Download or read book Dynamic Contact Angles and Wetting Front Instability in Soils written by Christine E. Baver and published by . This book was released on 2013 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamic contact could provide a mechanism for initiating the instability of wetting fronts and the formation of gravity fingers/columns in porous media. To study those dynamic contact angles when gravity effects are present, rectangular capillary tubes are used to facilitate the observation of the complete interface without geometric distortion. Results show that if the dynamic contact angle minus the static contact angle is used, we obtain good agreement with previous observations. In addition, we show that in our experiments, unlike previous observations, contact angles are independent of capillary size. It also points out a way to calculate the capillary pressure at the wetting front as a function of the flux in the finger and grain size diameter.

Download or read book Wetting Front Instability in Layered Soils with Low Infiltration Rates written by Dusica Jevremovic and published by . This book was released on 1995 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Unstable Wetting in Homogeneous Soils Under Continuous Infiltration written by John S. Selker and published by . This book was released on 1991 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Wetting Front Instability in Layered Soils written by Seyed Ali Cheraghi and published by . This book was released on 1987 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis and Verification of a Wetting Front Model for Infiltration Into Soils written by Cindy Sue-Shih Kao and published by . This book was released on 1996 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Wetting Front Instability in Uniform Soils Under Low Infiltration Rates written by Tzung-mow Yao and published by . This book was released on 1993 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of Wetting Front Instability in Layered Porous Media written by Robert J. Glass and published by . This book was released on 1985 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fractal Analysis of Wetting Front Instability in Unsaturated Soil written by Wen-Lian Tim Chang and published by . This book was released on 1992 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Prediction of Wetting Front Instability in Homogeneous Soils written by Tzung-mow Yao and published by . This book was released on 1998 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Moving Contact Lines Wetting Transitions and Interfacial Instabilities in Confined Environments written by Amir Alizadeh Pahlavan and published by . This book was released on 2018 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: Immiscible fluid flows are ubiquitous in nature and industry, from multiphase-flow phenomena on geologic scales such as CO2 sequestration and methane venting from seafloor sediments to bubble/drop/emulsion generation in microfluidic techniques. All these flows are inherently multi-scale, from the intermolecular interactions on the nanometer scale in the vicinity of contact lines, where fluid phases meet the surrounding solid surface, to the micrometer scale of the confinement in a pore or microfluidic device, and finally to kilometer scale of the natural geologic phenomena. The multi-scale nature of immiscible fluid flows combined with the inherent disorder present in many natural or industrial systems renders description of these flows a formidable task. Here, using a combination of experimental observations and theoretical modeling we show that the interplay between confinement and contact line motion leads to novel and non-trivial consequences on the dynamics and instability of immiscible fluid fronts. We first present a theoretical model for thin-film flows on solid surfaces in the partial wetting regime and show that a self-consistent description of free energy of this system at equilibrium leads to a Cahn-Hilliard form with an effective height-dependent surface tension due to the interniolecular forces in the vicinity of the contact line. Within the framework of non-equilibrium thermodynamics, we then study the consequences of this new form of free energy on the spreading of drops and dewetting of thin films in the partial wetting regime. We show that on macroscopic scales, our model recovers the classic hydrodynamic Cox-Voinov description of moving contact lines and is consistent with experimental observations. We further show that on the microscopic scale our model is consistent with the molecular kinetic theory, therefore bridging the gap between the two descriptions across the scales. We finally show that our model captures the dynamics of nanometric dewetting thin films in spinodal and nucleation regimes as well as their long-time coarsening behavior and brings the theoretical predictions closer to the previous experimental observations. We then revisit the classic Taylor-Bretherton problem in the partial wetting regime, where air displaces a highly viscous liquid in a capillary tube. In contrast with the classic results for complete wetting, we show that the presence of a moving contact line induces a wetting transition at a critical capillary number that is contact angle dependent. Beyond wetting transition, a film of the defending liquid coats the tube walls. The entrained liquid film immediately starts receding along the tube wall, forming a growing dewetting rim behind the contact line, which finally leads to the breakup of the bubble. The bubble pinch-off is an example of singularity formation, where separation of length scales close to the point of singularity are expected to lead to self-similar and universal dynamics. We show that the breakup of a bubble confined in a capillary tube undergoes a sequence of two distinct self-similar regimes even though the balance remains between viscous and surface-tension forces. While the breakup of a bubble in an unbounded reservoir is known to be non-universal, we demonstrate that the presence of the early-time self-similar regime in a confined system effectively erases the system's memory and restores universality to bubble breakup. We then revisit the classic Saffinan-Taylor instability in the imbibition regime, where a more wetting and less viscous liquid displaces a less wetting and more viscous liquid in a radial Hele-Shaw cell (two plates separated by a small gap). We show that the wetting liquid invades the cell in the form of a thin-film front, which becomes unstable and leads to a viscous fingering pattern. To gain an understanding of the front dynamics, we develop a thin-film model, which predicts the base state of the invading thin films to be an undercompressive shock, which has previously been shown to lead to stable fronts. Using linear stability analysis and nonlinear simulations, we show that consistent with our experimental observations the thin film front in a Hele-Shaw cell is unstable. The instability here is due to the pressure coupling between the two fluid flows in a confined domain. We further show that the scaling of the wavelength of instability in thin-film front is different from the Saffman-Taylor instability, suggesting that it belongs to a new pattern formation class. In the final part of this thesis, we explore how the interplay between wetting and disorder influences the pattern formation. We introduce disorder into the Hele-Shaw system by making one of the surfaces randomly rough. In particular, we show that in the imbibition regime aside from the primary thin films that we observed in smooth cells, secondary thin films of the scale of roughness appear. These secondary films wick into the crevices of the rough surface with a diffusive dynamics and change the effective wettability of the medium. We therefore show that disorder on the micro-scale affects the macroscopic morphology of unstable fluid fronts.

