Linear interfacial stability of a core-annular flow with application to liquid-liquid displacements in small pores.
Item
-
Title
-
Linear interfacial stability of a core-annular flow with application to liquid-liquid displacements in small pores.
-
Identifier
-
AAI9130315
-
identifier
-
9130315
-
Creator
-
Georgiou, Evangelos.
-
Contributor
-
Advisers: David S. Rumschitzki | Charles Maldarelli
-
Date
-
1991
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Engineering, Chemical
-
Abstract
-
In the first problem I examine the case of a film surrounding a dielectric-fluid core in a tube in the presence of double layers of charges at the film-core and at the film-tube interfaces. In the absence of electrostatic forces, waves larger than the unperturbed interface circumference are unstable and those shorter are stable due to capillarity. Two cases are examined: (i) double layer repulsion and (ii) double layer attraction. In the first case, double layer repulsion and surface tension lowering stabilize the destabilizing action of the surface tension, and a window of stability can exist. In the case of double layers of opposite signs, double layer attraction destabilizes the system. Finally, for the case of a core bounded by an infinite electrolyte, surface tension lowering stabilizes the destabilizing action of the circumferential component of the surface tension force and destabilizes the longitudinal one. As a result the thread can become unstable to waves even shorter than the undisturbed interface circumference.;In the second problem I examine the case of a gravity and/or pressure-driven CAF in the limit of small film thickness in the presence of viscosity and density stratification in addition to tension. Asymptotic expansions lead to analytical expressions that govern the linear stability of the system. A glance at the resulting expression shows how to order the parameters to bring out different effects. For a moderate flow three canonical regimes merit study: (i) large surface tension in the presence of viscosity and density stratification and moderate or low surface tension with density stratification in the (ii) presence or (iii) absence of viscosity stratification. In the first regime the stabilizing action of the viscosity stratification (with the less viscous fluid in the film) can overcome capillarity while the density difference is merely a second order effect. In the case of moderate surface tension and in the absence of viscosity stratification, the density difference along is able to stabilize capillarity. Finally, when the less viscous fluid is in the core, viscosity stratification has a purely destabilizing effect and as a result the system becomes unstable to waves even shorter than the undisturbed interface circumference.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
