Instability diffusion

Real-life premixed flame fronts are rarely planar. Of course, if the flow is turbulent, gas motion will continuously deform and modify the geometry of the flame front, see Chapter 7. However, even when a flame propagates in a quiescent mixture, the front rapidly becomes structured. In this chapter, we will discuss hydrodynamic flame instability, thermo-diffusive instability, and thermo-acoushc instability. 

A correlation between the spacing of striae and convection downstream of protrusions does not fully describe the process. The initial protrusions arise far from transport control and cannot be attributed to a diffusive instability of the type described in the previous section. Jorne and Lee proposed that striations formed on rotating electrodes by deposition of zinc, copper and silver are generated by an instability that arises only in systems in which the current density at constant overpotential decreases with increasing concentration of metal ion at the interface [59]. 

Diffusive instability can appear in simple predator-prey models. Bartumeus et al. (2001) used the linear stability analysis and demonstrated that a simple reaction-diffusion predator-prey model with a ratio-dependent functional response for the predator can lead to Turing structures due to diffusion-driven instabilities. 

Ebeling, W. On the possibility of diffusion instability in non-aqueous weak electrolytes. Z. Phys. Chem. (Leipzig), 1971, 247, p. 340-2. 

Thermal SN explosion mechanism was proposed by Colgate and White [32], In this picture, part of the neutrino flux liberated in the core collapse is deposited to the stellar mantle to make it unbound ( 1051 ergs is needed). Specific mechanisms include neutrino-driven fluid instabilities, for example convection both above neutrinosphere and inside the proto-NS. Neutrino-driven convection, however, may not be as important as thought before, as follows from recent detailed 2D studies of convection [24], Instead, other fluid instabilities such as newly found double-diffusive instability (the so-called lepto-entropy fingers ) [23], may effectively increase neutrino luminosity to help successful explosion. Note here that process ve -I u(, e1 I e —>7 + 7... 

Refiners and Schork used lauroyl peroxide as the initiator and also as the costabUizer, and found that diffusion instability was reduced to the point where nucleation in the monomer droplets and polymerization conld be carried ont before significant diffusional degradation of the droplets took place. Alduncin et al. compared different oil-solnble initiators in conjunction with hexadecane as the costabUizer, and fonnd that only lanroyl peroxide was water-insolnble enongh to stabilize the monomer droplets against degradation by molecnlar diffusion. ... 

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