Propagation of chemical wave

Figure Bl.14.5. J2-weighted images of the propagation of chemical waves in an Mn catalysed Belousov-Zhabotinsky reaction. The images were acquired in 40 s intervals (a) to (1) using a standard spin echo pulse sequence. The slice thickness is 2 nun. The diameter of the imaged pill box is 39 nun. The bright bands...

Figure 4. Propagation of chemical wave in the rectangular poly(NIPAAm-co-...

In general, the skeletal Oregonator model or the Oregonator -like models describe the experimental data. Nevertheless the precise description of the experimental results is achieved when more extended kinetic models for the B-Zh reaction are used (see, for example [27-32]). At that the propagation of chemical waves in the reactor space (spatial periodicity) is described by the diffusion equations [48-50]. 

Peristaltic Motion of Cels with Propagation of Chemical Wave... 

Microfabrication of self-oscillating gel has also been attempted by lithography for application to a ciliary motion actuator (artificial cilia) [30]. The gel membrane with microprojection array on the surface was fabricated by utilizing X-lay lithography (LIGA). With the propagation of chemical wave, the microprojection array exhibits dynamic rhythmic motion hke ciha. The actuator may also serve as a microconveyor. 

This reaction can oscillate in a well-mixed system. In a quiescent system, diffusion-limited spatial patterns can develop, but these violate the assumption of perfect mixing that is made in this chapter. A well-known chemical oscillator that also develops complex spatial patterns is the Belousov-Zhabotinsky or BZ reaction. Flame fronts and detonations are other batch reactions that violate the assumption of perfect mixing. Their analysis requires treatment of mass or thermal diffusion or the propagation of shock waves. Such reactions are briefly touched upon in Chapter 11 but, by and large, are beyond the scope of this book. 

Propagation problems. These problems are concerned with predicting the subsequent behavior of a system from a knowledge of the initial state. For this reason they are often called the transient (time-varying) or unsteady-state phenomena. Chemical engineering examples include the transient state of chemical reactions (kinetics), the propagation of pressure waves in a fluid, transient behavior of an adsorption column, and the rate of approach to equilibrium of a packed distillation column. 

In other words, investigation of explosives involves a study of these aspects. For example, an investigation of the potential energy involves study of thermochemistry of the chemical compound in question. Further, the power and sensitiveness of an explosive depend on properties such as heat of formation and heat of explosion . An investigation of the feature (2) involves measurement of the rate of propagation of explosion waves and all phenomena in the proximity of detonating mass of the explosive. This rate of decomposition largely determines the pressure... 

The previous chapters have discussed the behaviour of non-linear chemical systems in the two most familiar experimental contexts the well-stirred closed vessel and the well-stirred continuous-flow reactor. Now we turn to a number of other situations. First we introduce the plug-flow reactor, which has strong analogies with the classic closed vessel and which will also lead on to our investigation of chemical wave propagation in chapter 11. Then we relax the stirring condition. This allows diffusive processes to become important and to interact with the chemistry. In this chapter, we examine one form of the reaction-diffusion cell, whose behaviour can be readily understood by comparison with the responses observed in the CSTR. 

Velocity of detonation dependent on diameter of explosive charge, i.e. critical diameter Does not usually revert to deflagration, if propagation of detonation wave fails explosive composition remains chemically unchanged... 

On the Propagation of Shock Waves in a Gas with Reversible Chemical Reactions ... 

The propagation of shock waves accompanied by an irreversible chemical reaction with substantial release of heat is the subject of the theory of detonation [3-6]. 

A quantitative measure of the interaction of chemical waves and steady electric fields is the velocity response curve, i.e. a plot of the dependence of a plane wave velocity on the electric field applied along the direction of propagation. Note that in Figure 8 the curve measured for a modification of the BZ medium terminates at around 10 volts/cm (for waves propagating toward the negative electrode) since for larger fields the waves are annihilated. Further details on these measurements are found in Ref. 1 where the special chemical wave medium recipes developed to make the measurements are given. 

Fin. 10.1.2 Displace mem-irr.vH.v-ti me plots of chemical waves. l,efl schematic illustration of the coiistructioii by slacking ID projcction.s. Right chemical waves propagating down wards in the sample tube. The vertical coordinate is the lield of view with a range of 70 mm, the horizontal coordinate is time (2S6 s). The velocity i of the waves is about 2.7 0.2 mm/inin. Adapted from [T7.a2 with permission from Flsevier Science. 

A common example is the Belousov - Zhabotinsky reaction [24], Beautiful patterns of chemical wave propagation can be created in a chemical reaction - diffusion system with a spatiotemporal feedback. The wave behavior can be controlled by feedback-regulated excitability gradients that guide propagation in the specified directions [25, 26]. 

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