Visualization of turbulent reactive jet by using direct numerical simulation

Direct numerical simulation (DNS) of turbulent planar jet with a second-order chemical reaction (A + B → R) is performed to investigate the processes of mixing and chemical reactions in spatially developing turbulent free shear flows. Reactant A is premixed into the jet flow, and reactant B is premixed into the ambient flow. DNS is performed at three different Damköhler numbers (Da = 0.1,1, and 10). Damköhler number is a ratio of a time scale of a flow to that of chemical reactions, and in this study, the large Da means a fast chemical reaction, and the small Da means a slow chemical reaction. The visualization of velocity field shows that the jet flow is developed by entraining the ambient fluid. The visualization of concentration of reactant A shows that concentration of reactant A for Da = 1 and 10 becomes very small in the downstream region because the chemical reaction consumes the reactants and reactant A is diffused with the jet development. By comparison of the profiles of chemical reaction rate and concentration of product R, it is found that product R for Da = 10 is produced by the chemical reaction at the interface between the jet and the ambient fluids and is diffused into the jet flow, whereas product R for Da = 0.1 is produced in the jet flow after reactants A and B are well mixed.