Twin bi-component drops' evaporation in an acoustic field: The amplitude influence

The study explores twin bi-component drop evaporation at various acoustic frequencies and amplitudes. The drops have a fixed central spacing. The acoustic streaming around the drops varies with frequency and amplitude. The streaming rises with the amplitude at a given frequency. The acoustics push the outer flow away from the drop. Furthermore, the flow transforms from horizontal to vertical at higher amplitudes, indicating a rise in the outer flow. Correspondingly, the drops' internal circulation and evaporation rise. The maximum evaporation is observed at higher amplitudes and lower frequencies due to intense streaming. The intense streaming accelerates the circulation, forcing the oscillatory circulation to be steadier. In contrast, the circulation is unsteady for lower amplitudes and higher frequencies. The steady circulation escalates the convective current inside the drops and boosts the evaporation rate. An empirical expression is developed to predict the outer flow velocity and evaporation rate at various amplitudes for any twin bi-component drops under diverse acoustic conditions. The study's novelty lies in demonstrating how the amplitude plays a crucial role in modifying the outer flow and internal circulation to elevate the evaporation rate despite frequency.