Download Thesis - Université Paris-Sud

Discipline Physics/Geophysics/Biology
(eg: Mathematics, Physics, Biology….)
Doctoral School
MIPEGE
Thesis subject title:
Hydrodynamic Dispersion of bacteria in Porous Media
Laboratory name and web site: Fluides, Automatique et Systèmes Thermiques
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http://www.fast.u-psud.fr
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PhD supervisor (contact person):
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Name: AURADOU
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Position: CNRS Researcher
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email: [email protected]
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Phone number: 00 33 1 69 15 80 84
Thesis proposal (max 1500 words):
The project is motivated by the growing activity around biological fluids or fluids containing microorganisms and their implications for environmental issues such as bio remediation, bio technology
and the spreading of diseases caused by pathogenic microorganisms. To date only few experiments
have been devoted to the study of bacterial transport in porous media or in fractures and none takes
into account non-Newtonian rheological properties associated to collective motions of bacteria in
such fluids.
The objective of this thesis is to understand better the displacement of bacteria through porous
media in order to improve the predictions of their transport within the subsurface. For this purpose,
different flow geometries of increasing complexity will be considered in order to determine the
physical parameters characterizing the dispersion of bacteria suspensions.
The flow cells used in the present study are capillary tubes, sintered porous materials and
transparent micromodels. Using transparent models will allow for observations at the pore level and
for measurements of the bacterial concentration. Initially, models will be filled by a pure fluid (ie. in
which no micro organisms are present). The same fluid containing a chosen concentration of
bacteria will then be injected at a fixed flow rate. The sharp front separating the two fluids spreads
out with time and the dynamics of the spreading will be studied as a function of the flow rate and for
different bacteria concentration. These experimental observations will then be compared to those
made using a passive tracer (in these cases the bacteria are simply “killed” or replaced by a dye)
and with the solutions of the classical advection/dispersion model. Due to the Non Newtonian
rheology of the biological fluids and the fact that, for bacteria, the Brownian motion is sub-dominant
with respect to that induced by the agitation of flagella, a non trivial variation of the dispersion
coefficient with the Péclet number (ratio of the advective and diffusive flux) is expected.
At first, experiments will be performed in a capillary tube; for this geometry, the flow structure is
known and analytical models can be developed, allowing for quantitative comparisons with the
experimental observations. In a second phase, a porous medium made of glass beads will be
considered. In this case, mixing at the pore junction and the variation of the velocity along
streamlines become important factors influencing the dispersion. Finally, dispersion will be studied in
a single fracture. In this geometry the channelization of the flow is important leading to early first
arrival times at the fracture outlet.
Together with video measurements, the electrical response of the suspension will be studied by
performing spectral induced polarization (SIP) in a range of frequency going fom 0.1 Hz up to a kHz.
This measurement will provide information on the concentration of living bacteria and their
distribution in the pore space. Moreover, these results will be key to understand the electrical
signature of these biological components and may help to improve the measurement techniques
used in the the field.
In the present study Escherichia coli strains will be used. These bacteria are motile (they swim using
a flagella), rod-shaped, and have approximate dimensions of 1 microns in diameter by 2 microns in
length. The students will first learn to master the preparation of these fluids under the supervision of
Pr. Eric Clément. Complementary experiments using microfluidic cells available in Pr. Clément lab
may also be performed. The micromodels, used in this study will be made using the technique
(micro milling, 3D printing...) available at the FAST. 16Bits Video cameras and microscope are also
available as well as equipments such as rheometer, densimeter, PIV (Particle Image Velocimetry) or
LIF (Laser Induced Fluorescence)... Electrical measurements will be performed using the
equipments of platform PEPS maintained by FAST and IDES.
Presentation of the FAST:
The FAST (Fluides, Automatique et Systèmes Thermiques) is a CNRS research laboratory (UMR
7608), associated to the Pierre and Marie Curie - Paris 6 and the Paris-Sud 11 Universities. The
research domains of the lab are hydrodynamics, transfer, and mechanics and hydrodynamics of
dispersed media. The systems studied are simple or multicomponent fluids, macroscopic dispersed
media (suspensions, granular materials, porous media, fractures...) and soft condensed matter
(polymers, colloids, gels...). Experiments (flow visualisation, quantitative image analysing, acoustic
investigations, high resolution gravimetry, rheology...) as well as analytical models and numerical
simulations are developed.
The research areas are
- Porous and Fractured Media
- Granular Materials and Suspensions
- Heat and Fluid Flow
- Instabilities and Turbulence
Presentation of the Porous and Fractured Media team:
The team studies flow and transport in porous media and fractures. Experiments are coupled to
numerical modeling using Lattice Boltzman or Finite Element Methods codes. Our work has
applications to Earth sciences, especially in hydrology (dispersion of pollutant), geothermy (Soultzsous-Forêts), oil recovery (with the IFP and Schlumberger), sequestration of CO2 (ANR COLINER).
The processes studied are hydrodynamic dispersion, chemical reactions, particle transport, flow of
complex fluids, drying and failure. At these scales, the influence of velocity fluctuations is important
and descriptions using statistical physics tools (percolation, critical paths ...) are often needed. The
team has organized national and international scientific meetings and summer schools.
Co-supervisors:
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Fluid preparation and rheological characterization: Pr. Eric Clément, Lab. Physique et
Mécanique des Milieux Hétérogènes (PMMH), Ecole Supérieure de Physique et Chimie,
eric.clement[@]upmc.fr
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Electrical measurements: Marc Pessel, Lab. Interactions et Dynamique des Environnements
de Surface (IDES), Université Paris Sud, marc.pessel[@]u-psud.fr
Collaboration:
- Grupo de Medio Porosos, University of Buenos Aires (Argentine), through the International Lab.
“Physique et Mécanique des Fluides”.
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Publications of the laboratory in the field (max 5):
[1] Talon L., Auradou H et Hansen A. “Relation Between First Arrival Time and Permeability in SelfAffine Fractures” accepted to EuroPhysics Letters (2012)
[2] G. Lekmine, M. Pessel and H. Auradou, “Experimental study of ERT monitoring to measure
solute dispersion”, Ground Water (2011) doi: 10.1111/j.1745-6584.2011.00837.x
[3] Boschan A., Ippolito I., Chertcoff R., Hulin J-P., Auradou H. “Characterization of fracture void
space heterogeneity by electrical impedance measurements”, Journal for Contaminant Hydrology
123 (2011) 65--75.
[4] Auradou H. “Influence of wall roughness on the geometrical, mechanical and transport properties
of a single fractures”, J. Phys. D: Appl. Phys. 42 (2009) 214015.
[5] Boschan A., Auradou H., Ippolito I., Chertcoff R. and Hulin J.P. “Experimental evidence of the
anisotropy of tracer dispersion in rough fractures with sheared walls”, Water Resour. Res. 45 (2009)
W03201
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Specific requirements to apply, if any:
The position will suit candidates with a background in fluid mechanics or in microbiology. Good
written and oral communication skills in English are a plus.
A strong taste for laboratory experiments is needed.