scholarly journals Methane transport in a soil column: experimental and modeling investigation

2020 ◽  
Vol 26 (5) ◽  
pp. 200311-0
Author(s):  
Chiu-Shia Fen ◽  
Yu-Ro Lin ◽  
Chia-Yu Chen
Keyword(s):  
Density Profile ◽  
Soil Column ◽  
Transient State ◽  
Retardation Factor ◽  
Density Profiles ◽  
Horizontal Transport ◽  
Incomplete Mixing ◽  
Pure Methane ◽  
Methane Source ◽  
Upward Transport

This study explored two diffusion approaches, Fick’s law and the dusty gas model (DGM), to assess their differences on modeling methane transport in porous systems. Laboratory experiments were also conducted for methane transport through a nitrogen gas-dry soil column from different source densities. Gas pressures and methane densities at transient state were measured along the column for two transport configurations (horizontal and vertically upward) and compared with the predictions obtained from the DGM- and Fickian-based models. The retardation factor is the only parameter used in the model calibration. The results showed that the methane density profiles predicted by these models fairly matched the measured data and are quite consistent for vertically upward transport of methane. However, the predictions were over the measured ones for horizontal transport of methane. We suspected it is due to incomplete mixing of gas mixture in the inlet chamber since high pressure variations were observed in the horizontal transport experiments. Further, we found that the methane density profile predicted by the Fickian-based model is lagged behind the DGM result for at most 15% of difference in methane density for horizontal transport of methane from a pure methane source.horizontal transport experiments. Further, we found that the methane density profile predicted by the Fickian-based model lagged behind the DGM result for at most 15% of difference in methane density for horizontal transport of methane from a pure methane source.

scholarly journals A numerical fit of analytical to simulated density profiles in dark matter haloes

2005 ◽  
pp. 13-32 ◽  
Author(s):  
R. Caimmi ◽  
C. Marmo ◽  
T. Valentinuzzi
Keyword(s):  
High Resolution ◽  
Density Profile ◽  
Geometrical Parameters ◽  
Density Profiles ◽  
Mean Values ◽  
Geometrical Properties ◽  
Best Fitting ◽  
Definition Of ◽  
Additional Support ◽  
Open Question

Analytical and geometrical properties of generalized power-law (GPL) density profiles are investigated in detail. In particular, a one-to-one correspondence is found between mathematical parameters (a scaling radius, r0, a scaling density, ?0, and three exponents, ?, ?, ?), and geometrical parameters (the coordinates of the intersection of the asymptotes, xC, yC, and three vertical intercepts, b, b?, b?, related to the curve and the asymptotes, respectively): (r0,?0,?,?,?) ? (xC,yC,b,b?,b?). Then GPL density profiles are compared with simulated dark haloes (SDH) density profiles, and nonlinear least-absolute values and least-squares fits involving the above mentioned five parameters (RFSM5 method) are prescribed. More specifically, the sum of absolute values or squares of absolute logarithmic residuals, Ri=log?SDH(ri) ? log?GPL(ri), is evaluated on 10 points making a 5dimension hypergrid, through a few iterations. The size is progressively reduced around a fiducial minimum, and superpositions on nodes of earlier hypergrids are avoided. An application is made to a sample of 17 SDHs on the scale of cluster of galaxies, within a flat ?CDM cosmological model (Rasia et al. 2004). In dealing with the mean SDH density profile, a virial radius, Rvir, averaged over the whole sample, is assigned, which allows the calculation of the remaining parameters. Using a RFSM5 method provides a better fit with respect to other methods. The geometrical parameters, averaged over the whole sample of best fitting GPL density profiles, yield (?, ?, ?) ? (0.6,3.1,1.0), to be compared with (?, ?, ?) = (1,3,1), i.e. the NFW density profile (Navarro et al. 1995, 1996, 1997), (?, ?, ?) = (1.5,3, 1.5) (Moore et al. 1998, 1999), (?, ?, ?) = (1,2.5,1) (Rasia et al. 2004); and, in addition, ? ? 1.5 (Hiotelis 2003), deduced from the application of a RFSM5 method, but using a different definition of scaled radius, or concentration; and ? ? 1.21.3 deduced from more recent high-resolution simulations (Diemand et al. 2004, Reed et al. 2005). No evident correlation is found between SDH dynamical state (relaxed or merging) and asymptotic inner slope of the fitting logarithmic density profile or (for SDH comparable virial masses) scaled radius. Mean values and standard deviations of some parameters are calculated, and in particular the decimal logarithm of the scaled radius, ?vir, reads < log?vir >= 0.74 and ?slog?vir = 0.150.17, consistent with previous results related to NFW density profiles. It provides additional support to the idea, that NFW density profiles may be considered as a convenient way to parametrize SDH density profiles, without implying that it necessarily produces the best possible fit (Bullock et al. 2001). A certain degree of degeneracy is found in fitting GPL to SDH density profiles. If it is intrinsic to the RFSM5 method or it could be reduced by the next generation of high-resolution simulations, still remains an open question. .

