Detachment and attachment of an axisymmetric non-reactive jet with turbulent shear layer: Control by plasma actuator

Abstract

The control of an axisymmetric air jet equipped with a small-angle diffuser exhaust using a single non-thermal plasma actuator is studied with a stereoscopic PIV system. A single Dielectric Barrier Discharge (DBD) actuator is used to separate a naturally attached flow (12° angle diffuser) or to reattach a naturally separated one (22° angle diffuser). The experimental set-up allows us to measure the flow modifications occurring at the bevel of the diffuser. The actuator can generate a local flow (electric wind) of 6 m s −1 used to modify an axisymmetric air jet with centreline velocities of 10, 20 and 30 m s −1. The flow modifications under actuation are investigated in terms of time-averaged, phased-averaged fields as well as eddy localization. The analysis is mainly focused on the lower primary jet velocity at which the actuator presents a high efficiency. The results highlight that a plasma actuator can force the flow separation or attachment in a few dozen of milliseconds and that this device can be effective to manipulate the coherent structures surrounding the potential core. The global conclusion of the present study is that a single DBD actuator could be an effective device to promote the vortex shedding at the diffuser lip of an axisymmetric air jet. This may results in an improvement of the mixing characteristics, at least in the near-field region.