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Articles 1 - 10 of 10
Full-Text Articles in Engineering
Shear Thickening In Dense Bidisperse Suspensions By Dynamic Simulation, Nelya Malbranche
Shear Thickening In Dense Bidisperse Suspensions By Dynamic Simulation, Nelya Malbranche
Dissertations and Theses
Shear thickening, which corresponds to an increase of viscosity with shear rate, is ubiquitously observed in many concentrated suspensions and, as such, has implications for many industrial materials and geological phenomena. Controlling shear thickening is of significant importance, and many studies have been devoted to it. Recent works link shear thickening to the shear-induced transition from a lubricated particle interaction at low shear stress to a predominantly frictional interaction at high stress. In this dissertation, we investigate bidispersity and focus on mechanisms contributing to the viscosity evolution in rate-dependent suspensions, something that has not been addressed before. We perform detailed …
Fundamentals Of Microgel Flooding And Nanoparticles-Stabilized Foams In Enhanced Oil Recovery, Shuaijun Li
Fundamentals Of Microgel Flooding And Nanoparticles-Stabilized Foams In Enhanced Oil Recovery, Shuaijun Li
Dissertations and Theses
For centuries oil has remained a critical energy source for human civilization. After years of extraction, many oil fields have reached or are reaching a decline stage of production, even though up to a half of the total crude oil reserves in these fields has not been recovered yet. One reason is due to the structural heterogeneity of the oil reservoirs—reservoirs may consist of regions of higher permeability with larger pore size and regions of lower permeability with smaller pore size. Displacing fluids tend to flow through large permeability zones only without reaching the oil trapped in low permeability region; …
Droplets In An Electric Field: Surface Rheology, Coalescence And Rebound, Yu Han
Droplets In An Electric Field: Surface Rheology, Coalescence And Rebound, Yu Han
Dissertations and Theses
Electrocoalescence is the process in which pairs of conducting droplets suspended in a continuous dielectric (nonconducting) liquid phase are drawn together and merge upon the application of an electric field. The electric field polarizes each of the droplets in the field direction. The polarization causes the drops to deform and drives a dipolar attraction which forces them to approach each other and coalesce. Many technologies use electric fields to manipulate fluid dispersions. Electrocoalescence is an essential unit operation for separating water droplets in a crude oil. This water in oil emulsion is stabilized by surfactants, such as asphaltenes, resins and …
Microfluidic Study Of The Electrocoalescence Of Aqueous Droplets In Crude Oil, Thomas Leary, Mohsen Yeganeh, Charles Maldarelli
Microfluidic Study Of The Electrocoalescence Of Aqueous Droplets In Crude Oil, Thomas Leary, Mohsen Yeganeh, Charles Maldarelli
Publications and Research
In electrocoalescence, an electric field is applied to a dispersion of conducting water droplets in a poorly conducting oil to force the droplets to merge in the direction of the field. Electrocoalescence is used in petroleum refining to separate water from crude oil and in droplet-based microfluidics to combine droplets of water in oil and to break emulsions. Using a microfluidic design to generate a two-dimensional (2D) emulsion, we demonstrate that electrocoalescence in an opaque crude oil can be visualized with optical microscopy and studied on an individual droplet basis in a chamber whose height is small enough to make …
Capillary Forces And Wetting Dynamics By Diffuse-Interface Modeling, Fanny Thomas
Capillary Forces And Wetting Dynamics By Diffuse-Interface Modeling, Fanny Thomas
Dissertations and Theses
Wetting phenomena underlie many natural and industrial processes, from the proper functioning of the lungs to the thin coating of surfaces. The three-phase interactions involved at microscopic scales play a critical role. Adding solid particles to an emulsion, for example, can drastically change the flow behavior due to capillary bridging between the particles. The study of these three-phase systems is especially relevant to the petroleum industry, where gas hydrates forming large clusters in subsea pipelines during crude oil transportation is a major concern. The dynamics of such systems is also of great interest from a fundamental perspective. Indeed describing non-equilibrium …
