scholarly journals AGN Dusty Tori as a Clumpy Two-Phase Medium: the 10 μm Silicate Feature

2011 ◽  
Vol 20 (3) ◽  
Author(s):  
Marko Stalevski ◽  
Jacopo Fritz ◽  
Maarten Baes ◽  
Theodoros Nakos ◽  
Luka Č. Popović
Keyword(s):  
Three Dimensional ◽  
Galactic Nuclei ◽  
Infrared Emission ◽  
Spectral Energy ◽  
Two Phase ◽  
Random Arrangement ◽  
Wide Range ◽  
Phase Medium ◽  
Silicate Feature ◽  
Dust Distribution

AbstractWe investigated the emission of active galactic nuclei dusty tori in the infrared domain, with a focus on the 10 μm silicate feature. We modeled the dusty torus as a clumpy two-phase medium with high-density clumps and a low-density medium filling the space between the clumps. We used a three-dimensional radiative transfer code to obtain spectral energy distributions and images of tori at different wavelengths. We calculated a grid of models for different parameters and analyzed the influence of these parameters on the shape of the mid-infrared emission. A corresponding set of clumps-only models and models with a smooth dust distribution is calculated for comparison. We found that the dust distribution, the optical depth and a random arrangement of clumps in the innermost region, all have an impact on the shape and strength of the silicate feature. The 10 μm silicate feature can be suppressed for some parameters, but models with smooth dust distribution are also able to produce a wide range of the silicate feature strength.

Numerical Analysis of Cavitation Instabilities Arising in the Three-Blade Cascade

2004 ◽  
Vol 126 (3) ◽  
pp. 419-429 ◽  
Author(s):  
Yuka Iga ◽  
Motohiko Nohml ◽  
Akira Goto ◽  
Toshiaki Ikohagi
Keyword(s):  
Numerical Method ◽  
High Speed ◽  
Homogeneous Model ◽  
Rotating Stall ◽  
Two Phase ◽  
Wide Range ◽  
Phase Medium ◽  
Long Time ◽  
Entire Flow ◽  
Locally Homogeneous

Three types of cavitation instabilities through flat plate cascades, which are similar to “forward rotating cavitation,” “rotating-stall cavitation” and “cavitation surge” occurring in high-speed rotating fluid machinery, are represented numerically under the three-blade cyclic condition. A numerical method employing a locally homogeneous model of compressible gas-liquid two-phase medium is applied to solve the above flow fields, because this permits the entire flow field inside and outside the cavity to be treated through only one system of governing equations. In addition, the numerical method suites to analyze unsteady cavitating flow with a long time evolution. From the calculated results of the present numerical simulation with wide range of cavitation number and flow rate, we obtain a cavitation performance curve of the present three-blade cyclic cascade, analyze the aspects of unsteady cavitation, and discuss the characteristics and mechanisms of cavitation.

scholarly journals Growth model for large branched three-dimensional hydraulic crack system in gas or oil shale

2016 ◽  
Vol 374 (2078) ◽  
pp. 20150418 ◽  
Author(s):  
Viet T. Chau ◽  
Zdeněk P. Bažant ◽  
Yewang Su
Keyword(s):  
Solid Phase ◽  
Three Dimensional ◽  
Cohesive Crack ◽  
Rock Joints ◽  
Recent Analysis ◽  
Band Model ◽  
Two Phase ◽  
Strength Limit ◽  
Crack Wall ◽  
Phase Medium

Recent analysis of gas outflow histories at wellheads shows that the hydraulic crack spacing must be of the order of 0.1 m (rather than 1 m or 10 m). Consequently, the existing models, limited to one or several cracks, are unrealistic. The reality is 10 5 –10 6 almost vertical hydraulic cracks per fracking stage. Here, we study the growth of two intersecting near-orthogonal systems of parallel hydraulic cracks spaced at 0.1 m, preferably following pre-existing rock joints. One key idea is that, to model lateral cracks branching from a primary crack wall, crack pressurization, by viscous Poiseuille-type flow, of compressible (proppant-laden) frac water must be complemented with the pressurization of a sufficient volume of micropores and microcracks by Darcy-type water diffusion into the shale, to generate tension along existing crack walls, overcoming the strength limit of the cohesive-crack or crack-band model. A second key idea is that enforcing the equilibrium of stresses in cracks, pores and water, with the generation of tension in the solid phase, requires a new three-phase medium concept, which is transitional between Biot’s two-phase medium and Terzaghi’s effective stress and introduces the loading of the solid by pressure gradients of diffusing pore water. A computer program, combining finite elements for deformation and fracture with volume elements for water flow, is developed to validate the new model. This article is part of the themed issue ‘Energy and the subsurface’.

