Control of Cavity Oscillations in a Supersonic Flow by Microjet Injection

The control of oscillations in a supersonic cavity flow is pertinent to internal weapons bays and has also recently gained attention due to the possible use of cavities for flame stabilization in scramjet (Supersonic Combustion Ramjet) combustors. The transducers have a diameter of 5.54 mm and were flush mounted on the cavity walls. The signal from the transducer was passed through a signal conditioner and fed to a computer through a 12 bit analog to-digital data acquisition card (NI PCI- 6024E) with a maximum sampling rate of 200 kHz. The signal from each transducer was acquired in differential mode and sampled at 100 kHz for 0.5 s, giving 50,000 samples of unsteady pressure data. These samples were then filtered in the range of 500 25,000 Hz using high-pass and low-pass digital filters, respectively, because the dominant frequencies lie well within this range. In all experiments, the two transducers have been used to acquire the signals simultaneously.