Group Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Title: P3.19 - Experimentally Measured Interfacial Area during Gas Injection into Saturated Porous Media: An Air Sparging Analogy
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 Material Information
Title: P3.19 - Experimentally Measured Interfacial Area during Gas Injection into Saturated Porous Media: An Air Sparging Analogy Fluidized and Circulating Fluidized Beds
Series Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Physical Description: Conference Papers
Creator: Crandall, D.
Ahmadi, G.
Smith, D.H.
Bromhal, G.
Publisher: International Conference on Multiphase Flow (ICMF)
Publication Date: June 4, 2010
 Subjects
Subject: capillary fringe
stereolithography
variably saturated flow
 Notes
Abstract: The amount of interfacial area (awn) between air and subsurface liquids during air-sparging can limit the rate of site remediation. Lateral movement within porous media could be encountered during air-sparging operations when air moves along the bottom of a low-permeability lens. This study was conducted to directly measure the amount of awn between air and water flowing within a bench-scale porous flow cell during the lateral movement of air along the upper edge of the cell during air injections into an initially water-saturated flow cell. Four different cell orientations were used to evaluate the effect of air injection rates and porous media geometries on the amount of awn between fluids. Air was injected at flow rates that varied by three orders of magnitude, and for each flow cellover this range of injection rates little change in awn was noted. A wider variation in awn was observed when air moved through different regions for the different flow cell orientations. These results are in good agreement with the experimental findings of Waduge et al. (2007), who performed experiments in a larger sand-pack flow cell, and determined that air-sparging efficiency is nearly independent of flow rate but highly dependent on the porous structure. By directly measuring the awn, and showing that awn does not vary greatly with changes in injection rate, we show that the lack of improvement to remediation rates is because there is a weak dependence of the awn on the air injection rate.
General Note: The International Conference on Multiphase Flow (ICMF) first was held in Tsukuba, Japan in 1991 and the second ICMF took place in Kyoto, Japan in 1995. During this conference, it was decided to establish an International Governing Board which oversees the major aspects of the conference and makes decisions about future conference locations. Due to the great importance of the field, it was furthermore decided to hold the conference every three years successively in Asia including Australia, Europe including Africa, Russia and the Near East and America. Hence, ICMF 1998 was held in Lyon, France, ICMF 2001 in New Orleans, USA, ICMF 2004 in Yokohama, Japan, and ICMF 2007 in Leipzig, Germany. ICMF-2010 is devoted to all aspects of Multiphase Flow. Researchers from all over the world gathered in order to introduce their recent advances in the field and thereby promote the exchange of new ideas, results and techniques. The conference is a key event in Multiphase Flow and supports the advancement of science in this very important field. The major research topics relevant for the conference are as follows: Bio-Fluid Dynamics; Boiling; Bubbly Flows; Cavitation; Colloidal and Suspension Dynamics; Collision, Agglomeration and Breakup; Computational Techniques for Multiphase Flows; Droplet Flows; Environmental and Geophysical Flows; Experimental Methods for Multiphase Flows; Fluidized and Circulating Fluidized Beds; Fluid Structure Interactions; Granular Media; Industrial Applications; Instabilities; Interfacial Flows; Micro and Nano-Scale Multiphase Flows; Microgravity in Two-Phase Flow; Multiphase Flows with Heat and Mass Transfer; Non-Newtonian Multiphase Flows; Particle-Laden Flows; Particle, Bubble and Drop Dynamics; Reactive Multiphase Flows
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Resource Identifier: P319-Crandall-ICMF2010.pdf

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7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010


Paper No


means of improving the efficiency of an air sparging-soil
vapor extraction (AS-SVE) system is to increase the
amount of interfacial area between the injected air and the
in-place liquids, i.e. the interfacial area between wetting and
non-wetting fluids (awn). Previous experimental studies
have shown the importance of having as much air come into
contact with trapped contaminants as possible to facilitate
rapid cleanup in laboratory-scale porous media (Elder and
Benson, 1999; Reddy et al., 1999; Rogers and Ong, 2000;
Braida and Ong, 2000). When a greater amount of injected
air came into contact with contaminants, either by the


