Bicomponent Drop's Evaporation: Effect of Acoustics and Hot Surrounding

The effect of acoustic streaming on the circulation inside methanol-water drops evaporating in a heated environment is examined. The circulation and the evaporation of drops for various acoustic frequencies with added white noise are recorded at varied surrounding temperatures (TS). Visualization reveals intense streaming at the drop's immediate vicinity at a lower frequency and elevated TS. The streaming velocity rises with (i) the reduction in acoustic frequency at a given TS and (ii) the escalation in TS at a given frequency. The drop's internal circulation is detected to be oscillatory, and the oscillation frequency reduces drastically with the temperature rise at the lowest acoustic frequency. Taken together, the higher streaming at a low acoustic frequency and elevated TS lead to higher air entrainment into the drop interior and quicken circulation by suppressing its oscillation. Thus, a greater mass is swept around the drop, causing an enhancement of the evaporation rate with TS.