An Experimental Study of Fluidic Coupling Between Multiple Piezoelectric Fans

Piezoelectric fans have been shown to provide large enhancements in heat transfer over natural convection while consuming very little power. These fans consist of a piezoelectric material attached to a flexible cantilever. When driven at resonance, large oscillations at the cantilever tip cause fluid motion, which in turn, results in improved heat transfer rates. In this work, the performance of two fans operating simultaneously is analyzed. A coupling phenomenon is observed which, for a given input, causes an increase in vibration amplitude of as large as 40 percent compared to an isolated single fan. Understanding this coupling is essential in order to create design tools for implementing piezoelectric fans in practical cooling systems. Mylar fans are analyzed, and multiple experiments performed in air and within a vacuum chamber to isolate the source of coupling and determine its magnitude. The results suggest that coupling is almost entirely due to fluid-structure interaction, and the impact on the characteristic vibration parameters is explored. The collective motion of the fans decreases the fluidic damping, and the coupling magnitude is determined for a range of fan pitches