Investigation of Transport Phenomena in the Presence of Interfaces: Forced Convection in Composite Porous/Fluid Domains, Solidification with a Mushy Region, and Meniscus Formation in Dip Coating Processing

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Title: Investigation of Transport Phenomena in the Presence of Interfaces: Forced Convection in Composite Porous/Fluid Domains, Solidification with a Mushy Region, and Meniscus Formation in Dip Coating Processing
Author: Xiong, Ming
Advisors: Andrey V. Kuznetsov, Co - Chair, Member
James C. Mulligan, Co - Chair, Member
William L. Roberts, Member
Robert E. White, Member
Abstract: Transport phenomena play an important role in many practical applications. Every time a new technology is developed, analysis of transport processes is crucial for its success. Numerical and analytical investigations of transport processes in forced convection in composite porous/fluid domains, solidification of binary alloys, and meniscus formation in dip coating process are performed. These processes include mass, momentum, and energy transport across interfaces. For forced convection in composite porous/fluid domains, the validity of single-domain approach is investigated via comparisons between the numerical and exact solutions. An analytical solution for fluid flow described by the Brinkman-Forchheimer-Darcy equation is obtained by utilizing the boundary layer approximation. Solidification of binary alloys is studied by utilizing a porous medium approach for modeling transport processes in the mushy zone. A three-phase model is developed to predict microporosity formation during this process. Solute redistribution during this process is modeled by using the Scheil and lever rules to describe solute transport at the local scale. The investigations show that initial hydrogen concentration is an important factor affecting microporosity formation. Also, some effective ways of controlling microporosity formation are suggested based on these investigations. Another process studied in this dissertation is the dip coating with liquid carbon dioxide used as a solvent. This is a new deposition technique developed in recent years. A model accounting for evaporation during this process is obtained based on the classical free meniscus theory. Numerical results agree well with experimental data. These results show that the dry film thickness increases with the increase of evaporation rate and initial solute concentration.
Date: 2001-10-26
Degree: PhD
Discipline: Mechanical Engineering
URI: http://www.lib.ncsu.edu/resolver/1840.16/4577


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