Achieving a High Speed and Momentum Synthetic Jet Actuator
A detailed analysis of a finite span synthetic jet in a quiescent fluid is presented, with the goal of achieving a high speed and momentum synthetic jet, with a peak velocity exceeding 200 m/s. A total of two scales of actuator apparatuses having either 40 or 80 mm diameter piezoelectric discs were used. A temperature compensated hot wire, laser displacement sensor, and dynamic pressure transducers were used to quantify the performance of a given actuator. The synthetic jet generation process was divided into its main components, diaphragm displacement, cavity pressure, and orifice velocity, which were analyzed in detail in both their peak values and time responses. The phase shift between the disc displacement and velocity signals were found to be mainly attributed to compressibility effects. Doubling the diameter and thickness of the piezoelectric disc was found to double the output jet velocity and shift the operation frequency range of the system. In addition, a dual disc configuration was used, which yielded an approximately 40% higher jet velocity than its single disc configuration. Using the knowledge acquired from these experiments resulted in a synthetic jet having a peak velocity of 211 m/s out of a 12x1 mm rectangular orifice at 700 Hz, which is significantly stronger than any similar actuator reported in the literature.