 18:25:30 UTC 2022
dc.subject.disciplines Mechanical Engineering
dc.subject.keywords direct numerical simulations
dc.subject.keywords fluidized and packed beds
dc.subject.keywords gas-solids flow
dc.subject.keywords heat transfer correlations
dc.subject.keywords Immersed boundary method (IBM)
dc.subject.keywords Multiphase flows
dc.title Modeling and Simulation of two-phase flows
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication 6d38ab0f-8cc2-4ad3-90b1-67a60c5a6f59 dissertation Doctor of Philosophy
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