Experimentally Mleasured Interfacial Area during Gas Injection into Saturated Porous
Media: An Air Sparging Analogy


D. Crandall G. Ahmadi2, D.H. Smith, and G. Bromhal4

'URS Washington Division, National Energy Technology Laboratory

Morgantown, WV 26507 USA
Dustin. Crandall~iur. netl. doe. gov


M1Lechanical and Aeronautical Engineering Department, Clarkson University
Potsdam, NY 13699, USA

gahmadi~,clarkson~edu


3National Energy Technology Laboratory

Morgantown, WV 26507 USA
Duane. Smith anetl.doe.gov


4National Energy Technology Laboratory

Morgantown, WV 26507 USA
Grant.Bromhal~netl.doe.gov

Keywords: Capillary fringe, stereolithography, variably saturated flow




Abstract

The amount of interfacial area (awn) between air and subsudface liquids during air-sparging can limit the rate of site
remediation. Lateral movement within porous media could be encountered during air-sparging operations when air moves
along the bottom of a low-permeability lens. This study was conducted to directly measure the amount of ass, between air and
water flowing within a bench-scale porous flow cell during the lateral movement of air along the upper edge of the cell during
air injections into an initially water-saturated flow cell. Four different cell orientations were used to evaluate the effect of air
injection rates and porous media geometries on the amount of as, between fluids. Air was injected at flow rates that varied by
three orders of magnitude, and for each flow cellover this range of injection rates little change in awn was noted. A wider
variation in awn was observed when air moved through different regions for the different flow cell orientations. These results
are in good agreement with the experimental findings of Waduge et al. (2007), who performed experiments in a larger
sand-pack flow cell, and determined that air-sparging efficiency is nearly independent of flow rate but highly dependent on the
porous structure. By directly measuring the awn, and showing that awn does not vary greatly with changes in injection rate, we
show that the lack of improvement to remediation rates is because there is a weak dependence of the awn on the air injection
rate.


Introduction

Air sparging is a low-cost site-remediation procedure that
has been used to cleanup volatile organic compounds
(VOC) and other nonaqueous phase liquids (NAPL) from
contaminated subsurface regions. The vertical motion of the
low-density air through a polluted region carries VOC
and/or NAPL upwards into the vadose zone, where a soil
vapor extraction system can extract the pollutants. In
addition, bioremediation of certain contaminated sites is
possible with the injection of air (King et al., 1992). A












































