Numerical Simulations of Competitive-Consecutive Reactions in Turbulent Channel Flow

This thesis deals with mixing of passive scalars in a turbulent flow. The passive scalars are released in a turbulent plane channel flow and interpreted as either non-reactive components or reactive components that are involved in a competitive-consecutive reaction system. The evolution of these passive scalars under influence of turbulent mixing and chemical reaction is studied by means of Direct Numerical Simulation (DNS). For the non-reactive case, the mixing process behind two parallel line sources placed at a short distance from each other is studied and in particular the interference in the concentration statistics. The results of this study are interpreted as the concentration statistics resulting from two nearby stacks that release into the atmospheric boundary layer. For the reactive components, we study the downstream situation behind a source of species B placed in a background concentration of species A, where A and B are involved in the reaction system A+B => R, R+B => S and R is considered to be the desired reaction product. The rate of both reactions is determined by the combined influence of turbulent mixing and chemical kinetics. The primary influence on the course of this reaction system is found to be the hydrodynamics. The large scale turbulent fluctuations suppress the rate of the first reaction and enhance the rate of the second reaction. This effect could be an explanation for the anomalous high yields of S that are sometimes observed in experiments