Making a Simple A+B→C Reaction Oscillate by Coupling to Hydrodynamic Effect

Abstract

We present a new mechanism through which chemical oscillations and waves can be induced in batch conditions with a simple A þ B → C reaction in the absence of any nonlinear chemical feedback or external trigger. Two reactants A and B, initially separated in space, react upon diffusive contact and the product actively fuels in situ convective Marangoni flows by locally increasing the surface tension at the mixing interface. These flows combine in turn with the reaction-diffusion dynamics, inducing damped spatiotemporal oscillations of the chemical concentrations and the velocity field. By means of numerical simulations, we single out the detailed mechanism and minimal conditions for the onset of this periodic behavior. We show how the antagonistic coupling with buoyancy convection, due to concurrent chemically induced density changes, can control the oscillation properties, sustaining or suppressing this phenomenon depending on the relative strength of buoyancy-and surface-tension-driven forces. The oscillatory instability is characterized in the relevant parametric space spanned by the reactor height, the Marangoni (Ma i ) and the Rayleigh (Ra i ) numbers of the ith chemical species, the latter ruling the surface tension and buoyancy contributions to convection, respectively.

Propagating fronts in fluids with solutal feedback

“…Reacting fronts that propagate through a moving fluid are important parts of many systems in science and engineering that are of intense current interest [1][2][3]. This includes geophysical problems such as the lock-exchange instability [4,5] of oceanic and atmospheric flows, the buoyancy and surface tension driven flows of chemical fronts [3,[6][7][8][9], the propagation of polymerization fronts [10], the rich spatiotemporal dynamics of forest fires [11,12], and the improved properties of combustion of pre-mixed gases in a turbulent fluid flow [13][14][15].…”

Persistence of quantum violation of macrorealism for large spins even under coarsening of measurement times

“…On the other hand, the treatment presented in this paper consists of three stages: (a) For a N (= 2 j + 1) level system, we consider the measurements that project the state of the system onto one of the N subspaces. In other words, we consider the case of a complete degeneracy-breaking measurement [67], as initially proposed by von-Neumann [74,75]. (b) Subsequently, for our analysis, in order to take into account the coarsening of individual measurement outcomes, we club the different outcomes into two groups.…”

“…This observable quantity Q is measured at instances t 1 , t 2 and t 3 (t 1 < t 2 < t 3 ). Note that this type of grouping scheme has been used earlier in the treatments of the quantum violation of macrorealism [41,67,70]. Note that the above measurement scheme has been critically reexamined in the context of Leggett-Garg inequality by Kumari et al [72].…”

“…For instance, in the case of spatial quantum correlations pertaining to spatially separated particles, it has been demonstrated that quantum features in the form of quantum violations of local realist inequalities persist in the 'macroscopic' limit, such as for the large number of constituents of the entangled system or for the large dimensions of the constituents of the entangled system [58][59][60][61][62][63][64][65]. On the other hand, in the case of temporal correlations, it has been shown that the quantum violation of Leggett-Garg inequality persists for arbitrary large value of spin of the system under consideration [66][67][68].…”

Leggett-Garg inequality in the context of three flavor neutrino oscillation

“…It was shown in [27] that this bound holds for systems with arbitrary (but finite) number of levels, as long as the measurements are given by just two projectors [28][29][30][31]. In the limit N → ∞, LGI can be violated up to its maximum algebraic sum [32].…”