~ E I


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

perfonned by Waduge et al. (2007). They showed that the
removal rate was almost independent of the air flow rate.
Differences in the remediation efficiency due to the lens
penneabilities were observed, with more toluene removed
from experiments that contained a coarse-sand lens. It was
hypothesized that the improved removal rate was directly
related to the amount of contact the air had with the
contaminants, i.e. the awn within the system.
The direct measurement of awn is not easily perfonned in
most laboratory-scale experiments of flow through porous
media. Two methods of obtaining the awn from experiments
are direct measurements via visual analysis and an
interfacial tracer technique (IFTT). The IFTT determines
the awn from the area of a monolayer of surfactant
molecules absorbed at the interface (Chen and Kibbey,
2006). By measuring the changes in surfactant saturation
during drainage cycles the IFTT has been used to obtain
measurements of the awn in bead packs as a function of the
P, and Sw (Chen and Kibbey, 2006). A study by Brusseau et
al. (2006) showed that the IFTT tends to measure a larger
awn than was observed by microtomography measurements.
This larger measurement by the IFTT was hypothesized to
be due to the inclusion of all the interfacial areas between
the fluids, including the thin wetting layers on the surface of
rough grains, which could not be resolved by the
computerized tomography (CT) scanner. A distinct
advantage of using the IFTT to measure the awn is that
complex porous media models can be used without the need
to reconstruct individual interfaces within intricate
geometries (Dalla et al. 2002).
A potential method of determining the awn was identified by
Powers et al. (1992), where blobs of NAPL were solidified
within different sand columns and subsequently removed.
Analysis revealed that the volumes of individual NAPL
blobs trapped within different grades of sand decreased
with decreasing grain size and increasing sand uniformity,
due to more single-pore NAPL trappings. When the NAPL
was separated into these smaller globules the overall awn
was greater and thus remediation within the uniform,
fine-grained sand packs was the most complete.
Measurement of the awn using micro-CT scanning has also
been perfonned within bead packs by Culligan et al. (2Ir1is14
and within soil Brusseau et al. (2006). Neither of these awn
measurement methods was particularly easy, requiring
either the solidification of specialty fluids within the porous
media or expensive imaging equipment. Our study differs
from these previously identified awn measurement methods
by using a fairly simple image capturing system and a
manufactured porous flow cell with known geometric
properties.
Since previous studies have shown that NAPL and VOC
spills tend to coalesce within and around low penneability
lenses (Conrad et al. 2002; Kechavarzi et al. 2008), and the
rate of remediation has been shown to be related to the
amount of contact the air has with the contaminates (Reddy
et al., 1999; Braida and Ong, 2000; Waduge et al. 2007),
our study was conducted to evaluate the change in awn due
to different injection rates that occur as air moves laterally
under a no-flow boundary in a porous medium. This
situation is meant to replicate the flow of fluids moving
laterally under a low-penneability lens. Our experiments to
measure the interfacial area were performed within a
fabricated flow cell (Crandall et al. 2008). Air was


Paper No


fonnation of flow channels (Elder and Benson, 1999;
Braida and Ong, 2000) or by inducing bubbling flows
(Reddy et al., 1999; Rogers and Ong, 2000), the
contaminants were removed faster.
Soil heterogeneities can dramatically affect the subsudface
motion of both injected air and NAPL/VOC spills.
Low-permeability lenses within a sand-filled chamber have
been shown by Conrad et al. (2002) to influence the
distribution of dense NAPL spills, with pooling occurring
around medium and fine-grade sand lenses. Similarly, a
study by Kechavarzi et al. (2008) showed that layered
regions of different penneability sands cause spilled NAPL
to pool in the top or bottom of low-penneability regions.
The tendency of contaminants to coalesce in and around
these low-penneability lenses indicates that knowledge of
potential removal rates adjacent to these regions will be of
importance in planning remediation operations. Air which is
injected below a low-penneability lens will travel laterally
along the bottom of the lens, rather than vertically, due to
the capillary resistance of the small-pores within the lens.
This potential situation is illustrated in Figure 1, where an
AS-SVE system is shown injecting air below a contaminant
plume and vapor extraction is occurring in the vadose zone.
Within the aquifer a lens of low-permeability media is
shown, which could readily cause both the injected air and
the contaimnents to travel in a lateral direction.


I f~


valpor v ..n
Extraction


Figure 1: Air sparging soil vapor extraction system.

Experimental studies of vertical gas migration through
homogenous, liquid-saturated, laboratory-scale porous
media have been conducted by previous authors. These
have often evaluated macroscopic changes in flow patterns,
such as the transition to a quasi-steady state of gaseous flow
as shown by Geistlinger et al. (2006). A review by Oostrom
et al. (2007) covers many of these unstable flow
experiments in detail. Computational studies of gaseous
flow at higher injection rates through liquid-saturated
porous media under the influence of gravitational forces
have been perfonned as well, and were usually conducted
with pore-throat models (e.g. Zhang et al. 2000; Stevenson
et al. 2004).
Experimental studies have also been performed to examine
the changes in the motion of air through liquid-saturated,
heterogeneous porous media. An investigation of the effect
of injection rates on air-sparging efficiency within a 100 cm
by 80 cm sand-box with lenses of different grade sands was