Microfluidic Study Of Gravity-Driven Drainage And Coalescence Of Aqueous Two Dimensional Foams, Justin D. Heftel
Microfluidic Study Of Gravity-Driven Drainage And Coalescence Of Aqueous Two Dimensional Foams, Justin D. Heftel
Dissertations and Theses
Foams, a two-phase dispersion, are staples of the cosmetic, personal care, petroleum, pharmaceutical, and other industries. Central to these applications is the stability of the dispersion against separation. Foams break down by two mechanisms: the first is bubble coalescence, which is driven by the gravity drainage of the continuous phase. The drainage acts to push the bubbles against each other, and leads to the formation of thin lamellae, which break and cause the coalescence. The second is the mass transfer of the dispersed phase through the continuous phase, which is caused by the difference in pressures between the bubbles and …
Developing A 3d In Vitro Model By Microfluidics, Hung-Ta Chien
Developing A 3d In Vitro Model By Microfluidics, Hung-Ta Chien
Dissertations and Theses
In vitro tissue models play an important role in providing a platform that mimics the realistic tissue microenvironment for stimulating and characterizing the cellular behavior. In particular, the hydrogel-based 3D in vitro models allow the cells to grow and interact with their surroundings in all directions, thus better mimicking in vivo than their 2D counterparts. The objective of this thesis is to establish a 3D in vitro model that mimics the anatomical and functional complexity of the realistic cancer microenvironment for conveniently studying the transport coupling in porous tissue structures. We pack uniform-sized PEGDA-GelMA microgels in a microfluidic chip to …
Coalescence-Induced Jumping Of Droplet: Inertia And Viscosity Effects, Samaneh Farokhirad, Jeffrey F. Morris, Taehun Lee
Coalescence-Induced Jumping Of Droplet: Inertia And Viscosity Effects, Samaneh Farokhirad, Jeffrey F. Morris, Taehun Lee
Publications and Research
The problem of coalescence-induced self-propelled jumping of droplet is studied using three-dimensional numerical simulation. The focus is on the effect of inertia and in particular the effect of air density on the behavior of the merged droplet during jumping. A lattice Boltzmann method is used for two identical, static micro-droplets coalescing on a homogeneous substrate with contact angle ranging from 0◦ to 180◦. The results reveal that the effect of air density is significant on detachment of the merged droplet from the substrate at the later stage of the jumping process; the larger the air density, the larger the jumping …
A Study On The Heavy Crude Oil Viscosity Reduction With The Dissolution Of Nitrogen And Carbon Dioxide, Abdurahman Ajumobi
A Study On The Heavy Crude Oil Viscosity Reduction With The Dissolution Of Nitrogen And Carbon Dioxide, Abdurahman Ajumobi
Dissertations and Theses
World's energy challenges would be greatly improved upon if half of the world's heavy oil and extra heavy oil could be made to ow in pipelines. Viscosity reduction of heavy oils is the key to solving this problem. In this study, aside from injecting pure nitrogen and pure carbon dioxide separately into the oil, two different compositions of the mixture of the two gases were also injected. In the first mixture, varied quantities of the two gases were used; 62:5%, 82:2% and 86:4% of the mixture was nitrogen while 37:5%, 17:8% and 13:6% was carbon dioxide at total test pressures …
Effect Of Ionic Liquid Electrolytes In Dsscs With Titanium Dioxide (Tio2) Inverse Opal Structures, Naomi S. Ramesar
Effect Of Ionic Liquid Electrolytes In Dsscs With Titanium Dioxide (Tio2) Inverse Opal Structures, Naomi S. Ramesar
Dissertations and Theses
Dye-sensitized solar cells (DSSC) are low-cost alternatives to conventional solar cells that can work well in low-light conditions. Despite considerable study on improving the efficiency of DSSCs, the current liquid electrolyte cell has plateaued at a conversion efficiency of ~ 12%. A major problem with these cells regarding their applicability is the low viscosity and high volatility of the toxic electrolyte, i.e., acetonitrile, which cause leakage and volatilization. We propose that using ionic liquids (ILs), which are more viscous, less volatile, and conductive, may be more suitable electrolytes. However, one unwanted side effect of the higher viscosity of the ILs …