Download or read book Optimal Stability of Variable Viscosity Displacements in Porous Media written by Sheldon Burt Gorell and published by . This book was released on 1984 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Annual Review of Fluid Mechanics written by and published by Annual Reviews. This book was released on 1987 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides abstracts and full text to articles on fluid mechanics.

Download or read book Soil Water Repellency written by C.J. Ritsema and published by Elsevier. This book was released on 2012-12-02 with total page 359 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has become clear that soil water repellency is much more wide-spread than formerly thought. Water repellency has been reported in most continents of the world for varying land uses and climatic conditions. Soil water repellency often leads to severe runoff and erosion, rapid leaching of surface-applied agrichemicals, and losses of water and nutrient availability for crops. At present, no optimum management strategies exist for water repellent soils, focusing on minimizing environmental risks while maintaining crop production. The book starts with a historical overview of water repellency research, followed by seven thematic sections covering 26 research chapters. The first section discusses the origin, the second the assessment, and the third the occurrence and hydrological implications of soil water repellency. The fourth section is devoted to the effect of fire on water repellency, section five deals with the physics and modeling of flow and transport in water repellent soils, section six presents amelioration techniques and farming strategies to combat soil water repellency, and section seven concludes the book with an extensive bibliography on soil water repellency.

Download or read book Introduction to Environmental Soil Physics written by Daniel Hillel and published by Elsevier. This book was released on 2003-12-17 with total page 511 pages. Available in PDF, EPUB and Kindle. Book excerpt: An abridged, student-oriented edition of Hillel's earlier published Environmental Soil Physics, Introduction to Environmental Soil Physics is a more succinct elucidation of the physical principles and processes governing the behavior of soil and the vital role it plays in both natural and managed ecosystems. The textbook is self-contained and self-explanatory, with numerous illustrations and sample problems. Based on sound fundamental theory, the textbook leads to a practical consideration of soil as a living system in nature and illustrates the influences of human activity upon soil structure and function. Students, as well as other readers, will better understand the importance of soils and the pivotal possition they occupy with respect to careful and knowledgeable conservation. Written in an engaging and clear style, posing and resolving issues relevant to the terrestrial environment Explores the gamut of the interactions among the phases in the soil and the dynamic interconnection of the soil with the subterranean and atmospheric domains Reveals the salient ideas, approaches, and methods of environmental soil physics Includes numerous illustrative exercises, which are explicitly solved Designed to serve for classroom and laboratory instruction, for self-study, and for reference Oriented toward practical problems in ecology, field-scale hydrology, agronomy, and civil engineering Differs from earlier texts in its wider scope and holistic environmental conception

Download or read book Multiphase Flow in Permeable Media written by Martin J. Blunt and published by Cambridge University Press. This book was released on 2017-02-16 with total page 503 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a fundamental description of multiphase fluid flow through porous rock, based on understanding movement at the pore, or microscopic, scale.

Download or read book Capillary Flows with Forming Interfaces written by Yulii D. Shikhmurzaev and published by CRC Press. This book was released on 2007-09-14 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capillary Flows with Forming Interfaces explores numerous theoretical problems that arise in the mathematical description of capillary flows. It focuses on developing a unified approach to a variety of seemingly very different capillary flows of practical importance where classical fluid mechanics leads to nonphysical results. The book begin

Download or read book Unsaturated Soils Research Applications written by Nasser Khalili and published by CRC Press. This book was released on 2014-06-05 with total page 1872 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unsaturated Soils: Research and Applications contains 247 papers presented at 6th International Conference on Unsaturated Soils (UNSAT2014, Sydney, Australia, 2-4 July 2014). The two volumes provide an overview of recent experimental and theoretical advances in a wide variety of topics related to unsaturated soil mechanics:- Unsaturated Soil Behavi