Measurements of macrosonic standing waves in oscillating closed cavities

Measurements of macrosonic standing waves in gases in oscillating closed cavities are shown. The strong dependence of the pressure waveform upon cavity shape is demonstrated. This dependence is exploited to provide control of harmonic phase and amplitude, thus avoiding shocks and enabling resonant waveforms to reach macrosonic pressures. The exploitation of this dependence is referred to as resonant macrosonic synthesis (RMS). Power is delivered to the cavity by oscillating it with a linear actuator (entire resonator drive). Standing wave overpressures in excess of 340% of ambient pressure are demonstrated in RMS cavities, compared to maximum overpressures of 17% observed in cylindrical resonators. Ratios of maximum to minimum pressures of 27 were observed in RMS cavities compared to 1.3 for cylinders. Measurements are shown for four axisymmetric cavity shapes: cylinder, cone, horn-cone hybrid, and bulb. Cavities were filled with nitrogen, propane, or refrigerant R-134a (1,1,1,2-tetrafluoroethane). Physic...