Complex Fluids Commons^™

A Novel Rheological Technique To Measure The Yield Stress In Equibiaxial Elongation, Asher Segal

Theses

Yield stress measurement in non-Newtonian fluids, particularly under complex flow conditions such as equibiaxial elongation, remains a significant challenge in experimental rheology. This work presents the development of a novel method, Continuous Lubricated Squeezing Flow (CLSF), designed to quantify the normal yield stress of viscoelastic materials while minimizing boundary artifacts.

The CLSF method was implemented and validated using Carbopol 940, a model yield-stress gel, at concentrations of 1 wt% and 2 wt%. Comparative shear rheology was first performed to establish baseline yield stresses and verify sample integrity. CLSF experiments were then conducted over controlled flow rate increments and gap distances …

Rheological, Interfacial, And Filtration Behavior Of Lignocellulosic Nanomaterials In Suspension And Emulsion Drilling Fluids, Meen Sung Koo

LSU Doctoral Dissertations

In recent years, the rheological aspects of suspensions/emulsions applied by cellulose nanomaterials (CNMs) have been gained considerable interests due to high gel-forming properties ascribed by hydrophilicity, crystallinity, ease functionalization, and high aspect ratio. Introducing residual lignin in CNMs (LCNMs) seemed to be capable of achieving various advantages in the application of CNMs ascribed by hydrophobicity, binding effects, and abundant aromatic groups derived from complexity of lignin. This dissertation dedicates to the characterizations of (L)CNMs, and rheological properties of (L)CNMs applied fluids (i.e., suspension and emulsion). In the suspension system, the presence of lignin in LCNMs decreased gel strength, viscosity, and …

Fundamental Study Of Nonlinear Electrophoresis, Joseph Armakan Bentor

All Dissertations

Classical electrophoretic theory describes the linear response of particles suspended in Newtonian fluids under weak electric fields. When the electric field exceeds this weak limit, a nonlinear response arises due to non-uniform surface conduction over the curved particles. This nonlinear behavior introduces dependencies on fluid and particle properties not considered in the classical theory, offering potential advantages for microfluidic particle manipulation. While this phenomenon has been extensively studied theoretically and numerically in Newtonian fluids, experimental investigations have been relatively limited.

Fluid rheology can significantly alter particle dynamics under applied electric fields. Rheological properties like shear-thinning and elasticity which are not …

Characterization Of Tunable And Responsive Functionalized Cellulose Nanofiber (Cnf) Gels With Applications As A 3d Bioprinting Ink, Charles Joseph Jouaneh

Senior Honors Projects

No abstract provided.

Investigating The Rheological Behavior Of A Simple Yield Stress Fluid Under Shear Flows, Francesco Accetta

Theses

Many soft materials display unique and complex rheological behavior characterized by a transition from a solid-like to a fluid-like state upon the application of a force that exceeds the threshold to flow, known as the yield stress. Yield stress fluids are found in a wide range of commonly encountered materials including microgels, emulsions, and foams, and have been widely studied by rheologists over the last several decades. Carbopol is a popular polymeric microgel system as it displays simple, non-thixotropic rheological behavior and is typically seen as an ideal yield stress fluid. Previous research has demonstrated the reproducible behavior of shear …

Vermiculations In Painted Caves: New Inputs From Laboratory Experiments And Field Observations, Perrine Freydier, Eric Weber, Jérôme Martin, Pierre-Yves Jeannin, Béatrice Guerrier, Frédéric Doumenc

International Journal of Speleology

Vermiculations are aggregates of small particles commonly found on cave walls. They are a major concern for the conservation of painted caves, as they can potentially alter valuable prehistoric cave paintings. A previous rheological study of fine sediment deposits on cave walls revealed that this material can undergo a solid-to-liquid transition triggered by variations in the chemical composition of the water film on the wall. Such a transition could occur at the origin of vermiculations by allowing the sediment to flow under low mechanical stress. In this work, we provide quantitative information on the conditions leading to this transition and …

Effect Of Surfactant, Oil:Water Ratio And Temperature On The Rheology Of Emulsion-Suspension Complex Fluids: Implications For Oil-Based Drilling Fluids, Gilles Landry Numkam

LSU Doctoral Dissertations

Drilling fluids are non-Newtonian mixtures that play a critical role in the timely and successful completion of oil and gas wells. In the particular case of offshore operations, proper design of drilling fluids is of paramount importance in the constant quest to lower break-even prices. Most downhole problems are directly or in-directly related to the rheological and physical properties of drilling fluids, thereby calling for a better understanding of the underlying changes of these properties with respect to drilling fluid composition and external conditions.

The current stance in the design of drilling fluids involves the selection of components and their …

Microstructure And Rheology Of Carbon Nanotubes At Air-Water Interfaces, Charles D. Young

Honors Scholar Theses

This work characterizes the material properties of carbon nanotubes at air-water interfaces for potential use in creating stable emulsions. Properties such as length, aspect ratio, contact angle, microstructural ordering, surface pressure, compression and shear elastic moduli, stresses, surface viscosities and non-linearity are explored. Challenges such as deviation from a classical analysis of monolayers are encountered in the form of aggregation, mechanical contributions, and interface relaxation. These factors are taken into account to explain experimental measurements and trends. Ultimately, existing models for more homogeneous systems are resolved with observations to offer insight and areas of promise moving forward.