Flow oscillation characteristics in conical cavity with multiple disks

This paper reports an experimental study on flow oscillation characteristics of an aerodynamic control device that we have proposed. The device can achieve an enhancement of the aerodynamic control ability and a reduction of the flow instability by adding multiple stabilizer disks to a conventional aerospike so as to divide the flow separation region into multiple cavities. In this device, several axisymmetric cavities are formed. It is well known that pressure oscillation is induced around cavities. In this study, the characteristics of the pressure oscillation of several cavities on a cone surface were investigated experimentally by unsteady pressure measurements in a wind tunnel testing. The conical-cavity pressure oscillation had a feature that the oscillation level is large in case that a length-to-depth ratio of the cavity is large; the oscillation frequency can be predicted by the famous Rossiter formula, which is reported in many previous researches on a single rectangular cavity. It was also found that adding thin disks into the large cavity is effective in the reduction of the pressure oscillation level downstream of the cavities. In addition, disk structural vibration measurements were conducted simultaneously with the unsteady pressure measurements, revealing that a flutterlike vibration could occur when the pressure oscillation frequency agrees with the disk eigenfrequency.