Stability of exothermic autocatalytic fronts with regard to buoyancy-driven instabilities in presence of heat losses

Gérard, T.; Wit, A. De

doi:10.1016/j.wavemoti.2011.04.018

Cited by 4 publications

(3 citation statements)

References 42 publications

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“…Therefore, the Schmidt number can vary from 1246 at T = 4 • C to 138 at T = 50 • C. We set the Schmidt number to S c = 400, which is close to experimental values for the iodate-arsenous acid systems [9]. This value can be considered constant since the change in temperature across the front is of the order of 0.1 • C. We use a Lewis number L e = 20 which is somewhat larger than typical values for the CT reaction (L e = 10) [14,15,31], but smaller than values for the IAA reaction (50 ≤ L e ≤ 70) [9,32]. In the case of an exothermic reaction with a reaction front moving upwards, the warmer fluid is underneath the front.…”

Section: Linear Stability Analysismentioning

confidence: 53%

Thermally Driven Convection Generated by Reaction Fronts in Viscous Fluids

Vilela,

Guzman,

Vasquez

2024

Symmetry

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Reaction fronts propagating in liquids separate reacted from unreacted fluid. These reactions may release heat, increasing the temperature of the propagating medium. As fronts propagate, they will induce density changes leading to convection. Exothermic fronts that propagate upward increase the temperature of the reacted fluid located underneath the front. For positive expansion coefficients, the warmer fluid will tend to rise due to buoyancy. In the opposite case, for fronts propagating downward with the warmer fluid on top, an unexpected thermally driven instability can also take place. In this work, we carry out a linear stability analysis introducing perturbations of fixed wavelength. We obtain a dispersion relation between the perturbation wave number and its growth rate. For either direction of propagation, we find that the front is stable for very short wavelengths, but is unstable for large enough wavelengths. We carry out a numerical solution of a cubic reaction–diffusion–advection equation coupled to Navier–Stokes hydrodynamics in a two-dimensional rectangular domain. We find transitions between the non-axisymmetric and axisymmetric fronts increasing with the width of the domain.

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Section: Linear Stability Analysismentioning

confidence: 53%

Thermally Driven Convection Generated by Reaction Fronts in Viscous Fluids

Vilela,

Guzman,

Vasquez

2024

Symmetry

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“…In the opposite scenario, when chemical fronts propagate downward, different pattern formation is observed: since the product solution has greater density, the propagating planar fronts are hydrodynamically unstable, resulting in a cellular structure. Figure a shows the spatiotemporal pattern formation that has been studied and understood in the past years both experimentally − and theoretically. − These structures can be characterized by their wavelength (λ) and their amplitude or mixing length ( L m ) defined as the standard deviation of the front position in the direction of front propagation. At a glance, we can find that the wavelength increases in time, while the change in the mixing length is not that obvious.…”

Section: Resultsmentioning

confidence: 99%

Self-Assembly of Charged Nanoparticles by an Autocatalytic Reaction Front

et al. 2015

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In this work we present that aggregation of charged and pH sensitive nanoparticles can be spatiotemporally controlled by an autonomous way using the chlorite-tetrathionate autocatalytic front, where the front regulates the electrostatic interaction between nanoparticles due to protonation of the capping (carboxylate-terminated) ligand. We found that the aggregation and sedimentation of nanoparticles in liquid phase with the effect of reversible binding of the autocatalyst (H(+)) play important roles in changing the front stability (mixing length) and the velocity of the front in both cases when the fronts propagate upward and downward. Calculation of interparticle interactions (electrostatic and van der Waals) with the measurement of front velocity revealed that the aggregation process occurs fast (within a few seconds) at the front position.

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“…Because of these heat losses, the temperature profile during the propagation of the front is not a front anymore but a pulse. This modification of the temperature profile can lead to a change in the stability of fronts 6,12,[19][20][21] and in their nonlinear dynamics 19,20,22 . In addition, this interferometric method has also revealed that the maximum of temperature reached in the fingered front is larger than that observed in stable planar fronts.…”

Section: Introductionmentioning

confidence: 99%

Hot spots in density fingering of exothermic autocatalytic chemical fronts

et al. 2012

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Measurements of two-dimensional (2D) temperature fields are performed by an interferometric method during density fingering of the autocatalytic chlorite-tetrathionate reaction in a Hele-Shaw cell. These measures confirm that, because of heat losses through the glass walls of the reactor, the temperature profile across the front is a pulse rather than a front. Moreover, the full 2D temperature field shows the presence in the reactive zone of hot spots where the temperature exceeds the maximum temperature measured in a stable planar front. We investigate here experimentally the increase of temperature in the hot spots when the composition of the reactants is varied to increase the exothermicity of the reaction. We back up these experimental observations by nonlinear simulations of a reaction-diffusion-convection model which show that the maximum temperature reached in the system depends on the intensity of convection.

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Stability of exothermic autocatalytic fronts with regard to buoyancy-driven instabilities in presence of heat losses

Cited by 4 publications

References 42 publications

Thermally Driven Convection Generated by Reaction Fronts in Viscous Fluids

Thermally Driven Convection Generated by Reaction Fronts in Viscous Fluids

Self-Assembly of Charged Nanoparticles by an Autocatalytic Reaction Front

Hot spots in density fingering of exothermic autocatalytic chemical fronts

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