Open- and Closed-Loop Control of a Turbulent Round Jet Based on Fluidic Means

Abstract

This work investigates experimentally active control of an air round jet using radial unsteady air microjets. Two microjets were placed at diametrically opposite locations upstream of the nozzle exit. The Reynolds number was 8,000. The flow was measured in two orthogonal diametrical planes using various techniques. Under the open-loop control, the jet centreline decay rate K exhibits a strong dependence on the mass flow ratio C _m of microjets to the primary jet and excitation frequency ratio f _e /f ₀ of microjets, where f _e is the microjet excitation frequency and f ₀ the preferred mode frequency of the uncontrolled jet. A closed-loop control technique has been developed to achieve automatically and rapidly the optimal control performance and the maximum K, as obtained from the open-loop control.