Relation between shape of liquid-gas interface and evolution of buoyantly unstable three-dimensional chemical fronts

Abstract

Buoyantly unstable 3D chemical fronts were seen traveling through an iodate-arsenous acid reaction solution. The experiments were performed in channel reactors with rectangular cross sections, where the top of the reaction solution was in contact with air. A concave or convex meniscus was pinned to reactor lateral walls. Influence of the meniscus shape on front development was investigated. For the concave meniscus, an asymptotic shape of fronts holding negative curvature was observed. On the other hand, fronts propagating in the solution with the convex meniscus kept only positive curvature. Those fronts were also a bit faster than fronts propagating in the solution with the concave meniscus. A relation between the meniscus shape, flow distribution, velocity, and shape is discussed.

Effects of the Starch Indicator on the Buoyantly Unstable Iodate‐Arsenous Acid Reaction Front

“…The reaction solution depth varied from 1.5 mm to 31 mm. Like in previous experiments,, the autocatalytic reaction was initiated immediately after filling of the reactor. The pipet tip, which contained 20 ml of the reaction products, was carefully and slowly moved towards the reaction solution until it got in contact with the liquid surface (inoculation).…”

“…Stock solutions were kept at constant temperature 21° ± 1° C. For experiments performed in channel reactors, the freshly prepared reaction mixtures consisted of 0.016 M Na 3 AsO 3 , 0.016 M H 2 SO 4 , and 0.005 M NaIO 3 , which gives the stoichiometric ratio =3.2. The concentrations are chosen the same as those used in our previous experiments . They also correspond to experiments performed in testing tubes ,.…”

“…The flow pushes the ascending fronts up, which speeds up movement of the front and leads to formation of many fingers ,,. The originally vertical fronts are due to the convection tilted and their movement is faster than the descending ones ,,,. The tilted fronts are accompanied with convection rolls which travels together with the fronts ,.…”

“…The numerical studies described the front behavior for thin solution layers, where was up to 3 mm, while the experiments were performed for up to=2 cm . Effect of the free surface deformation on the buoyantly unstable IAA reaction front propagation was also studied . For chosen solution depth the surface deformation influenced only the shape of the reaction front.…”

“…Under such condition, 3D experiments could be compared to 2D simulation. To profit from our previous study, we used the same composition of the reaction mixture and reactor cells at which the upper surface of the reaction solution is open to air . Moreover, the used ratio =3.2 should guarantee that the Marangoni effect will be suppressed, because the surface active iodine is only intermediate and should not accumulate in the solution.…”