Abstract
Non-circular jets impinging on open-closed type cylindrical cavity are investigated. Five different orifice shapes, namely, circle, ellipse, rectangle, square, and triangle, are used to produce under-expanded jets. For a given orifice shape, experiments were done at four different Nozzle Pressure Ratios (NPRs), 3 to 4.5 in steps of 0.5. The Sound Pressure Level (SPL), the Overall Sound Pressure Level (OASPL) and the pressure inside the cavity are also monitored. In addition, the corresponding high-speed schlieren images are acquired. Circular orifice jet and cylindrical cavity combination emitted the highest noise levels. These devices produced tonal sounds around 130 dB. At low NPRs, there was not much difference in the performance of the Hartmann whistle for different shaped jets. However, at high NPRs, a substantial dip in OASPL value was found at the vertex compared to the span of different shaped orifice jets (rectangle, square, and triangle).
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