Schlieren Visualization and Analysis of Sweeping Jet Actuator Dynamics

Abstract

An innovative schlieren system design is introduced using two off-the-shelf telescopes instead of large, expensive lenses or mirrors. Schlieren is used in combination with a high-speed camera to investigate the internal dynamics of sweeping jet actuators. These devices are of particular interest due to their great success in active flow control applications for aerodynamic purposes. Their working principle based on schlieren images is discussed in detail based on a first model. An extended theory based on nondimensional frequency and jet velocity is introduced. A second model consisting of two adjacent sweeping jet actuators is investigated on their interaction characteristics by tracking their motion in the acquired schlieren images and the subsequent analysis of the relative deflection of the jets using fast Fourier transform, phase information, and the Hilbert transform. This is performed for multiple separation distances and two pressure ratios, leading to an underexpanded exit jet and a transonic jet. Last, the probability distribution of the deflection angles for both cases is discussed.

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