Analysis and modelling of the effective reaction rate in a developing mixing layer

Simulations of the chemically reacting mixing layer were performed. Especially the early stage of the flow transition, when the coherent Kelvin-Helmholtz vortices can be recognized, was studied. This is a physical problem of great importance in many industrial and environmental systems. Simple passive reaction of the second order is considered. Its effective rate is analysed for different values of the Damköhler number. The results are compared to the case of the steady, laminar shear flow. It is found that slow and fast reactions respond in different ways to the fluctuations of the reactant concentration. Faster reactions appeared to be much more sensitive to the character of mixing. Moreover a buffer layer of product of fast reactions forms in the system and separates the substrates what influence the effective reaction rate.