NAPL Spill






7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

labeled #1 and #2 in Figure 2. Air was injected into the
centered port of one of these manifolds and through the
initially water-saturated flow cell to perform the
experiments.
A relatively simple experimental setup was used to control
the fluid flow into the flow cell and to capture the images. A
schematic of the experimental setup is shown in Figure
3(A) and consists of the SL flow cell, a constant-rate
syringe pump (KD Scientific KDS 200), a CCD camera
(NTSC COHU 4915-400/000), lighting, a collection vessel
at atmospheric pressure, and a data acquisition computer. A
LabVIEWTM (version 7.1) module was used to control the
image-capture rate. The same experimental setup was used
by Crandall et al. (2009) to capture images of 'horizontal'
fluid motion in the flow cell (i.e. no gravitational force
effects on fluid flow). For the current study the flow cell
was changed to evaluate flow in 'vertical' positions, where
the mean fluid flow was perpendicular to the gravitational
forces and the injected air flowed along the upper region of
the flow cell.


Paper No


introduced into the initially water-saturated flow cell at
different injection rates, and the resultant distributions of air
and water were recorded with a CCD camera. The awn were
determined by matching the observed saturation
distributions with the known geometry of the flow cell. A
discussion of the experimental and processing procedures is
given in the next section, followed by the resulting
variations in the awn with both changes in flow rate and
orientation of the porous medium.

Nomenclature

A Flow cell cross-sectional area (nr)
B Bond number (-)
Interfacial area between wetting and non-wetting
awn fluids (nr)
Ca Capillary number (-)
g Gravitational force
P Pressure (Nm )
q Mean volumetric flow rate (m~s ')
Q Volumetric flow rate (m's ')


Greek letters
K Permeability (nr)
y Interfacial Tension (Nnr)
p Fluid density (kgms-1iI
CLAbsolute viscosity (Pas)

Subsripts
D Defending fluid
X, Z Directional orientations


Figure


Methods and Materials

The porous medium used for our experiments was
constructed using stereolithography (SL) rapid prototyping,
a production technique that has been used to make complex
parts from computer aided design models. SL models are
fabricated by curing successive layers of photo-sensitive
resin with a laser to form 3D objects. Our SL flow cell was
constructed using a 3D Systems Viper Si'
stereolithography apparatus out of DSM 11120 Watershed
(DSM Somos, New Castle DE, USA), a water-resistant
resin. The flow cell production procedure is reviewed in
detail by Crandall et al. (2008).
The porous matrix of the flow cell, labeled in Figure 2, was
constructed as a square-lattice of over 5000 throats within a
10.16 cm by 10.16 cm region. The individual throat widths
varied from 0.35 mm to 1.0 mm. These throat widths were
randomly distributed throughout the porous matrix. To
introduce a greater range of pore-level resistances into the
flow cell, seven different throat heights were assigned to
these throats, varying from 0.2 mm to 0.8 mm. These throat
heights were assigned in such a manner so as to reduce the
aspect ratio of the throats. That is, the narrowest throats
were assigned to be the shortest (smallest throat width =
smallest throat height), the widest throats were made the
tallest, and so forth. A detailed comparison of the throat
capillary and inertial resistances of this SL flow cell to
resistances of other flow devices in the literature is listed in
Table 1 of Crandall et al. (2008). Two manifolds were
created on opposing edges of the porous matrix, arbitrarily


(A)

Q


12-T 21-T


(B)


Figure 3: (A) Schematic of experiment. 1 Flow cell, 2 -
Syringe pump, 3 CCD Camera, 4 Lighting, 5 Exit at
atmospheric pressure, and 6 Acquisition computer.
(B) The four vertical orientations of the flow cell that were
used during the data acquisition.





