Turbulent flow and scalar mixing of a coaxial injector having two fluid jets

The turbulent flow and scalar mixing in a coaxial injector having two fluid jets were investigated by using large eddy simulation (LES). Several recess lengths, which are the retracted distance of the inner jet in a coaxial injector, were considered to analyze the geometric effects on the scalar mixing for nonreacting variable-density flows at a constant Reynolds number. The LES results showed the detailed description of flow structures and the changes of turbulent fluctuations caused by the recess. The flow structures in the near field of the injection plane were modified by the recess. When the inner jet was recessed, the development of turbulent kinetic energy became faster than that of the nonrecessed case. Also, it was found that a combination of outer-inner jets with a large density difference is better to complete the flow mixing within shortened streamwise length.