Contact Value Formulae for the Density Profiles of the Electric Double Layer

2008 ◽  
Vol 73 (4) ◽  
pp. 558-574 ◽  
Author(s):  
Douglas J. Henderson ◽  
Lutful B. Bhuiyan
Keyword(s):  
Computer Simulations ◽  
Density Profile ◽  
Physical Interpretation ◽  
Electric Double Layer ◽  
Reasonable Agreement ◽  
Hard Wall ◽  
Density Profiles ◽  
Sum Rule ◽  
Recent Computer ◽  
Local Expression

An exact sum rule, due to Henderson, Blum, and Lebowitz, for the contact value of the density profile of ions in a primitive model electrolyte next to a planar, nonpolarizable charged hard wall, has been known for some years. This result has a pleasing physical interpretation and is local. It has been useful in assessing the accuracy of theoretical approximations. However, a sum rule for the contact value of the charge profile for the same system has, until recently, not been known. A few years ago, Boda and Henderson proposed what they thought might be a useful, but approximate, local expression for the contact value of the charge profile at a weakly charged electrode. Very recent computer simulations indicate that this expression may well be exact at low electrode charge. Recently, Holovko, Badiali, and di Caprio have obtained a more general, but nonlocal, sum rule for the contact value of the charge profile that is valid for all electrode charge. In this paper, we develop an alternative, nonlocal, but nonrigorous expression for this quantity. Both the expression of Holovko et al. and our new expression are examined by means of computer simulations. The Holovko et al. expression is exact and, within numerical uncertainties, seems supported by our simulations. Although admittedly nonrigorous, our simpler expression is in seemingly reasonable agreement with simulation and thus appears to be useful. The relation between the two expressions has not been established.

scholarly journals Determination of transport parameters for heavy metal in residual compacted soil using two methodologies

2006 ◽  
Vol 33 (7) ◽  
pp. 912-917
Author(s):  
Izabel Christina Duarte Azevedo ◽  
Cleidimar Rejane Nascentes ◽  
Antonio Teixeira de Matos ◽  
Roberto Francisco de Azevedo
Keyword(s):  
Heavy Metals ◽  
Dispersion Coefficient ◽  
Soil Column ◽  
Optimization Procedure ◽  
Retardation Factor ◽  
Hydrodynamic Dispersion ◽  
Column Test ◽  
Transport Parameters ◽  
Compacted Soil ◽  
Cumulative Mass

Values of the hydrodynamic dispersion coefficient and retardation factor obtained using the traditional and cumulative mass methods of column test analysis for zinc, manganese, and cadmium in a compacted soil are compared. The soil under study is from the B horizon of a residual gneissic tropical soil used for construction of the liner for the sanitary landfill in the District of Visconde do Rio Branco, Minas Gerais (MG), Brazil. To evaluate the behavior of landfill leachate heavy metals through the soil, soil column tests were performed on samples of compacted soil. A computational program that uses an optimization procedure to generate values of the hydrodynamic dispersion coefficient and retardation factor was developed to facilitate interpretation of the results obtained by the cumulative mass method. Values of the retardation factor and hydrodynamic dispersion coefficient were not influenced by the method of determination, even when a reduced number of effluent samples was used by the cumulative mass method. The use of the cumulative mass method, based on a reduced number of pore volumes, reduces the time and cost involved in the tests.Key words: heavy metals, column test, cumulative mass method.

