Transcript Diapositiva 1 - New Jersey Institute of Technology

Density fingering of reaction-diffusion fronts
in porous media
L. Macias; D. Müller; N. Berrueta; L. Riolfo and A. D'Onofrio
Grupo de Medios Porosos,Facultad de Ingeniería, Universidad de Buenos Aires,
Argentina
In collaboration with:
A. De Wit
P. Trevelyan
Université Libre de Bruxelles
A. Zalts
C. El Hasi
D. Rubio
Universidad Nacional General Sarmiento
Objectives
Experimental study of
two kinds
Rayleigh-Taylor instability
on of reactions
reaction-diffusion fronts
a simple exothermic neutralization reaction,
NaOH solution and HCl solution (Acid-Base)
the acid autocatalysis of Chlorite-Tetrathionate (CT).
• Hele-Shaw cells and Porous Media
What is the difference between the two kinds of reaction?
• Chemical kinetic constant q
• The main difference is the stationary travelling wavefront
Acid - Base
CT
qAB = 1.4×1011 M-1s-1
qCT = 2.4×104 M-3s-1
reactants
product
position
P. Trevelyan, A. De Wit.
concentration
concentration
product
V
reactants
position
J. Yang, A. D´Onofrio, S. Kalliadasis, A. de Wit. J.
Chem. Phys. 117, 9395 (2002)
Rayleigh – Taylor instability modified by chemical reaction
in the interface
without
with chemical reaction
chemical reaction
g
Grupo de Medios Porosos, FIUBA (2002)
Grupo de Medios Porosos, FIUBA (2004)
Rayleigh – Taylor instability modified by chemical reaction
in the interface
Rayleigh – Taylor instability
modified by chemical reaction
in the interface
without
with chemical reaction
chemical reaction
r
product
g
reactants
x
Density profile
Mixing zone is smaller
D. Lima, A. D´Onofrio, A. De Wit, J. Chem. Phys. 124, 014509 (2006)
Effect of temperature (CT reaction)
Chlorite-Tetrathionate (CT)
Is an exothermic reaction
thermals effects are very
important
Effect of temperature (CT reaction)
Temperature
1 cm
1c
m
t = 80s
t = 140s
t=
140s
t = 210s
t=
140s
t=
210s
T = 12.4ºC
T = 20.5ºC
T = 39.4ºC
G. Garcia Casado, L. Tofaletti, D. Müller, A. D´Onofrio,. J. Chem. Phys. 126, 114502 (2007)
Effect of temperature (CT reaction)
G. Garcia Casado, L. Tofaletti, D. Müller, A. D´Onofrio,. J. Chem. Phys. 126, 114502 (2007)
Effect of temperature (CT reaction)
G. Garcia Casado, L. Tofaletti, D. Müller, A. D´Onofrio,. J. Chem. Phys. 126, 114502 (2007)
Front evolution at the inlet of the porous medium
(CT reaction)
Mixing zone
Helle shaw cell
t (s)
Porous medium
3.5 cm
Grupo de Medios Porosos, FIUBA (2006)
Acid - Base reaction
r
r
product
Acid
g
reactants
x
Density profile CT reaction
Base
x
Density profile Acid
- Base reaction
Acid - Base reaction
Acid
Base
rA < rB
4.5 cm
A. Zalts, A Ureña, D. Rubio, C. El Hasi, A. D´Onofrio. PRL (sent to publish)
Acid - Base reaction
Acid - Base reaction
Equation of system
Numerical results
Base
Acid
g
P. Trevelyan, A. De Wit.
1 cm
Acid - Base reaction
t=490min
t=2520min t=6650min
0.1M
t=490min
t=2518min
0.03M
t=6648 min
t=260 min
t=2518min
0.01M
t=6648min
Acid - Base reaction
Acid - Base reaction
Variations of the mixing zone as a function of
time for different concentrations.
Power spectra of the fingers for different
concentrations. Note that the basic modes increases
when the solution concentration increases.
Conclusion
Acid - Base reaction
• The Rayleigh – Taylor instability is modified by chemical reactions in
the interface producing a decrease of the mixing zone (CT reaction).
• Temperature is a very important factor in this kind of systems as it
could produce the disappearance of the instability (CT reaction).
• Even with an initial stable density profile, this chemical reaction (Acid
– Base reaction) develops instabilities.
• In the Acid – Base case the mixing zone increases when the concentration
decreases.