Convection in chemical waves

Vasquez, Desiderio A.; Littley, J. M.; Wilder, Joseph W.; Edwards, Boyd F.

doi:10.1103/physreve.50.280

Cited by 67 publications

(56 citation statements)

References 10 publications

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“…The problem in the cylinder is much more complicated because of its three-dimensional nature and the singularity at the origin in cylindrical coordinates. Our previous calculations for the iodate-arsenous acid reaction in a twodimensional slab [9] predicted a critical width for the onset of convection that agrees with experiments in a cylinder. The experimental measurements in petri dishes using two-dimensional spectrophotometery [6] [10].…”

Section: Introductionsupporting

confidence: 50%

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Convective chemical-wave propagation in the Belousov-Zhabotinsky reaction

et al. 1995

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Section: Introductionsupporting

confidence: 50%

“…The chemical-wave speed increases monotonically with the slab width as shown in Fig. 8 [5] for fronts in the chlorite-thiosulfate reaction and has also been reported in the numerical simulations in the iodate-arsenous acid reaction [9]. A qualitative explanation has been proposed [5].…”

Section: Horizontal and Tilted Slabsmentioning

confidence: 74%

Convective chemical-wave propagation in the Belousov-Zhabotinsky reaction

et al. 1995

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“…Although the effects of convection on the propagation of autocatalytic fronts have been widely studied theoretically and numerically (see Vasquez et al, 1994;Vladimirova and Rosner, 2003;Rongy et al, 2007 and references therein), the influence of convection on the dynamics of simpler A þ B-C reaction fronts has not been addressed in detail yet. In this framework, Rongy et al (2008) recently studied the influence of convection in the case where the reactants A and B have equal diffusion coefficients and equal initial concentrations for which the RD analysis predicts a non-moving front.…”

Section: Introductionmentioning

confidence: 99%

Influence of buoyancy-driven convection on the dynamics of A+B→C reaction fronts in horizontal solution layers

Rongy

Trevelyan

Wit

2010

Chemical Engineering Science

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a b s t r a c tThe dynamics of initially vertical A þ B-C reaction fronts propagating in covered horizontal solution layers can be influenced by buoyancy-driven convection. Experiments have provided evidence that a much faster propagation of the front occurs in solutions than that predicted by reaction-diffusion (RD) theories, thereby suggesting the influence of convective effects arising if A, B, and C have different densities. Here we analyze numerically and theoretically the dynamics resulting from the coupling of a simple A þ B-C chemical reaction with diffusion and convection induced by density differences across the reaction front. The important parameters of the related reaction-diffusion-convection (RDC) model are the three dimensionless Rayleigh numbers, quantifying the contribution of each species concentration to the density of the solution, the layer thickness, and the initial reactant concentration ratio. The presence of buoyancy-driven convection at the front induces a propagation of this front even in the case of equal diffusion coefficients and equal initial reactant concentrations for which RD theories predict a non-moving front. In the case of equal initial concentrations, even in the presence of convection, the classification of the various possible dynamics and the prediction of the direction of front propagation can be obtained from simple criteria on the Rayleigh numbers. In the case of different initial reactant concentrations for which, in the absence of convection, the RD front propagates towards the side of the less concentrated reactant, the introduction of buoyancy convection not only invalidates the long time RD scalings but can lead to a double reversal in the direction of propagation of the reaction front for intermediate times. The influence of the different parameters on the RDC dynamics is presented.

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“…In closed horizontal solution layers (no surface open to air), convection triggered by the density jump across a propagating front has been shown both experimentally [30][31][32][33][34] and numerically [35][36][37][38][39][40][41] to deform and to speed up this front in isothermal conditions. When the reaction is exothermic, the combination of solutal and thermal density changes comes into play and has been noted to affect for instance the propagation of polymerization fronts in horizontal layers 42,43 and to result in new dynamical behaviors for the case of chemical fronts of the chlorite-tetrathionate (CT) reaction [44][45][46] and of the IAA reaction.…”

Section: Introductionmentioning

confidence: 99%

Marangoni-driven convection around exothermic autocatalytic chemical fronts in free-surface solution layers

Rongy

Assemat

Wit

2012

Chaos: An Interdisciplinary Journal of Nonlinear Science

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Segmented waves in a reaction-diffusion-convection system Chaos 22, 037109 (2012) Instability in evaporative binary mixtures. I. The effect of solutal Marangoni convection Phys. Fluids 24, 094101 (2012) Coalescence of surfactant covered drops in extensional flows: Effects of the interfacial diffusivity Phys. Fluids 24, 082101 (2012) Transient Rayleigh-Bénard-Marangoni solutal convection Phys. Fluids 24, 074108 (2012) Additional information on Chaos Gradients of concentration and temperature across exothermic chemical fronts propagating in free-surface solution layers can initiate Marangoni-driven convection. We investigate here the dynamics arising from such a coupling between exothermic autocatalytic reactions, diffusion, and Marangoni-driven flows. To this end, we numerically integrate the incompressible Navier-Stokes equations coupled through the tangential stress balance to evolution equations for the concentration of the autocatalytic product and for the temperature. A solutal and a thermal Marangoni numbers measure the coupling between reaction-diffusion processes and surface-driven convection. In the case of an isothermal system, the asymptotic dynamics is characterized by a steady fluid vortex traveling at a constant speed with the front, deforming and accelerating it [L. Rongy and A. De Wit, J. Chem. Phys. 124, 164705 (2006)]. We analyze here the influence of the reaction exothermicity on the dynamics of the system in both cases of cooperative and competitive solutal and thermal effects. We show that exothermic fronts can exhibit new unsteady spatio-temporal dynamics when the solutal and thermal effects are antagonistic. The influence of the solutal and thermal Marangoni numbers, of the Lewis number (ratio of thermal diffusivity over molecular diffusivity), and of the height of the liquid layer on the spatio-temporal front evolution are investigated. As a chemical reaction induces changes in the temperature and in the composition of the reactive medium, it can modify the properties of the solution (density, viscosity, surface tension) and thereby trigger convective motions, which in turn affect the reaction. Such a coupling can typically be observed around reactive interfaces in liquid solutions. Two classes of convective flows are then commonly developing in solutions open to air, namely Marangoni flows arising from surface tension gradients and buoyancy flows driven by density gradients. As both flows can be induced by compositional changes as well as thermal changes and in turn modify them, the resulting experimental dynamics are often complex. The purpose of our study is to gain insight into these intricate dynamics thanks to the theoretical analysis of model systems where only one type of convective flow is present. We address here the dynamics of an exothermic autocatalytic front propagating in the presence of Marangoni flows, when the density remains uniform. The surface tension gradient across the front has both a thermal component linked to the exothermicity of the reaction and a s...

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Convection in chemical waves

Cited by 67 publications

References 10 publications

Convective chemical-wave propagation in the Belousov-Zhabotinsky reaction

Convective chemical-wave propagation in the Belousov-Zhabotinsky reaction

Influence of buoyancy-driven convection on the dynamics of A+B→C reaction fronts in horizontal solution layers

Marangoni-driven convection around exothermic autocatalytic chemical fronts in free-surface solution layers

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