Non-linear effects in a Rayleigh–Bénard experiment

1970 ◽  
Vol 42 (1) ◽  
pp. 161-175 ◽  
Author(s):  
D. R. Caldwell
Keyword(s):  
Rayleigh Number ◽  
Heat Flow ◽  
Density Profile ◽  
Critical Rayleigh Number ◽  
Temperature Drop ◽  
Density Profiles ◽  
Heating Curve ◽  
Linear Effects ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Observations of temperature drop as a function of heat flow in Rayleigh–Bénard convection with curved density profiles show: (1) reversal of slope in the heating curve, (2) oscillations with time, (3) history dependence, and (4) an increase in critical Rayleigh number as the curvature of the density profile is increased. Some of the results are quite similar to the predictions of Busse.

Study of C60 transport in porous media and the effect of sorbed C60 on naphthalene transport

2005 ◽  
Vol 20 (12) ◽  
pp. 3244-3254 ◽  
Author(s):  
Xuekun Cheng ◽  
Amy T. Kan ◽  
Mason B. Tomson
Keyword(s):  
Organic Carbon ◽  
Flow Velocity ◽  
Soil Column ◽  
Low Flow ◽  
Retardation Factor ◽  
Flow Rates ◽  
Limited Mobility ◽  
Flow Interruption ◽  
Breakthrough Experiments ◽  
First Time

In this study, the transport of water-stable “nano-C60 particles” (a term used to refer to underivatized C60 crystalline nanoparticles, stable in water for months) through a soil column (packed with Lula soil, 0.27% organic carbon) was investigated for the first time. Nano-C60 particle breakthrough experiments were conducted at different flow rates, while other column operating parameters remained fixed through all the experiments. Nano-C60 particles were observed to be more mobile at higher flow velocity: at the flow velocity of 0.38 m/d, the maximum percent of nano-C60 breakthrough (C/C0) was 47%; at the flow velocity of 3.8 m/d, the plateau value of nano-C60 breakthrough was 60%; and at the flow velocity of 11.4 m/d, the plateau value of nano-C60 breakthrough was almost 80%. At the low flow velocity (0.38 m/d), which is typical of groundwater flow, nano-C60 particles showed very limited mobility: after about 57 pore volumes, they deposited to the soil column so rapidly that virtually no nano-C60 was detected in the effluent. This observed “favorable deposition” (attachment efficiency α = 1) was probably due to “filter ripening.” Also the release of nano-C60 particles after flow interruption was observed. The transport of naphthalene through the same soil column containing 0.18% nano-C60 particles deposited was measured. A retardation factor of about 13 was observed, possibly suggesting that sorbed nano-C60 particles in the soil column sorbed naphthalene similar to soil organic carbon. An asymmetric naphthalene breakthrough curve was observed, which is possibly due to “sorption nonequilibrium.”

Determination of Technetium and Selenium Transport Properties in Laboratory Soil Columns

1988 ◽  
Vol 127 ◽  
Author(s):  
J. A. Del Debbio ◽  
T. R. Thomas
Keyword(s):  
Transport Properties ◽  
Soil Column ◽  
Retardation Factor ◽  
Soil Columns ◽  
Water Contact ◽  
Near Surface ◽  
One Dimensional ◽  
High Level ◽  
Water Saturated

ABSTRACTLaboratory studies are being conducted to measure the transport properties of various radionuclide species through soil columns. The studies are being conducted to support evaluations for potential near-surface disposal of high-level radioactive waste (HLW) calcine stored at the Idaho National Engineering Laboratory. The data will be used to model radionuclide transport through the vadose (unsaturated) zone of the site under various water-contact scenarios. Retardation factors and dispersion coefficients for technetium and selenium species have been measured in water-saturated soil columns made up of sediments taken from 12 and 35 meters below the surface. A one-dimensional, convective-dispersive, solute-transport equation was fitted to column effluent data by optimizing three parameters (retardation factor, dispersion coefficient and pulse time) using a non-linear, least-squares fitting routine. The data indicated no retardation of the pertechnetate ion (TcO4-)and selenate ion (SeO4-) and a large retardation of the selenite ion (SeO3-) relative to water transport through the soil column.