7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

interfaces have been observed (M~heust et al. 2002). For
our study, where the gravitational field is perpendicular to
the mean flow direction we follow the lead of Zhang et al.
2000 and define a Bond number in the X and Z direction,


Paper No


The no-flow boundary upper boundary of the flow cell
corresponds to a low-permeability barrier, such as the lens
in Figure 1. There are four different ways of placing the
flow cell so that a no-flow upper boundary is obtained with
the manifolds on the sides. In our experiments the cell was
filled with water, and air was injected through one of the
manifolds: then the cell was refilled with water, and the
flow direction reversed by injection of air through the other
manifold. The cell then was rotated 1800, so that what had
been the bottom of the cell became the top, and the
injections were repeated. These four different ways of
aligning the flow cell provided four 'different' porous
media, with the same distribution of throat sizes and similar
macroscopic properties (e.g porosity and permeability).
These four orientations are shown schematically in Figure
3(B) and abbreviated 12-T, 12-B, 21-T, and 21-B for flow
from Manifold #1 to #2 'Top', Manifold #1 to #2 'Bottom',
Manifold #2 to #1 'Top', and Manifold #2 to #1 'Bottom',
respectively.

Experimental Conditions

Injection of air at different flow rates was conducted. The
ratio of inertial to capillary forces for the different flow rates
was quantified using the following definition of the
capillary number,


~pgxi K
7


~pgzic,
7


& B,


OUH~oo

A7


Ca D
7


where q is the mean volumetric flow across the flow cell, a ,
is the defending fluid absolute viscosity (4u = 4L,,,,,), and 7
is the interfacial tension between the injected air and the
defending water (y = 72 "/m). Here q is defined as the
injected volumetric flow rate, Q. divided by the mean
cross-sectional area of the flow cell perpendicular to the
flow direction, 4. For this study the O was varied from a
maximum of 20 m /m to a minimum of 0.2 m /m,, which
corresponds to 4.63(10-9) < Ca < 4.63(10-").
All experiments were conducted with the flow cell initially
saturated with distilled water and air injected into either
Manifold #1 or Manifold #2 at a constant rate. This fluid
pairing has a viscosity ratio (M~ = 4u,,,/4~,,,,) of 0.0178,
which indicates the drainage case studied is in the unstable
regime. When the gravitational forces and the direction of
flow are in the same direction the Bond number, B, has been
defined as (Zhang et al. 2000),

Apgic



where Ap is the difference in fluid densities, g is the
gravitational force constant, and K is the permeability of the
porous media. A similar B has been defined in the literature
using the square of the throat radius as a length scale, rather
than K (e.g. M~heust et al. 2002). When g is parallel to the
mean flow direction and B > 0, gravity stabilizes the
advancing flow front and a fairly uniform interfacial
advancement is observed. Conversely, when B < 0, gravity
destabilizes the interface and non-uniform (fractal)


where the subscripts indicate the direction. X has been
assigned the flow direction and Z the direction in which g
acts. Also, due to the random assignment of the throat sizes
throughout the flow cell, Kz = Kx. With these relationships
and the fluid properties of air and water Eq. (3) reduces to
Bx = 0 and Bz = B = 5.4 (10 )~.
Greyscale images of the air invasions were captured every
0.1s or 0.3s, depending on the flow rate. Hundreds to
thousands of images were obtained from experiments at the
three flow rates studied (Ca = 4.63(10-9), 4.63(10-'"), and
4.63(10 ")) and through the four orientations of the flow
cell (Figure 3(B)). In addition, for each of these cases three
separate experiments were performed so that the awn
calculations could be averaged. In total, 36 separate
experiments where performed.
The original greyscale images were cropped to include only
the square porous matrix, manipulated using batch
processes to isolate the pixels of invading air, and converted
to black and white images using a custom Scheme function
within the GNU Image Manipulation Program, Version 2.62.
These black and white images were then converted to
ASCII data sets using ImageJ 1.410 (National Institutes of
Health, USA). An example of this image processing
procedure is shown in Figure 4 for a single image of air
invasion from a Ca = 4.63(10-9), 12-T trial. These ASCII
files were then analyzed with an in-house to identify the
location of each interface between the fluids. These
individual interface locations were correlated to the known
throat size at each interfacial point and the individual
interfaces were estimated as the cross-sectional











