Micro-Scale Flow Simulations and Permeability Estimation of Cleat Networks in Coal

2016 ◽  
Vol 846 ◽  
pp. 42-47
Author(s):  
J. Busse ◽  
S. Galindo Torres ◽  
Alexander Scheuermann ◽  
L. Li ◽  
D. Bringemeier
Keyword(s):  
Gas Flow ◽  
Structural Information ◽  
Porous Matrix ◽  
Groundwater Levels ◽  
Micro Scale ◽  
Wide Range ◽  
Boltzmann Method ◽  
The Impact ◽  
Flow Experiments

Coal mining raises a number of environmental and operational challenges, including the impact of changing groundwater levels and flow patterns on adjacent aquifer and surface water systems. Therefore it is of paramount importance to fully understand the flow of water and gases in the geological system on all scales. Flow in coal seams takes place on a wide range of scales from large faults and fractures to the micro-structure of a porous matrix intersected by a characteristic cleat network. On the micro-scale these cleats provide the principal source of permeability for fluid and gas flow. Description of the behaviour of the flow within the network is challenging due to the variations in number, sizing, orientation, aperture and connectivity at a given site. This paper presents a methodology to simulate flow and investigate the permeability of fractured media. A profound characterization of the geometry of the cleat network in micrometer resolution can be derived by CT-scans. The structural information is fed into a Lattice Boltzmann Method (LBM) based model that allows the implementation of virtual flow experiments. With the application of suitable hydraulic boundary conditions the full permeability tensor can be calculated in 3D.

scholarly journals Development of FTIR Spectroscopy Methodology for Characterization of Boron Species in FCC Catalysts

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1327 ◽  
Author(s):  
Claire Chunjuan Zhang ◽  
Xingtao Gao ◽  
Bilge Yilmaz
Keyword(s):  
Structural Information ◽  
Glass Ceramics ◽  
Boron Trioxide ◽  
Fcc Catalyst ◽  
Ftir Characterization ◽  
Wide Range ◽  
The World ◽  
Contaminant Metals ◽  
Fcc Catalysts

Fluid Catalytic Cracking (FCC) has maintained its crucial role in refining decades after its initial introduction owing to the flexibility it has as a process as well as the developments in its key enabler, the FCC catalyst. Boron-based technology (BBT) for passivation of contaminant metals in FCC catalysts represents one such development. In this contribution we describe Fourier Transform Infrared Spectroscopy (FTIR) characterization of boron-containing catalysts to identify the phase and structural information of boron. We demonstrate that FTIR can serve as a sensitive method to differentiate boron trioxide and borate structures with a detection limit at the 1000 ppm level. The FTIR analysis validates that the boron in the FCC catalysts studied are in the form of small borate units and confirms that the final FCC catalyst product contains no detectable isolated boron trioxide phase. Since boron trioxide is regulated in some parts of the world, this novel FTIR methodology can be highly beneficial for further FCC catalyst development and its industrial application at refineries around the world. This new method can also be applied on systems beyond catalysts, since the characterization of boron-containing materials is needed for a wide range of other applications in the fields of glass, ceramics, semiconductors, agriculture, and pharmaceuticals.

scholarly journals Review on the Impact of Polyols on the Properties of Bio-Based Polyesters

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2969
Author(s):  
Kening Lang ◽  
Regina J. Sánchez-Leija ◽  
Richard A. Gross ◽  
Robert J. Linhardt
Keyword(s):  
Tissue Engineering ◽  
Biomedical Applications ◽  
Molecular Level ◽  
Potential Utility ◽  
Reaction Conditions ◽  
Wide Range ◽  
Soft Tissue Engineering ◽  
The Impact ◽  
Optimal Reaction

Bio-based polyol polyesters are biodegradable elastomers having potential utility in soft tissue engineering. This class of polymers can serve a wide range of biomedical applications. Materials based on these polymers are inherently susceptible to degradation during the period of implantation. Factors that influence the physicochemical properties of polyol polyesters might be useful in achieving a balance between durability and biodegradability. The characterization of these polyol polyesters, together with recent comparative studies involving creative synthesis, mechanical testing, and degradation, have revealed many of their molecular-level differences. The impact of the polyol component on the properties of these bio-based polyesters and the optimal reaction conditions for their synthesis are only now beginning to be resolved. This review describes our current understanding of polyol polyester structural properties as well as a discussion of the more commonly used polyol monomers.

