59 research outputs found
Dissipation Scale Fluctuations and Chemical Reaction Rates in Turbulent Flows
Small separation between reactants, not exceeding , is the
necessary condition for various chemical reactions. It is shown that random
advection and stretching by turbulence leads to formation of scalar-enriched
sheets of {\it strongly fluctuating thickness} . The molecular-level
mixing is achieved by diffusion across these sheets (interfaces) separating the
reactants. Since diffusion time scale is , the
knowledge of probability density is crucial for evaluation of
chemical reaction rates. In this paper we derive the probability density
and predict a transition in the reaction rate behavior from
() to the high-Re asymptotics . The theory leads to an approximate universality of
transitional Reynolds number . It is also shown that if
chemical reaction involves short-lived reactants, very strong anomalous
fluctuations of the length-scale may lead to non-negligibly small
reaction rates
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