Pattern analysis of viscous oscillation in a shear flow induced by an exothermic reaction

An investigation is made of oscillatory phenomenon induced by an exothermic reaction. This oscillatory phenomenon occurs in a very thin mixing layer between two miscible and reacting fluids. A qualitative model based on the interaction among reaction, molecular momentum transfer, molecular heat transfer, molecular mass transfer and forced convective transfer was proposed by Kuroda and Ogawa [1994. Nonlinear waves in a shear flow with a diffusive exothermic reaction and its qualitative reasoning. Chem. Eng. Sci. 49(16), 2699-2708]. It is experimentally shown in the present study that the oscillatory patterns change in the flow direction. In the upstream area where oscillatory patterns are nearly straight stripes, effects of viscosity on those stripes are investigated. In the downstream area where stripes are wavy and disordered, fractal analysis is introduced to investigate the relationship between the transition of oscillatory flow patterns and process factors, i.e. the viscosity ratio, the entire viscosity, flow rate and the flow rate ratio. Fractal analysis is also applied to temperature oscillation, and it is confirmed that the characteristic patterns of oscillation become obscure as the entire viscosity increases. The entire viscosity is an important factor for controlling both oscillatory patterns of flow and temperature in this reactive flow system. (c) 2007 The Japan Society of Fluid Mechanics and Elsevier B.V. All rights reserved.