Acoustothermal Effect: Mechanism and Quantification of the Heat Source

Abstract

We examined theoretically, experimentally and numerically the origin of the acoustothermal effect using a standing surface acoustic wave actuated sessile water droplet system. Despite a wealth of experimental studies and a few recent theoretical explorations, a profound understanding of the acoustothermal mechanism remains elusive. This study bridges the existing knowledge gap by pinpointing the fundamental causes of acoustothermal heating. Theory broadly applicable to any acoustofluidic system at arbitrary Reynolds numbers going beyond the regular perturbation analysis is presented. Relevant parameters responsible for the phenomenon are identified and an exact closed form expression delineating the underlining mechanism is presented. Furthermore, an analogy between the acoustothermal effect and electromagnetic heating is drawn, thereby deepening understanding of the acoustothermal process.