scholarly journals Understanding how porosity gradients can make a better filter using homogenization theory

2015 ◽  
Vol 471 (2182) ◽  
pp. 20150464 ◽  
Author(s):  
M. P. Dalwadi ◽  
I. M. Griffiths ◽  
M. Bruna
Keyword(s):  
Solute Transport ◽  
Homogenization Theory ◽  
Contaminant Removal ◽  
Computationally Efficient ◽  
Filter Efficiency ◽  
Second Stage ◽  
Advection Diffusion ◽  
Periodic Microstructure ◽  
Flow Through ◽  
Total Adsorption

Filters whose porosity decreases with depth are often more efficient at removing solute from a fluid than filters with a uniform porosity. We investigate this phenomenon via an extension of homogenization theory that accounts for a macroscale variation in microstructure. In the first stage of the paper, we homogenize the problems of flow through a filter with a near-periodic microstructure and of solute transport owing to advection, diffusion and filter adsorption. In the second stage, we use the computationally efficient homogenized equations to investigate and quantify why porosity gradients can improve filter efficiency. We find that a porosity gradient has a much larger effect on the uniformity of adsorption than it does on the total adsorption. This allows us to understand how a decreasing porosity can lead to a greater filter efficiency, by lowering the risk of localized blocking while maintaining the rate of total contaminant removal.

scholarly journals A multiscale method to calculate filter blockage

2016 ◽  
Vol 809 ◽  
pp. 264-289 ◽  
Author(s):  
M. P. Dalwadi ◽  
M. Bruna ◽  
I. M. Griffiths
Keyword(s):  
Homogenization Theory ◽  
Initial Porosity ◽  
Structure Evolution ◽  
Contaminant Removal ◽  
Unidirectional Flow ◽  
Average Porosity ◽  
Flow Through ◽  
As Adsorption ◽  
Asymptotic Reduction ◽  
Spatially Varying

Filters that act by adsorbing contaminant onto their pore walls will experience a decrease in porosity over time, and may eventually block. As adsorption will generally be greater towards the entrance of a filter, where the concentration of contaminant particles is higher, these effects can also result in a spatially varying porosity. We investigate this dynamic process using an extension of homogenization theory that accounts for a macroscale variation in microstructure. We formulate and homogenize the coupled problems of flow through a filter with a near-periodic time-dependent microstructure, solute transport due to advection, diffusion and filter adsorption, and filter structure evolution due to the adsorption of contaminant. We use the homogenized equations to investigate how the contaminant removal and filter lifespan depend on the initial porosity distribution for a unidirectional flow. We confirm a conjecture made by Dalwadi et al. (Proc. R. Soc. Lond. A, vol. 471 (2182), 2015, 20150464) that filters with an initially negative porosity gradient have a longer lifespan and remove more contaminant than filters with an initially constant porosity, or worse, an initially positive porosity gradient. In addition, we determine which initial porosity distributions result in a filter that will block everywhere at once by exploiting an asymptotic reduction of the homogenized equations. We show that these filters remove more contaminant than other filters with the same initial average porosity, but that filters which block everywhere at once are limited by how large their initial average porosity can be.

scholarly journals A Robust Flow-Through Platform for Organic Contaminant Removal

2021 ◽  
Vol 2 (1) ◽  
pp. 100296
Author(s):  
Long Chen ◽  
Akram N. Alshawabkeh ◽  
Shayan Hojabri ◽  
Meng Sun ◽  
Guiyin Xu ◽  
...  
Keyword(s):  
Organic Contaminant ◽  
Contaminant Removal ◽  
Flow Through

scholarly journals Modified boundary integral method for pressure driven MHD duct flow

1989 ◽  
Vol 12 (1) ◽  
pp. 159-174
Author(s):  
B. D. Aggarwala ◽  
P. D. Ariel
Keyword(s):  
Magnetic Field ◽  
Integral Method ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Duct Flow ◽  
Rectangular Duct ◽  
Computationally Efficient ◽  
Electrically Conducting ◽  
Flow Through ◽  
The Magnetic Field

In this paper, we investigate the flow of a viscous, Incompressible, electrically conducting fluid through a rectangular duct in the presence of a magnetic field, when one of the boundaries perpedicular to the magnetic field is partly conducting and partly Insulating, by a modified Boundary Integral Method.Three problems are considered (i) flow through an infinite channel, (ii) flow through a rectangular duct when the conducting part is symmetrically situated, and (iii) flow through a rectangular duct when the conducting part is arbltrarily positioned.Such problems have been studied before by asymptotic means for large values of M, the Hartmann number. Hoverer, the present modification of the Boundary Integral Method renders the problem computationally efficient and provides a reliable numerical solution for all values of M. For large M, our coputation time decreases significantly.

