Exploitation of Higher-Order Membrane Modes for Improved Synthetic Jet Performance

摘要

Electroactive polymer synthetic jets (E-jets) are a new lightweight low-power means of generating a synthetic jet for low-speed active flow control applications. The actuation method uses a thin (≈i30 μm) prestrained low modulus and a circular-composite-dielectric acrylic elastomer membrane. The membrane is excited to operate at transverse resonance to pump air in and out of a partially closed chamber. Based on device configurations experimentally tested to date, the attainable nozzle velocity has been determined to be greater than 25 m/s at a nozzle exit diameter of 13 mm and a frequency of approximately 250 Hz without optimization. While performing device frequency sweep characterization, it was noted that certain higher membrane vibration modes induced significantly greater jet velocities than the fundamental membrane mode. A series of tests was performed using a stroboscope to identify the modes and correlate them qualitatively with device performance. These tests verified the presence of classical membrane modes. A second series of tests was then performed using a scanning laser vibrometer to quantitatively correlate membrane mode shapes with device performance. The vibrometer tests experimentally attributed peak velocity performance to the presence of one particular nonclassical higher-order mode. The exploitation of coupled higher-order membrane modes for increased synthetic jet performance represents a new operating paradigm for similar classes of systems.