(A) (B)







(C) (D)

Figure 4: Image conversion steps. (A) Original greyscale
image, (B) Air isolated image, (C) ASCII data file, and (D)
Indentified interfaces. Note that (C) and (D) are of subsets
of the entire image.









area of the throat at that location. We assume that the
interfacial areas in the corners of the rectangular throats can
be neglected (Ma et al. 1996). By summing these estimates
of the individual meniscus areas within the throats we
obtained our estimates of as,.

Results and Discussion

The calculated awraalues are reported in this section as the
plwsical area of the menisci between air and water, not the
specific interfacial area (L,), as has been reported in much
of the prior literature dealing with a,, (e.g. Hassanizadeh
and Gray, 1990: Joekar-Niasar et al. 2008: Niessner and
Hasssanizadeh, 2008). Typically the Am, is defined as the am,
per unit volume of the porous medium. For the experiments
we have performed, with air flowing adjacent to the top
no-flow boundary of the flow cell, dividing by the total
volume of the flow cell resulted in small Awnvalues. This
motion along only the top edge of the flow cell is shown in
Figure 5 for all four cell orientations. Two reasonable
procedures to estimate the Am, are 1) calculating the Aw,
within half of the flow cell volume or 2) determining m,
within the minimum rectangular-box volume that would
completely enclose the invaded air mass. By using half of
the cell volume we would be applying a consistent
volumetric quantity, 1.78 cm3, which would make
comparisons between our experiments practical, as well as
acknowledging that air flow will only occur in the upper
half of the cell. The minimum rectangular-box volume
might provide a better comparison to other literature values
which have been calculated with no g effects, where the two
fluids typically have an opportunity to flow throughout the
entire porous domain. Rather than obfuscate the recorded
values by either of these Am, definitions, we have presented
the calculated plwsical estimates of a,,, in enr. This
allows a direct comparison between observed changes in awn
due to flow rate and porous media geometry, with minimal
notational confusion.






12- 2 -T









12 B 21 B






Figure 5: Four greyscale images of the air invasion
through the flow cell for each of the different orientations.
Ca = 4.63(10 "'). The air transitions from black to light
grey with increasing time, with the lightest grey at
breakthrough.


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

Breakthrough occurred when the air reached the exit
manifold, after traversing the top of the flow cell. For the
Ca = 4.63(10-9) experiments this took approximately 20
seconds; for the Ca = 4.63(10 ") flows, the motion was
complete in several minutes.
Changes in the air saturation at breakthrough were observed
within the flow cell, as depicted in Figure 6. The five grey
hues shown in Figure 6 show the progression from the first
invaded throats (black) to the burst of air that resulted in
breakthrough (lightest grey) for one orientation of the cell.
While the overall structure of the air is quite similar
regardless of the injection rate, the fastest flow rate (Ca =
4.63(10-9)) has a noticeably lower air saturation. The
measurement of the ass,revealed that there was little change
among these flows. An average value of the ass, was
calculated from the breakthrough images of the twelve
experiments that were conducted at each Ca (three
individual experiments through each of the four cell
orientations). These are shown in Figure 7, with the vertical
error bars showing + one standard deviation of these values.
There was little change observed between different flow
rates, which can be explained by examining the air
saturations in Figure 6. While the lower Ca flows resulted in
a higher saturation, in many instances the 'fingers' of fluid
motion touched and coalesced with adjacent fingers,
reducing the overall contact of the air with the surrounding
liquid. Conversely the fingering behavior of the fastest flow
shows that numerous fingers of air pushed into the liquid
without touching adjacent air pockets, resulting in a similar
awnvalue, even with the lower air saturation. The large error
bars (i.e. the large standard deviation of measured values)
indicate that a large amount of variation between flows
through the different cell orientations occurred. The highest
Ca flows were observed to have the least variation in am,
values.

