HOW DOES THE PLACEMENT OF AN ACOUSTIC SOURCE INFLUENCE A DROP'S EVAPORATION?

The influence of the position of an acoustic source on an evaporating drop is investigated at various acoustic frequencies. Three positions are considered: at the bottom of the drop, at 45° with the vertical plane, and at one side. The evaporation and internal circulation are found to be maximum for the bottom position, intermediate for the inclined, and minimum for the side position for a given frequency. A lower frequency shows higher evaporation for a given position. The induced acoustic streaming at the drop's surroundings is visualized, and the corresponding outer flow is found to reduce for the higher frequencies. The flow is found to be highest and uniform for the bottom position. The flow is reduced for 45° position and is least for the side one. The flow is nonuniform for the inclined and side position. The streaming is thus weak in the two positions of the acoustic source. The outer flow induces shear on the drop's surface according to the source's position and causes the internal circulation to behave accordingly.