Strong-field magnetotransport of two-phase disordered media in two and three dimensions: Exact and approximate results

2006 ◽  
Vol 74 (9) ◽  
Author(s):  
Ronen Magier ◽  
David J. Bergman
Keyword(s):  
Strong Field ◽  
Three Dimensions ◽  
Disordered Media ◽  
Two Phase

Universality classes and fluctuations in disordered systems

1992 ◽  
Vol 437 (1899) ◽  
pp. 67-83 ◽  
Keyword(s):  
Disordered Systems ◽  
Classification Scheme ◽  
Three Dimensions ◽  
Disordered Media ◽  
Transmission Matrix ◽  
Universal Scaling ◽  
Transmission Coefficients ◽  
Universality Classes ◽  
Current Flows ◽  
Amplitude Transmission

Waves transmitted through disordered media show increasing fluctuations with thickness of material so that averages of different properties of the wavefield have very different scaling with thickness traversed. We have been able to classify these properties according to a scheme that is independent of the nature of the medium, such that members of a class have a universal scaling independent of the nature of the medium. We apply this result to trace ( T L T † L ) M , where T L is the amplitude transmission matrix. The eigenfunctions of T L T † L define a set of channels through which the current flows, and the eigenvalues are the corresponding transmission coefficients. We prove that these coefficients are either ≈ 0 or ≈ 1. As L increases more channels are shut down. This is the maximal fluctuation theorem : fluctuations cannot be greater than this. We expect that our classification scheme will prove of further value in proving theorems about limiting distributions. We show by numerical simulations that our theorem holds good for a wide variety of systems, in one, two and three dimensions.

Analysis of Two-Phase Air/Water Bubbly Flow Experiment

2002 ◽  
Author(s):  
Donald R. Todd ◽  
Yassin A. Hassan ◽  
Javier Ortiz-Villafuerte
Keyword(s):  
Particle Image ◽  
Bubbly Flow ◽  
Continuous Phase ◽  
Three Dimensions ◽  
Dispersed Phase ◽  
Two Dimensional ◽  
Two Phase ◽  
Image Velocimetry ◽  
Flow Experiment ◽  
Shadow Image Velocimetry

Two different techniques, the Particle Image Velocimetry (PIV) and the Shadow-Image Velocimetry (SIV) techniques have been used to capture detailed two-phase bubbly flow experimental data. The PIV has provided a two-dimensional velocity field of the liquid phase for analysis of the continuous phase. The SIV has utilized to reconstruct the bubble shape and velocity of the dispersed phase in three-dimensions.

Mid-gap invasion in two-layer slot coating

2009 ◽  
Vol 631 ◽  
pp. 397-417 ◽  
Author(s):  
JAEWOOK NAM ◽  
MARCIO S. CARVALHO
Keyword(s):  
Free Surface Flows ◽  
Operating Conditions ◽  
Three Dimensions ◽  
Separation Point ◽  
Complex Flow ◽  
Two Phase ◽  
Navier Stokes Equation ◽  
Slot Coating ◽  
Die Surface ◽  
Flow States

Multi-layer, continuous liquid coating is the most efficient way to manufacture films that require more than one layer for optimal performance. Dual-layer slot coating is one of different coating methods largely used to deposit two thin, uniform liquid layers on to a moving substrate. The two liquid phases are separated by an inter-layer that starts at the separation point (or line, in three dimensions) attached to the die surface. The stability of the two-phase flow and the location of the separation point are directly related to the quality of the final product. Ideally, the separation point should be attached to the downstream corner of the mid die piece of a dual slot-coating die. However, its location may change as operating conditions vary, leading to undesired flow states, with microvortices and periodic oscillation. The movement of the separation point from its desired location along the die surface is usually referred to as mid-gap invasion and can be associated with the onset of coating defects. It is crucial to determine the set of flow conditions at which it occurs. We study the evolution of the separation-point location and the inter-layer configuration as a function of operating conditions by flow visualization and by solving the two-dimensional Navier–Stokes equation for free-surface flows. The results reveal two different mechanisms for mid-gap invasion, depending on the viscosity ratio of the two liquid layers. They also show that the most critical parameter responsible for the onset of mid-gap invasion is the bottom-layer wet thickness (flow rate). Although the movement of the separation point involves an evolution of complex flow states, a simple but accurate criterion based on rectilinear flow approximation is proposed.

scholarly journals Simulated Microstructural Evolution and Design of Porous Sintered Wicks

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Karthik K. Bodla ◽  
Suresh V. Garimella
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Transport Properties ◽  
Effective Thermal Conductivity ◽  
Surface Area ◽  
Microstructural Evolution ◽  
Ad Hoc ◽  
Three Dimensions ◽  
Two Phase ◽  
Sintering Kinetics

Porous structures formed by sintering of powders, which involves material-bonding under the application of heat, are commonly employed as capillary wicks in two-phase heat transport devices such as heat pipes. These sintered wicks are often fabricated in an ad hoc manner, and their microstructure is not optimized for fluid and thermal performance. Understanding the role of sintering kinetics—and the resulting microstructural evolution—on wick transport properties is important for fabrication of structures with optimal performance. A cellular automaton model is developed in this work for predicting microstructural evolution during sintering. The model, which determines mass transport during sintering based on curvature gradients in digital images, is first verified against benchmark cases, such as the evolution of a square shape into an area-preserving circle. The model is then employed to predict the sintering dynamics of a side-by-side, two-particle configuration conventionally used for the study of sintering. Results from previously published studies on sintering of cylindrical wires are used for validation. Randomly packed multiparticle configurations are then considered in two and three dimensions. Sintering kinetics are described by the relative change in overall surface area of the compact compared to the initial random packing. The effect of sintering parameters, particle size, and porosity on fundamental transport properties, viz., effective thermal conductivity and permeability, is analyzed. The effective thermal conductivity increases monotonically as either the sintering time or temperature is increased. Permeability is observed to increase with particle size and porosity. As sintering progresses, the slight increase observed in the permeability of the microstructure is attributed to a reduction in the surface area.

scholarly journals Measuring a University’s Image: Is Reputation an Influential Factor?