Ca=4.63(10-11)






Ca= 4.63(10 )


Figure 6: Three greyscale images of the air invasion
through the flow cell for each of the different flow rates
studied. Flow cell orientation is 12-T.


Paper No


=*-I


**" M


*BnE-O


.83E-09


Figure 7: Averaged awnfrom the twelve experiments
performed at each Ca.
















































0, ,
12*T 21*T 124B 214
Cell Orlantalkn

Figure 8: Averaged awnfrom the nine experiments
performed with each cell orientation.

Conclusions

We have performed experiments of air flowing along a
no-flow boundary within porous media initially saturated
with water, and directly measured the interfacial area
between the fluids, awn. The injection rate of the air was
varied by three orders of magnitude and the orientation of
the flow cell was changed to evaluate the effects of flow
rate and porous media geometry on the awn. Little change
was noted between the awn for flows at different injection
rates, even though the saturation of air was noticeably
smaller in the fastest trials. The largest variation in the awn
values was noted at breakthrough between different
orientations of the flow cell. This work shows the utility of
directly measuring the awn within porous media under
various flow conditions to determine what physical and
geometrical properties will aid or hinder NAPL or VOC
remediation with air sparging.

Acknowledgements

The authors extend their gratitude to Andrew Shultz for his
help with the experiments.


7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

References

Braida, W., and S.K. Ong. 2000. Influence of porous media
and airflow rate on the fate of NAPLs under air sparging.
Trans. Porous Media 38:29-42.
Brusseau, M.L., S. Peng, G Schnaar, and M.S.
Costanza-Robinson. 2006. Relationships among air-water
interfacial area, capillary pressure, and water saturation for
a sandy porous medium. Water Resour. Res. 42: WO3501.
Chen, L., and T.C.G Kibbey. 2006. Measurement of
air-water interfacial area for multiple hysteretic drainage
curves in an unsaturated fine sand. Langmuir 22(16).
Conrad, S.H., R.J. Glass, and W.J. Peplinski. 2002.
Bench-scale visualization of DNAPL remediation processes
in analog heterogeneous aquifers: surfactant floods and in
situ oxidation using permanganate. J. Contam. Hydrol.
58:13-49.
Crandall, D., G Ahmadi, M. Ferer, and D.H. Smith. 2009.
Distribution and occurrence of localized-bursts in
two-phase flow through porous media. Physica A
38:574-584.
Crandall, D., G Ahmadi, D. Leonard, M. Ferer, and D.H.
Smith. 2008. A new sterolithography experimental porous
flow device. Rev. Sci. Instrum. 79(4):044501.
Culligan, K.A., D. Wildenschild, B.S.B. Christensen, W.G
Gray, M.L. Rivers, and A.F.B. Tompson. 2004. Interfacial
area measurements for unsaturated flow through a porous
medium. Water Resour. Res. 40:W12413.
Dalla, E., M. Hilpert, and C.T. Miller. 2002. Computation of
the interfacial area for two-fluid porous medium systems.
J. Contam. Hydrol. 56:25-48.
Elder, C.R., and C.H. Benson. 1999. Air channel formation,
size, spacing, and tortuosity during air sparging. Ground
Water Monit. Rem. 19(3):171-181.
Geistlinger, H., G Krauss, D. Lazik, and L. Luckner. 2006.
Direct gas injection into saturated glass beads: transition
from incoherent to coherent gas flow pattern. Water Resour.
Res. 42:WO7403.
Hassanizadeh, S.M. and W.G Gray. 1990. Mechanics and
thermodynamics of multiphase flow in porous media
including interphase boundaries. Adv. Water Res.
13(4):169-186.
Joekar-Niasar, V, S.M. Hassanizadeh, and A. Leijnse. 2008.
Insights into the relationship among capillary pressure,
saturation, interfacial area and relative permeability using
pore-scale network modeling. Trans. Porous Media
74(2):201-219.
Kechavarzi, C., K. Soga, T. Illangasekare, andP.
Nikolopoulos. 2008. Laboratory study of immiscible
contaminant flow in unsaturated layered sands. Vadose
Zone J. 7(1):1-9.
King, R.B., GM. Long, and J.K. Sheldon. 1992. Practical
Environmental Bioremediation. pp. 103-113. Lewis
Publishers, Boca Raton.
Ma, S., G Mason, and N.R. Morrow. 1996. Effect of contact
angle on drainage and imbibition in regular polygonal tubes.
Colloids and Surfaces A 117:273-291.
M~heust, Y., G Lovoll, K.J. 11 iloy and J. Schmittbuhl.
2002. Interface scaling in a two-dimensional porous
medium under combined viscous, gravity, and capillary
effects. Phys. Rev. E 66:051603.
Niessner, J., and S.M. Hassanizadeh. 2008. A model for
two-phase flow in porous media including fluid-fluid


