Flow Manipulation by Standing Acoustic Waves and Visualization with Background Oriented Schlieren (BOS)

In this work, a novel approach for flow manipulation by standing acoustic waves is presented. A phased array of ultrasonic transducers operating at 40 kHz is used to generate acoustic waves of various patterns. The interaction of these wave patterns with a thermally induced air flow (thermal convection) is evaluated. The Background Oriented Schlieren method (BOS) in combination with a thermal “contrast medium” allowed a clear visualization of the effects. The final images were generated from the raw data by applying an easy to implement pixel-by-pixel difference method.