scholarly journals Assessing lateral flows and solute transport during floods in a conduit-flow-dominated karst system using the inverse problem for the advection–diffusion equation

2017 ◽  
Vol 21 (7) ◽  
pp. 3635-3653 ◽  
Author(s):  
Cybèle Cholet ◽  
Jean-Baptiste Charlier ◽  
Roger Moussa ◽  
Marc Steinmann ◽  
Sophie Denimal
Keyword(s):  
Inverse Problem ◽  
Solute Transport ◽  
Unsaturated Zone ◽  
Flood Routing ◽  
Saturated Zone ◽  
Karst System ◽  
Advection Diffusion Equation ◽  
Advection Diffusion ◽  
Karst Conduit ◽  
Conduit Network

Abstract. The aim of this study is to present a framework that provides new ways to characterize the spatio-temporal variability of lateral exchanges for water flow and solute transport in a karst conduit network during flood events, treating both the diffusive wave equation and the advection–diffusion equation with the same mathematical approach, assuming uniform lateral flow and solute transport. A solution to the inverse problem for the advection–diffusion equations is then applied to data from two successive gauging stations to simulate flows and solute exchange dynamics after recharge. The study site is the karst conduit network of the Fourbanne aquifer in the French Jura Mountains, which includes two reaches characterizing the network from sinkhole to cave stream to the spring. The model is applied, after separation of the base from the flood components, on discharge and total dissolved solids (TDSs) in order to assess lateral flows and solute concentrations and compare them to help identify water origin. The results showed various lateral contributions in space – between the two reaches located in the unsaturated zone (R1), and in the zone that is both unsaturated and saturated (R2) – as well as in time, according to hydrological conditions. Globally, the two reaches show a distinct response to flood routing, with important lateral inflows on R1 and large outflows on R2. By combining these results with solute exchanges and the analysis of flood routing parameters distribution, we showed that lateral inflows on R1 are the addition of diffuse infiltration (observed whatever the hydrological conditions) and localized infiltration in the secondary conduit network (tributaries) in the unsaturated zone, except in extreme dry periods. On R2, despite inflows on the base component, lateral outflows are observed during floods. This pattern was attributed to the concept of reversal flows of conduit–matrix exchanges, inducing a complex water mixing effect in the saturated zone. From our results we build the functional scheme of the karst system. It demonstrates the impact of the saturated zone on matrix–conduit exchanges in this shallow phreatic aquifer and highlights the important role of the unsaturated zone on storage and transfer functions of the system.

The prediction of solute transport in surcharged manholes using CFD

2007 ◽  
Vol 55 (4) ◽  
pp. 57-64 ◽  
Author(s):  
S.D. Lau ◽  
V.R. Stovin ◽  
I. Guymer
Keyword(s):  
Solute Transport ◽  
Laboratory Data ◽  
Transport Processes ◽  
Relevant Parameter ◽  
Computationally Efficient ◽  
Engineering Structures ◽  
Advection Dispersion ◽  
Hydraulic Regime ◽  
Wide Range ◽  
Discrete Phase

Solute transport processes occur within a wide range of water engineering structures, and urban drainage engineers increasingly rely on modelling tools to represent the transport of dissolved materials. The models take as input representative travel time and dispersion characteristics for key system components, and these generally have to be identified via field or laboratory measurements. Computational Fluid Dynamics (CFD) has the potential to reveal the underlying hydraulic processes that control solute transport, and to provide a generic means of identifying relevant parameter values. This paper reports on a study that has been undertaken to evaluate the feasibility of utilising a CFD-based approach to modelling solute transport. Discrete phase modelling has been adopted, as this is computationally efficient and robust when compared with the time-dependent solution of the advection–dispersion equation. Simulation results are compared with published laboratory data characterising the dispersion effects of surcharged manholes, focusing specifically on an 800 mm diameter laboratory manhole for a flowrate of 0.002 m3/s and a range of surcharge depths. Preliminary indications are that the CFD results adequately replicate the measured downstream temporal concentration profiles, and that a threshold surcharge depth, corresponding to a change in hydraulic regime within the manhole, can also be identified.