An Efficient CFD Model for Air/Particle Saltating Flows

2002 ◽  
Author(s):  
S. Ji ◽  
A. G. Gerber ◽  
A. C. M. Sousa
Keyword(s):  
Particle Concentration ◽  
Particle Surface ◽  
Three Dimensional ◽  
Phase System ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Dynamics Model ◽  
Three Dimensional Flow ◽  
Two Phase ◽  
Wide Range

The study reports on the development of a computational-fluid-dynamics model is presented suitable for computationally efficient evaluation of particle transport along loose surfaces. These surfaces can be described within the context of an interaction with a two-phase air/particle mixture in a state of combined suspension and saltation. The results suggest an approach for approximating the two-phase system with coupling to a moving surface, along with the inclusion of impact and entrainment fluxes at the surface that is generally extendable to a wide range of particle/surface conditions. The model results are compared to available experimental data on particle concentration profiles along saltating surfaces, and applied to geometry involving complex three-dimensional flow to show the generality of the approach.

FMM/GPU Accelerated BEM Simulations of Emulsion Flow in Microchannels

2013 ◽  
Author(s):  
Olga A. Abramova ◽  
Yulia A. Itkulova ◽  
Nail A. Gumerov
Keyword(s):  
Oil Recovery ◽  
Large Scale ◽  
Heterogeneous Computing ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Computational Techniques ◽  
Graphics Processors ◽  
Two Phase ◽  
Scalable Algorithm ◽  
Wide Range

Modeling of motion of two-phase liquids in microchannels of different shape is needed for a variety of industrial applications, such as enhanced oil recovery, advanced material processing, and biotechnology. Development of efficient computational techniques is required for understanding the mechanisms of many effects in “liquid-liquid” systems, such as the jamming of emulsion flows in microchannels and blood cell motion in capillaries. In the present study, a mathematical model of a three-dimensional flow of a mixture of two Newtonian liquids of a droplet structure in microchannels at low Reynold’s numbers is considered. The computational approach is based on the boundary element method accelerated both via an advanced scalable algorithm (FMM), and via utilization of a heterogeneous computing architecture (multicore CPUs and graphics processors). To solve large scale problems flexible GMRES solver is developed. Example computations are conducted for dynamics of many deformable drops of different sizes in microchannels. The results of simulations and accuracy/performance of the method are discussed. The developed approach can be used for solution of a wide range of problems related to emulsion flows in micro- and nanoscales.

scholarly journals 3D radiative transfer modelling of the dusty tori around active galactic nuclei as a clumpy two-phase medium

2012 ◽  
Vol 420 (4) ◽  
pp. 2756-2772 ◽  
Author(s):  
Marko Stalevski ◽  
Jacopo Fritz ◽  
Maarten Baes ◽  
Theodoros Nakos ◽  
Luka Č. Popović
Keyword(s):  
Radiative Transfer ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Two Phase ◽  
Phase Medium ◽  
Transfer Modelling

Elastic strain energy and forces on point defects in a two-phase medium

1986 ◽  
Vol 1 (1) ◽  
pp. 193-201 ◽  
Author(s):  
K. Jagannadham ◽  
J. Narayan
Keyword(s):  
Point Source ◽  
Point Defects ◽  
Elastic Strain ◽  
Strain Energy ◽  
Three Dimensional ◽  
Elastic Strain Energy ◽  
Second Phase ◽  
Two Phase ◽  
Phase Medium ◽  
Important Field

Elastic strain energy and forces on point defects in a two-phase medium with a planar interface are analyzed employing the surface dislocation analysis developed earlier for three-dimensional distortions. The important field components, namely, the tractions and the displacements arising due to the point source at the interface, are determined. Furthermore, the field components at the interface are used to determine the elastic strain energy associated with the point source in the two-phase medium and the elastic force exerted by the second phase on the point defect. The significance of these results to the force acting on a vacancy or an interstitial at the interface is emphasized.

scholarly journals Self-organization in a driven dissipative plasma system

2009 ◽  
Vol 76 (1) ◽  
pp. 107-116 ◽  
Author(s):  
DASTGEER SHAIKH ◽  
B. DASGUPTA ◽  
Q. HU ◽  
G. P. ZANK
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Spectral Energy ◽  
Small Scale ◽  
Plasma System ◽  
Self Organized ◽  
Wide Range ◽  
Characteristic Modes ◽  
Perpendicular Component ◽  
Migration Of Energy

AbstractWe perform a fully self-consistent three-dimensional numerical simulation for a compressible, dissipative magnetoplasma driven by large-scale perturbations, that contain a fairly broad spectrum of characteristic modes, ranging from largest scales to intermediate scales and down to the smallest scales, where the energy of the system is dissipated by collisional (ohmic) and viscous dissipations. Additionally, our simulation includes nonlinear interactions amongst a wide range of fluctuations that are initialized with random spectral amplitudes, leading to the cascade of spectral energy in the inertial range spectrum, and takes into account large-scale as well as small-scale perturbations that may have been induced by the background plasma fluctuations, as well as the non-adiabatic exchange of energy leading to the migration of energy from the energy-containing modes or randomly injected energy driven by perturbations and further dissipated by the smaller scales. Besides demonstrating the comparative decays of the total energy and the dissipation rate of the energy, our results show the existence of a perpendicular component of the current, thus clearly confirming that the self-organized state is non-force free.