Paper No


Prior to performing the experiments, we had assumed that
differences in the air flow through the porous media would
vary negligibly with changes in the cell orientation. We
performed these additional experiments to have a larger
number of experiments at each Ca to average, reducing the
statistical variability of the measurements. After analyzing
the data we found distinct changes in the observed awn with
changes in cell orientation. These are plotted in Figure 8 as
the average of the calculated awn obtained from the nine
experiments conducted for each of the four cell orientations.
Again, the vertical error bars show + one standard deviation
of the recorded values. The largest difference was observed
between 'Top' and 'Bottom' flows, with the 'Top'
orientation resulting in a consistently higher awnvalue. The
variability observed was less than the variability observed at
each Ca, as shown by the smaller standard deviation of
averaged results in Figure 8 compared to Figure 7. These
results largely confirm the results of Waduge et al. (2007),
where little change in air-NAPL remediation was observed
over the investigated range of air flow rates but different
permeabilities (i.e. geometries) did effect the NAPL removal
rates.


1750


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Paper No 7th International Conference on Multiphase Flow
ICMF 2010, Tampa, FL USA, May 30-June 4, 2010

interfacial area. Water Resour. Res. 44, WO8439.
Oostrom, M., J.H. Dane, and T.W. Wiestsma. 2007. A
review of multidimensional, multifluid, intermediate-scale
experiments: flow behavior, saturation imaging, and tracer
detection and quantification. Vadose Zone J. 6(3):610-637.
Powers, S. E., L.M. Abriola, and W.J. Weber, Jr. 1992. An
experimental investigation of nonaqueous phase liquid
dissolution in saturated subsurface systems: steady state
mass transfer rates. Water Resour. Res. 28(10)2691-2705.
Reddy, K.R., R. Semer, and J.A. Adams. 1999. Air flow
optimization and surfactant enhancement to remediate
toule-contaminated saturated soils using air sparging.
Enviro. Manage. Health 10/1, 52-63.
Rogers, S.W. and S.K. Ong. 2000. Influence of porous
media, airflow rate, and air channel spacing on benzene
NAPL removal during air sparging. Environ. Sci. Technol.
34(5):764-770.
Stevenson, K., G.S. Bromhal, M. Ferer, J. Wilder, and D.H.
Smith. 2004. Miscible, vertical network model 2-D
simulations of two-phase flow displacements in porous
media. Physica A 343:.317-3 34.
Waduge, W.A.P, K. Soga, and J. Kawabata. 2007. Physical
modeling of LNAPL source zone remediation by air
sparging. Vadose Zone J. 6:413-422.
Zhang, Y., M. Shariati, and Y C. Yortsos. 2000. The
spreading of immiscible fluids in porous media under the
influence of gravity. Trans. Porous Media 38:117-140.




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