Studies on the impact of external fire on the lye of the shelter housing

2021 ◽  
Vol 109 (1) ◽  
pp. 11-16
Author(s):  
A. Baryłka
Keyword(s):  
Numerical Analysis ◽  
Second Stage ◽  
Heating And Cooling ◽  
Flow Through ◽  
Time Changes ◽  
Two Stages ◽  
The Impact ◽  
Fourier Equation ◽  
Practical Implications ◽  
Vast Area

Purpose: The presented article presents a numerical analysis carried out to determine the impact of an external fire taking place on the surface of the ground on the level of stress of the trench shelter casing protected by a layer of soil. Design/methodology/approach: Numerical analysis was carried out in two stages. In the first stage, a quasi-stationary distribution of the initial temperature in the centre of the ground and the shelter casing was sought. In the second stage of the analysis, the effect of the fire was considered according to the profile of time changes in the temperature of the shelter object. Findings: We assume that the trench shelter is in an oblong shape, and the fire extends over a vast area. The area surrounding the shelter casing was treated as a material with average constant thermodynamic values. Research limitations/implications: The process related to heating and cooling the enclosure was described on the basis of the Fourier equation on heat conduction in terms of the heterogeneous nature of the material, primer and concrete. Practical implications: The use of the trench shelter model as a research element in the design of special objects. Originality/value: The methods of non-stationary temperature flow through the ground and the shelter casing used, allows for a very realistic indication of how the housing will behave under the influence of high temperature caused by an external fire. The article can be useful for designers who design underground shelters.

Development of a Swirl Nozzle for Powder Technology

2013 ◽  
Author(s):  
Mehmet Alper Sofuoglu ◽  
Murat Erbas ◽  
Ibrahim Uslan ◽  
Atilla Biyikoglu
Keyword(s):  
Lower Cost ◽  
Nozzle Geometry ◽  
Design Parameters ◽  
Maximum Pressure ◽  
Pressure Data ◽  
Delivery Tube ◽  
Second Stage ◽  
Flow Through ◽  
Two Stages ◽  
Atomization Nozzle

In this study, a gas atomization nozzle for metal powder production has been designed and modeled numerically. The design has been performed in two stages. At the first stage of the design, the size and geometry of the nozzle have been developed to obtain circulated flow through the nozzle as a pre-design. At the second stage, a parametrical analysis has been done using a CFD code. The geometry of the nozzle has been changed and the effect of geometric parameters was determined to find out the more efficient nozzle design parameters. Gas behavior at the nozzle exit and effect of the gas on the melt delivery tube tip has been investigated. Appropriate values for the investigated parameters have been determined to get maximum pressure in vacuum condition at the tip of the melt. The pressure observed at the melt delivery tube was compared with the experimental melt tip pressure data. These results suggest that the CFD solutions can be used in the design of the nozzle. Thus, the lower cost and shorter time would be possible to develop highly efficient nozzle geometry.

scholarly journals Toward a continuum model for particle-induced velocity fluctuations in suspension flow through a stenosed geometry

2014 ◽  
Vol 25 (12) ◽  
pp. 1441013 ◽  
Author(s):  
Florian Janoschek ◽  
Jens Harting ◽  
Federico Toschi
Keyword(s):  
Lattice Boltzmann ◽  
Coarse Grained ◽  
Parallel Plates ◽  
Computationally Efficient ◽  
Suspension Flows ◽  
Velocity Fluctuations ◽  
Benchmark System ◽  
Flow Through ◽  
Induced Velocity ◽  
Macroscopic Continuum

Nonparticulate continuum descriptions allow for computationally efficient modeling of suspension flows at scales that are inaccessible to more detailed particulate approaches. It is well known that the presence of particles influences the effective viscosity of a suspension and that this effect has thus to be accounted for in macroscopic continuum models. The present paper aims at developing a nonparticulate model that reproduces not only the rheology but also the cell-induced velocity fluctuations, responsible for enhanced diffusivity. The results are obtained from a coarse-grained blood model based on the lattice Boltzmann (LB) method. The benchmark system comprises a flow between two parallel plates with one of them featuring a smooth obstacle imitating a stenosis. Appropriate boundary conditions are developed for the particulate model to generate equilibrated cell configurations mimicking an infinite channel in front of the stenosis. The averaged flow field in the bulk of the channel can be described well by a nonparticulate simulation with a matched viscosity. We show that our proposed phenomenological model is capable to reproduce many features of the velocity fluctuations.

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