Toward Smart Control of Turbulent Jet Mixing and Combustion(<Special Issue>Jets, Wakes and Separated Flows)

Recent progress in active control of jet mixing and combustion is introduced. Miniature electromagnetic flap actuators are mounted on the periphery of an axisymmetric nozzle exit. It is demonstrated that even weak disturbances introduced into the initial shear layer by these actuators can significantly modify the large-scale vortical structures. This control technique is extended to the control of methane/air mixing and diffusion combustion by using a coaxial jet nozzle with the same flap actuators. As a result, the flame characteristics can be much improved in terms of stability and emission. Direct numerical simulation of a confined coaxial jet control has also been carried out. Although the distributed actuators are modeled somewhat ideally, DNS clearly demonstrates enormous effects of the present control scheme on the initial shear layer dynamics and concentration mixing.