SOME BOUNDS ON THE BULK CONDUCTIVITY OF A TWO-PHASE MEDIUM: A COMPARISON BETWEEN PERIODIC AND RANDOM STRUCTURE

1992 ◽  
Vol 02 (03) ◽  
pp. 283-294 ◽  
Author(s):  
ANDREA GAVIOLI
Keyword(s):  
Positive Constant ◽  
Percolation Theory ◽  
Effective Conductivity ◽  
Three Dimensional ◽  
Random Structure ◽  
Bulk Conductivity ◽  
Two Phase ◽  
Phase Medium

We prove that the effective conductivity of a three-dimensional medium with a periodic chessboard structure does not exceed [Formula: see text] where α and β are the values of the conductivity in the cells of the chessboard, and A is a positive constant; then we show how the corresponding “random” structure behaves in a quite different way, according to recent results in percolation theory.

scholarly journals Supersonic flow of two-phase gas- droplet flows in nozzles

2019 ◽  
Vol 21 (3) ◽  
pp. 86-98
Author(s):  
A. I. Sharapov ◽  
A. A. Chernykh ◽  
A. V. Peshkova
Keyword(s):  
Liquid Mixtures ◽  
Rocket Engines ◽  
Two Phase ◽  
Acoustic Effect ◽  
Practical Applications ◽  
Wide Range ◽  
Phase Medium ◽  
Integral Energy ◽  
Energy Equations ◽  
Droplet Flows

For practical applications, the description of processes occurring during the flow of two-phase gas-liquid mixtures requires a simple physical and mathematical model that describes the behavior of a two-phase medium in the entire range of phase concentrations changes and in a wide range of pressure changes. Problems of this kind arise in various branches of industry and technology. In the space industry, one often has to deal with the movement of various gases in rocket nozzles, consider the combustion, condensation of various vapors on the nozzle walls and their further impact on the velocity sublayer at the nozzle wall. The large acoustic effect arising from the engines affects the gas-liquid mixture in the nozzles of rocket engines. In the metal industry, metal cooling occurs with the help of nozzles in which the emulsion mixture is supplied under high overpressure. But this is only a short list of applied issues in which one has to deal with a problem of this type. The paper presents the results and directions of study of the problems of two-phase dispersed gas-droplet flows in the nozzles. The main methods of investigation of two- phase heterogeneous flows are described. The main characteristics of heterogeneous two-phase flows in the nozzles, which were confirmed by experimental results, are presented. The calculation of the air-droplet flow in the Laval nozzle is given. The technique, which is based on integral energy equations for two-phase dispersed flows, is described. The main problems and questions concerning the further description and studying of two-component flows are stated.

scholarly journals Influence of Bubble Deformation on the Signal Characteristics Generated Using an Optical Fiber Gas–Liquid Two-Phase Flow Sensor

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7338
Author(s):  
Yu Ma ◽  
Yangrui Zhang ◽  
Song Li ◽  
Weimin Sun ◽  
Elfed Lewis
Keyword(s):  
Optical Fiber ◽  
Chemical Engineering ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Measurements ◽  
Fiber Probe ◽  
Bubble Deformation ◽  
Wide Range

The use of optical fiber probe in two-phase flow measurements is very frequently encountered, especially in the applications of chemical engineering and petroleum industries. In this work, the influence of bubble piercing signals caused by bubble deformation is studied experimentally using a laboratory-prepared wedge-shaped fiber probe in a lab-scale gas–liquid flow generator. A three-dimensional simulation model is established to study the influence of bubble deformation on the piercing signals. A theoretical analysis of the characteristics of the pre-signal influenced by the bubble deformations is undertaken for a wide range of different modeled bubble shapes. Combining the experimental and simulation results, a promising analytical method to estimate the bubble shapes by analyzing the characteristics of pre-signals is proposed. The results of this investigation demonstrate that it is possible to estimate the bubble shapes before the fiber probe contacts the bubble surface. The method developed in this investigation is therefore highly promising for reducing errors caused by deformation during the probe piercing process.

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