Study on Dynamic Behavior of a Gas Pressure Relief Valve for a Big Flow Rate

2013 ◽  
Author(s):  
Victor Sverbilov ◽  
Dmitry Stadnick ◽  
Georgy Makaryants
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Dynamic Properties ◽  
Gas Pressure ◽  
Pressure Relief Valve ◽  
Relief Valve ◽  
Pressure Relief ◽  
Wide Range ◽  
The Impact ◽  
Pilot Valve

The paper investigates instable behavior of a poppet-type gas pressure relief valve operating at a big flow rate (more than 2 kg/s) under super critical pressure drop. Instability is experienced as noise and vibration and leads to severe damage of a seat and other elements. Significant and unsteady flow forces coupled with small inherent damping make it difficult to stabilize the system. In previous works, the analytical and experimental research was carried out to reveal the most essential factors influencing stability and dynamic properties of the valve. The impact of the pilot valve dynamics on the system behavior was studied for the purpose of obtaining required accuracy and stability in a wide range of flow rate. It was shown in some testing that unstable behavior of the main valve occurred when the pilot valve was stable. This paper considers inherent stability of the main valve in the gas flow. CFD software ANSYS FLUENT is employed to study the effect of the poppet geometry on aerodynamic lifting force and valve stability in axial and lateral direction. The results have been verified through comparison with experimental data.

The fate of infiltrated stormwater from infiltration basins to the stream: quantifying the impact of the urban karst

2020 ◽  
Author(s):  
Abolfazl Poozan ◽  
ََAndrew Western ◽  
Meenakshi Arora ◽  
Matthew Burns ◽  
Tim Fletcher
Keyword(s):  
Short Circuit ◽  
Control Measures ◽  
Sewer Pipes ◽  
Groundwater Levels ◽  
Novel Approach ◽  
Wide Range ◽  
Underground Infrastructure ◽  
Receiving Waters ◽  
Stormwater Control Measures ◽  
The Impact

<p>Urbanization leads to severe alterations to the flow regime of receiving waters, including increased frequency and magnitude of storm flows as well as reduced baseflows. Infiltration basins are among the most widely applied stormwater control measures worldwide, in part for their ability to intercept stormwater runoff and allow it to infiltrate into the ground, with the assumption that this will recharge groundwater and thus help in restoring clean, filtered baseflows to receiving waters. Recent research has highlighted that in fact, the fate of infiltrated stormwater is highly uncertain, particularly because of likely interactions with underground infrastructure—e.g. sewer pipes, telecommunication cables, etc. These infrastructures are typically surrounded by highly permeable material which has the potential to substantially alter the way infiltrated stormwater moves through the subsurface (a phenomenon known as the urban karst).</p><p>This study aimed to predict and generalize the impact of the urban karst on infiltrated stormwater as it can provide a preferential flowpath and thus may prevent infiltrated stormwater from reaching receiving waters or may short circuit subsurface storages that can increase routing time delays and thus baseflow. In doing so, a modelling study using HYDRUS-3D was undertaken. In addition, a novel approach to generalize the results was proposed based on groundwater level and the hydraulic conductivities of soil and gravel/sand. We predicted that the impact of the urban karst on infiltrated stormwater increases whit higher groundwater levels, and greater contrasts between the hydraulic conductivity of regional soil and gravel. The HYDRUS results for a wide range of scenarios are compared with the generalization, which captures the impact of Urban Karst well.</p><p>It is important to consider the impact of the urban karst where one of the goals of building infiltration basins is to recharge the baseflow of the stream downslope. This suggests that decision on basin location is important where urban infrastructure is located between potential infiltration basin sites and downslope stream. The impact of the urban karst should be investigated at each specific site before implementing infiltration systems and this study works towards simplified representations of impact for design.</p>