Time-dependent density profiles in a filling box

1983 ◽  
Vol 132 ◽  
pp. 457-466 ◽  
Author(s):  
M. Grae Worster ◽  
Herbert E. Huppert
Keyword(s):  
Numerical Integration ◽  
Density Profile ◽  
Approximate Expression ◽  
Time Dependent ◽  
Buoyant Plume ◽  
Governing Equations ◽  
Density Profiles ◽  
Approximate Analytic Expression ◽  
Analytic Expression ◽  
Dependent Density

An approximate analytic expression for the time-dependent density profile formed by a turbulent buoyant plume in a confined region is presented. The analysis is based on the approximation that the density of the fluid behind the first front changes at a rate which is virtually independent of position. The approximate expression is shown to be in excellent agreement with a full numerical integration of the governing equations.

scholarly journals On the universality of void density profiles

2014 ◽  
Vol 11 (S308) ◽  
pp. 551-554
Author(s):  
E. Ricciardelli ◽  
V. Quilis ◽  
J. Varela
Keyword(s):  
Dark Energy ◽  
Internal Structure ◽  
Density Profile ◽  
Matter Distribution ◽  
Density Profiles ◽  
Massive Galaxies ◽  
The Galaxy ◽  
Galaxy Sample ◽  
Low Mass ◽  
Void Radius

AbstractThe massive exploitation of cosmic voids for precision cosmology in the upcoming dark energy experiments, requires a robust understanding of their internal structure, particularly of their density profile. We show that the void density profile is insensitive to the void radius both in a catalogue of observed voids and in voids from a large cosmological simulation. However, the observed and simulated voids display remarkably different profile shapes, with the former having much steeper profiles than the latter. We ascribe such difference to the dependence of the observed profiles on the galaxy sample used to trace the matter distribution. Samples including low-mass galaxies lead to shallower profiles with respect to the samples where only massive galaxies are used, as faint galaxies live closer to the void centre. We argue that galaxies are biased tracers when used to probe the matter distribution within voids.

The impact of inverted density gradients on density profiles measured by reflectometry: an experimental and numerical investigation at ASDEX Upgrade

2022 ◽  
Vol 17 (01) ◽  
pp. C01008
Author(s):  
D. Hachmeister ◽  
C. Silva ◽  
J. Santos ◽  
G.D. Conway ◽  
L. Gil ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Density Profile ◽  
High Field ◽  
Continuous Wave ◽  
Dense Plasma ◽  
Density Profiles ◽  
Full Wave ◽  
Simulation And Experiment ◽  
Profile Reconstruction ◽  
The Impact

Abstract The high-field side high-density (HFSHD) region at ASDEX Upgrade (AUG) is a well-documented phenomenon leading to a dense plasma in the inner divertor region that expands upwards to the midplane, resulting in poloidally asymmetric scrape-off layer density profiles. This work investigates, via simulation and experiment, whether the HFSHD at the midplane leads to hollow density profiles at the high-field side. Using the frequency-modulated continuous-wave O-mode reflectometer at AUG, experimental evidence has been found of reflection patterns compatible with a hollow density profile that are reproduced by 1D full-wave simulations. Furthermore, this work assesses the uncertainties in the density profile reconstruction as a consequence of the inverted gradient, showing that the presence of an HFSHD may lead to an overestimation of the density in the confined region.

scholarly journals Techniques for measuring high-resolution firn density profiles: case study from Kongsvegen, Svalbard

2008 ◽  
Vol 54 (186) ◽  
pp. 463-468 ◽  
Author(s):  
Robert L. Hawley ◽  
Ola Brandt ◽  
Elizabeth M. Morris ◽  
Jack Kohler ◽  
Andrew P. Shepherd ◽  
...  
Keyword(s):  
High Resolution ◽  
Electrical Properties ◽  
Density Profile ◽  
Large Scale ◽  
Ice Core ◽  
Fine Scale ◽  
Density Profiles ◽  
The Core ◽  
Core Section

AbstractOn an 11 m firn/ice core from Kongsvegen, Svalbard, we have used dielectric profiling (DEP) to measure electrical properties, and digital photography to measure a core optical stratigraphy (COS) profile. We also used a neutron-scattering probe (NP) to measure a density profile in the borehole from which the core was extracted. The NP- and DEP-derived density profiles were similar, showing large-scale (>30 cm) variation in the gravimetric densities of each core section. Fine-scale features (<10 cm) are well characterized by the COS record and are seen at a slightly lower resolution in both the DEP and NP records, which show increasing smoothing. A combination of the density accuracy of NP and the spatial resolution of COS provides a useful method of evaluating the shallow-density profile of a glacier, improving paleoclimate interpretation, mass-balance measurement and interpretation of radar returns.

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