Computational characterization on the thermoacoustic thermophone effects induced by micro/nano-heating elements

Abstract

A thermoacoustic thermophone is a classical device wherein an alternating current passes through a thin heating element to emit sound. The newly emerging micro- and nanotechnology has not only greatly improved such a device’s performance, but also expended its new potential functions such as serving as directional ultrasound sources, phased arrays, or even in some audible sound applications. So far, most investigations on thermoacoustic thermophones are on experimental parts. Besides, the existing theoretic analysis generally adopted a fundamental equation for characterizing the surrounding gas which unfortunately could only consider the heat conduction effect. However, the transient volume and pressure change in an ideal gas caused by the periodic heating would definitely trigger the flow process, which in fact contributed to most of the phenomena occurring in small scale. Here, to disclose the actual working process of the thermoacoustic thermophone and the mechanisms thus involved, we developed a computational model to systematically describe both the gas flow dynamics and heat transfer behavior for the first time. Some important physical parameter variations initiated by the alternating voltage and the corresponding double frequency heat flux, such as pressure, velocity, temperature, etc., were successfully revealed. Discoveries on such variations paved the way for the identification of critical factors that affected the sound pressure, which as a result would serve as a valuable reference for designing a thermoacoustic thermophone in the near future.