Large eddy simulation predictions of mixing enhancement for jets in cross-flows

Abstract

The efficiency of a set of mixing enhancement devices on an array of jets in cross-flow is studied using large eddy simulation (LES). The baseline flow is a rectangular channel flow on which five jets in cross-flows are installed on each wall (upper and lower). Mixing devices are fixed tabs installed upstream of the jets. Instantaneous analyses of the LES fields reveal two large vortical structures developing downstream of the mixing device. These structures strongly enhance mixing. Comparisons of the statistically averaged LES predictions against experimental results validate the predictions. The mixing devices provide a better spatial and temporal homogeneity of the gas mixture at the exit of the main duct. Even though full temporal and spatial homogeneity of the gas mixture prior to combustion is not guaranteed with this design, the probability of finding strong inhomogeneous zones is reduced. More generally, this study confirms the power of LES to help design actuating devices for flow and mixing control.