Modelling biofilm-modified hydrodynamics in 3D

2007 ◽  
Vol 55 (8-9) ◽  
pp. 275-281 ◽  
Author(s):  
D.A. Graf von der Schulenburg ◽  
L.F. Gladden ◽  
M.L. Johns
Keyword(s):  
Packed Bed ◽  
Observation Time ◽  
Biofilm Growth ◽  
Transport Dynamics ◽  
Wide Range ◽  
Simulation Based ◽  
Flow Through ◽  
Three Stages ◽  
Boltzmann Method ◽  
The Impact

A simulation–based study to predict the impact of biofilm growth on displacement distributions for flow of water through a supporting packed bed is presented. The lattice Boltzmann method and a directed random walk algorithm are used, and are applied to the system with and without biofilm being present. The aim of this simulation study is to model the anomalous transport dynamics induced by biofilm, as reported in the literature, and thus to study the impact of observation time, Δ, on the shape of the displacement distributions (propagators). We believe that this is the first demonstration of a propagator simulation for flow through a complex porous structure modulated by biofilm growth. The propagator distributions undergo a transition from a pre-asymptotic to a Gaussian-shaped distribution with increasing Δ. The propagators were simulated for a wide range of Δ going up to 500 seconds. This transition occurs with and without biofilm, but is very significantly delayed when biofilm is present due to the consequential development of essentially stagnant regions. The transition can be classified into three stages: a diffusion-dominated stage, a “twin-peak” stage and an advection-dominated stage.

Microstructural Characterization of Photoluminescent Porous Silicon

1991 ◽  
Vol 256 ◽  
Author(s):  
J. M. Macaulay ◽  
F. M. Ross ◽  
P. C. Searson ◽  
S. K. Sputz ◽  
R. People ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Optical Properties ◽  
Porous Silicon ◽  
Microstructural Characterization ◽  
Photoluminescence Spectroscopy ◽  
Experimental Results ◽  
Visible Luminescence ◽  
Wide Range ◽  
The Impact

ABSTRACTWe have used electron microscopy to examine the microstructure of porous silicon films over a wide range of doping levels, and photoluminescence spectroscopy to study their optical properties. We discuss the impact of our experimental results on models from the literature which were proposed to explain visible luminescence from porous silicon.

Simulation of Gas Flow in Channels with Variable Cross-Section at Different Flow Modes using Lattice Boltzmann Method (LBM)

2019 ◽  
pp. 105-115
Author(s):  
A.V. Burmistrov ◽  
S.I. Salikeev ◽  
A.A. Raykov
Keyword(s):  
Lattice Boltzmann Method ◽  
Cross Section ◽  
Lattice Boltzmann ◽  
Gas Flow ◽  
Stokes Equations ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Wide Range ◽  
Boltzmann Method ◽  
Contact Free

All contact-free vacuum pumps operate in a very wide pressure range. Therefore, the calculation of flows through the slot channels is associated with the need to take into account the laws of all three modes of gas flow: viscous, transitional and molecular. Most of channels of contact-free pumps are formed by curved walls, which are slits of variable cross-section in the direction of gas flow, having a minimum gap in some place. The paper considers the basic methods of calculating flows in channels of variable cross-section: the Monte Carlo method for molecular mode, the numerical solution of Navier --- Stokes equations for viscous mode and the Lattice Boltzmann method (LBM) for a wide range of pressures. The results of gas flow simulation calculated in COMSOL Multiphysics with LBM method are presented. The influence of the gas flow mode on the velocity profile in the channel is discussed. Based on the simulation results, the conductivity of channels of different geometries was calculated at various pressures at the inlet and outlet of the channel. The graphs of conductivity dependence on the Knudsen number for the method of angular coefficients, the model of lattice Boltzmann equations and experimental data are presented. It is shown that for slit channels of variable cross-section, the LBM model agrees well with the experiment under any gas flow modes.

scholarly journals Experimental Characterization of the Jet Wiping Process

2018 ◽  
Vol 180 ◽  
pp. 02064
Author(s):  
Miguel Alfonso Mendez ◽  
Adriana Enache ◽  
Anne Gosset ◽  
Jean-Marie Buchlin
Keyword(s):  
Gas Flow ◽  
Detection Algorithm ◽  
Gas Flows ◽  
Experimental Characterization ◽  
Data Set ◽  
Time Resolved ◽  
Numerical Studies ◽  
Image Velocimetry ◽  
The Impact