2021 ◽  
Vol 12 (1) ◽  
pp. 19
Author(s):  
Belén Gutiérrez-Villar ◽  
Purificación Alcaide-Pulido ◽  
Mariano Carbonero-Ruz
Keyword(s):  
Higher Education ◽  
Private University ◽  
University Education ◽  
Influential Factor ◽  
Three Dimensions ◽  
Higher Education Management ◽  
Two Phase ◽  
Education Management ◽  
Confirmatory Factor ◽  
The University

Today, the higher education sector can be considered a market and, within it, private university education is a common marketable service in the literature on higher education management. Research on the analysis of the variables that generate the university image has been the subject of numerous investigations. Although there is no generally accepted definition, most authors approach the measurement of image through multi-factor scales, with variables relating to functional and psychological elements. This research aims to contribute to study of the most determinant variables in measuring a product’s image, assessing especially the effect of the reputation construct. This was done through measuring the image of the “private university” product as perceived by citizens of Andalusia, based on a standardized model with three dimensions—functional and affective aspects and reputation. After adapting and validating the questionnaire, a two-phase procedure is performed with double validation through exploratory and confirmatory factor analysis. The results show an adapted scale valid for measuring the image of a generic product; with presentation and discussion of a series of advantages of incorporating reputation and measuring image through models with three dimensions. This article goes deeper into the possible influence of reputation as a determinant factor in measuring image, an assumption arising from some models for measuring image, something that so far has not been sufficiently contrasted.

Pulsating localised fluid expulsions

2020 ◽  
Author(s):  
Ludovic Räss ◽  
Nina S.C. Simon ◽  
Yury Y. Podladchikov
Keyword(s):  
Gas Flow ◽  
Two Phase Flow ◽  
Porous Matrix ◽  
Pore Fluid ◽  
Three Dimensions ◽  
Model Parameters ◽  
Phase Flow ◽  
Two Phase ◽  
Natural Systems ◽  
Natural Outcome

<p>A wide variety of fluid-rich natural systems exhibit a distinct pulsating signature on geophysical measurements. Identifying the processes leading to these observed pulses are key to further understand important multi-scale and multi-physics valve-like dynamics in natural environments such as gas flow in volcanic systems, magma transport in the crust, tremors and slip or subsurface flow migration. These natural two-phase systems share common features as they can be described as viscously deforming saturated porous media. They exhibit a time-dependant deformation of their porous matrix, buoyant pore-fluid, an effective pressure dependant bulk viscosity and a nonlinear porosity-permeability relation.</p><p>We here investigate the role of coupled hydro-mechanical processes to trigger pulsating localised fluid expulsions. We show that the pulsating regime may be a natural outcome of the interactions between a viscously deforming porous matrix and a nonlinear pore-fluid flow. We rely on high-resolution direct numerical two-phase flow calculations in three dimensions to explore what parameters control the main characteristics of the pulsating signal. We are particularly interested in how amplitudes, wave lengths and frequencies of the signal relate to the input model parameters.</p><p>We show that repeated fluid pulses are a natural outcome of the coupled Stokes and Darcy equations within the nonlinear viscous two-phase flow regime. We discuss the relevance of our findings in light of the valve-like behaviour in a variety of natural fluid-rich environments. We propose to use the characteristic of the pulsating signal to gain further insight in the dynamics of complex natural systems.</p>

scholarly journals Thermodynamically consistent Navier–Stokes–Cahn–Hilliard models with mass transfer and chemotaxis

2017 ◽  
Vol 29 (4) ◽  
pp. 595-644 ◽  
Author(s):  
KEI FONG LAM ◽  
HAO WU
Keyword(s):  
Mass Transfer ◽  
Chemical Potential ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Navier Stokes ◽  
Fluid Viscosity ◽  
Well Posedness ◽  
Global Weak Solutions ◽  
Two Phase ◽  
Model Variant

We derive a class of Navier–Stokes–Cahn–Hilliard systems that models two-phase flows with mass transfer coupled to the process of chemotaxis. These thermodynamically consistent models can be seen as the natural Navier–Stokes analogues of earlier Cahn–Hilliard–Darcy models proposed for modelling tumour growth, and are derived based on a volume-averaged velocity, which yields simpler expressions compared to models derived based on a mass-averaged velocity. Then, we perform mathematical analysis on a simplified model variant with zero excess of total mass and equal densities. We establish the existence of global weak solutions in two and three dimensions for prescribed mass transfer terms. Under additional assumptions, we prove the global strong well-posedness in two dimensions with variable fluid viscosity and mobilities, which also includes a continuous dependence on initial data and mass transfer terms for the chemical potential and the order parameter in strong norms.

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