Engineering Commons^™

Modeling Dewetting, Demixing, And Thermal Effects In Nanoscale Metal Films, Ryan Howard Allaire

Dissertations

Thin film dynamics, particularly on the nanoscale, is a topic of extensive interest. The process by which thin liquids evolve is far from trivial and can lead to dewetting and drop formation. Understanding this process involves not only resolving the fluid mechanical aspects of the problem, but also requires the coupling of other physical processes, including liquid-solid interactions, thermal transport, and dependence of material parameters on temperature and material composition. The focus of this dissertation is on the mathematical modeling and simulation of nanoscale liquid metal films, which are deposited on thermally conductive substrates, liquefied by laser heating, and subsequently …

Electric Field Induced Self-Assembly Of Mesoscale Structured Materials And Smart Fluids, Suchandra Das

Dissertations

This dissertation aims to study the forces that drive self-assembly in binary mixtures of particles suspended in liquids and on fluid-liquid interfaces when they are subjected to a uniform electric or magnetic field. Three fluid-particle systems are investigated experimentally and theoretically : (i) Suspensions of dielectric particles in dielectric liquids; (ii) Suspensions of ferromagnetic and diamagnetic particles in ferrofluids; and (iii) Dielectric particles on dielectric fluid-liquid interfaces. The results of these studies are then used to estimate the parameter values needed to assemble materials with desired mesoscale microstructures.

The first fluid-particle system studied is an electrorheological (ER) fluid formed using …

Studies Of Two-Phase Flow With Soluble Surfactant, Ryan Peter Atwater

Dissertations

Numerical methods are developed for accurate solution of two-phase flow in the zero Reynolds number limit of Stokes flow, when surfactant is present on a drop interface and in its bulk phase interior. The methods are designed to achieve high accuracy when the bulk Péclet number is large, or equivalently when the bulk phase surfactant has small diffusivity

In the limit of infinite bulk Péclet number the advection-diffusion equation that governs evolution of surfactant concentration in the bulk is singularly perturbed, indicating a separation of spatial scales. A hybrid numerical method based on a leading order asymptotic reduction in this …

Distribution Of Velocities And Velocity Gradients In Mixing And Flocculation Vessels : Comparison Between Ldv Data And Cfd Predictions, Changgen Luo

Dissertations

Flocculation is an operation of significant industrial relevance commonly encountered in many processes, including water and wastewater treatment. The physico-chemical phenomena of this process is strongly affected by the magnitude of the velocity gradients generated, typically through agitation, in rapid mix devices and flocculation vessels.

In this work the fluid dynamic characteristics of mechanically agitated systems, namely three different types of stirred tanks, which can be used as flocculation vessels, were studied. Both the mean and fluctuating velocities in all three directions were measured by using a Laser-Doppler Velocimeter (LDV). The velocity distribution, fluctuating velocities, power consumption and local velocity …

Vapor-Liquid Phase Equilibria Of Nonideal Fluids With A Ge-Eos Model, Socrates Ioannidis

Dissertations

This study dealt with the prediction and correlation of vapor-liquid equilibria behavior of nonideal fluids. The thermodynamic formalism of the G^E-EoS models, which combines the two traditional methods γ-Φ and Φ-Φ used so far for low and high pressure phase equilibria correlations respectively, has been combined with the 1FG^E model, based on one-fluid theory, to produce a more consistent approach to the phase equilibrium problem.

In the first part of our study we examine the predictive abilities of our model for vapor-liquid equilibria of highly nonideal fluids. The results establish the fact that the Huron-Vidal mixing rule …

Agitation Requirements For Complete Liquid Dispersion In Liquid-Liquid-Gas Systems, Emad Ahmad Abu-Hakmeh

Theses

A number of studies have been published in the literature on the determination of the agitation intensity at which two immiscible liquids become completely dispersed in mechanically agitated vessels. However, no information is currently available on the agitation intensity required for the complete dispersion of two liquids in the presence of an additional gas phase. Therefore, the main objective of this study was to experimentally determine the minimum agitation speed for complete liquid-liquid dispersion, N_cd, in liquid-liquid-gas systems as a function of gas flow rate, impeller type, impeller size, and impeller off-bottom clearance. The minimum agitation speed was …

Agitation Requirements For Complete Drawdown Of Floating Solids In Stirred Tanks, Joseph Philemon Mmbaga

Theses

The agitation requirements for complete drawdown of floating solids in mechanically agitated tank vessels has been studied both theoretically and experimentally.

A semi-theoretical equation has been derived on the basis of Kolmogoroff's theory of isotropic turbulence to determine the minimum impeller speed required for drawdown. The equation contains one adjustable parameter which has been found to be a function of the impeller type and position in the tank vessel.

The equation was tested using various vessels and impeller configurations. The solid phase consisted of high density polyethylene (density = 897kg/m³), low density polyethylene (density = 840kg/m³) …

Stability Of Bicomponet Polymeric Liquids In Poiseuille Flow, Chin-Chang Jeng

Theses

Polymer processing, involving two or more components, has become more popular recently in industrial plants. However, product Quality is affected very much by the fluid stability. Some theoretical and experimental results concerning Newtonian and non-Newtonian flow in rectangular coordinates, have been published, and the fluid-fluid interfaces were observed to be unstable by some researchers.

In this paper, the linear stability of bicomponent non-Newtonian fluids flowing in a cylindrical tube was investigated by using the Ellis model. Only the very long wave and the axisymmetric disturbances were considered. The Ellis zero-shear-rate viscosity ratio, m( = η02 / η01 )destabilizing. The half-zero-shear-rate-viscosity …

The Slow Settling Of A Sphere In A Viscous Fluid In The Proximity Of A Corner, Joseph Kisutcza

Theses

Experimental settling velocities for three different sizes of Delrin spheres in Ucon lubricant were determined at 20.2 degrees Celsius in order to confirm the validity of a theoretically derived equation for the settling of a sphere in the proximity of a corner. The experiments were conducted in a wedge shaped column with a circular sector base, filled with the viscous fluid, where the angle of the wedge was varied for experimental purposes. The distance from the wedge apex to the particle was also changed for the different runs.

The experimental data gave a good approximation of the values evaluated by …

The Settling Of Particles In A Square Contained Medium, Richard S. Matyas

Theses

Stokes' Law, has been standardly utilized to calculate the terminal velocity of falling particles. However, the limitation of Stokes' Law is that it does not take into account the container walls and their resulting drag forces. Extensive work with additional drag due to cylindrical container walls has been examined by many investigators. The classical and earliest is the well know Ladenburg Correction which cannot be utilized with non-cylindrical containers. This experimental thesis examines the analog of the Ladenburg relationship for a square container. This experimental thesis was undertaken to experimentally determine the value of the constant K₁ for a …

A Study Of Fluid Flow Entering A Sharp-Edged Channel, Rocco Racano

Theses

Experimental investigations were carried out on an newtonian fluid In the two dimensional case through the regions of a sharp-edged entrance and exit. Qualitative and quantitative results were compared to a variation of a two dimensional case of converging flow in a capillary as originally derived by Oka and proposed by Philippoff. In addition velocity profiles were taken in the entrance region. Furthermore, the effect of temperature gradients in the slit region with their resulting optical effects were considered. The methods used to obtain these goals were photoelasticity and streak photography.

Results were four, to be consistent with the theory …