This paper presents an experimental characterization of the jet wiping process, used in continuous coating applications to control the thickness of a liquid coat using an impinging gas jet. Time Resolved Particle Image Velocimetry (TR-PIV) is used to characterize the impinging gas flow, while an automatic interface detection algorithm is developed to track the liquid interface at the impact. The study of the flow interaction is combined with time resolved 3D thickness measurements of the liquid film remaining after the wiping, via Time Resolved Light Absorption (TR-LAbs). The simultaneous frequency analysis of liquid and gas flows allows to correlate their respective instability, provide an experimental data set for the validation of numerical studies and allows for formulating a working hypothesis on the origin of the coat non-uniformity encountered in many jet wiping processes.

scholarly journals Recent Advances in Camel Immunology

2021 ◽  
Vol 11 ◽  
Author(s):  
Jamal Hussen ◽  
Hans-Joachim Schuberth
Keyword(s):  
Cytotoxic T Cells ◽  
Functional Characterization ◽  
Desert Ecosystem ◽  
Physiological Age ◽  
Cellular Immunology ◽  
Wide Range ◽  
Innate Recognition ◽  
Antigen Presenting ◽  
The Impact

Camels are domesticated animals that are highly adapted to the extreme desert ecosystem with relatively higher resistance to a wide range of pathogens compared to many other species from the same geographical region. Recently, there has been increased interest in the field of camel immunology. As the progress in the analysis of camel immunoglobulins has previously been covered in many recent reviews, this review intends to summarize published findings related to camel cellular immunology with a focus on the phenotype and functionality of camel leukocyte subpopulations. The review also describes the impact of different physiological (age and pregnancy) and pathological (e.g. infection) conditions on camel immune cells. Despite the progress achieved in the field of camel immunology, there are gaps in our complete understanding of the camel immune system. Questions remain regarding innate recognition mechanisms, the functional characterization of antigen-presenting cells, and the characterization of camel NK and cytotoxic T cells.

Fluid-Dynamic Characterization of a CNG Injection System

2012 ◽  
Author(s):  
Mirko Baratta ◽  
Daniela Misul ◽  
Ezio Spessa ◽  
Giuseppe Gazzilli ◽  
Andrea Gerini
Keyword(s):  
Mass Flow ◽  
Fluid Dynamic ◽  
Injection System ◽  
Rail Pressure ◽  
Dynamic Characterization ◽  
Pressure Regulator ◽  
Fuel Mass ◽  
Wide Range ◽  
The Impact

A renewed interest in CNG fuelled engines, which has recently been boosted by the even more stringent emissions regulations, has generated considerable R&D activity in the last few years. In order to fulfill such limits, most current CNG vehicles combine advanced technical and control solutions such as VVA intake systems, new turbocharging solutions, enhanced ECU strategies, etc. The present work focuses on the complete fluid-dynamic characterization of a gaseous injection system so as to support the design of the related control module and devices. To that end, a numerical investigation into the fluid-dynamic behavior of a commercial CNG injection system has been extensively carried out by means of the GT-POWER code. A detailed geometrical model including the rail, the injectors as well as the pipe connecting the pressure regulator to the rail has been built in the GT-POWER environment. The model has been validated by comparing the experimental to the numerical outputs for the rail pressure and for the injected mass quantity. The model has hence been applied to the prediction of the pressure waves produced by the injection event and of their effect on the actually injected fuel mass. Moreover, the influence of the pressure regulator dynamics has been assessed by simulating the impact on the system behavior of a pressure noise downstream from the regulator. Finally, the possibility of reducing the rail volume, thus enhancing its dynamic response, has been investigated. The results have shown a good agreement between the predicted and the measured rail pressure and injected fuel mass flow rates over a wide range of engine operation conditions. Moreover, the dynamic simulations sketched a dependence of the injected fuel mass on the average rail pressure level, which in turn appeared to reduce for increasing engine power outputs. Finally, the reduction in the rail volume has proved not to significantly affect the injected mass flow rate.

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