In this paper, we experimentally verify a new model of the acoustic oscillation that is observed in supersonic flows over a rectangular cavity. This model was developed previously in order to understand why the jump in the predominant oscillation frequency occurred when the length-to-depth ratio of the cavity was gradually varied. In the present experiment, the target flows are supersonic flows over a rectangular cavity of variable length-to-depth ratios. The inlet Mach number is selected to be 1.65. The length-to-depth ratio of the cavity is varied by changing the depth as the length remains constant. The pressure oscillation is measured by the semiconductor type pressure sensor mounted on the wall downstream of the trailing edge of the cavity, and the predominant frequencies are obtained experimentally for each length-to-depth ratio. Also, the predominant frequencies are calculated by using the model. The results obtained by using the model are found to agree with the experimental results with respect to both the frequency jump and the variation in frequency with the length-to-depth ratio.

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