Ultimate fate of a dynamical bubble/droplet system following acoustic vaporization

Abstract

The phase-change of a liquid droplet induced by a supply of acoustic energy is known as “Acoustic Droplet Vaporization,” and it represents a versatile tool for medical applications. In an attempt to understand the complex mechanisms that drive the vaporization threshold, a theoretical concentric three phase model (bubble of vapor dodecafluoropentane + layer of liquid dodecafluoropentane + water) is used to compute numerical simulations of the vapor bubble time evolution. The dynamics are sorted into different regimes depending on their shared characteristic and the system ultimate fate. Those regimes are then organized within a phase diagram that collects all the possible dynamics and that predicts whether the complete vaporization occurs or not.

Numerical investigation of acoustic vaporization threshold of microdroplets

“…The acoustic amplitude increased to causes complete vaporization after multiple bubble oscillations, but a higher amplitude of causes irreversible bubble collapse after multiple rebounds. This indicates that the ADV becomes more complicated under high frequency conditions and the bubble growth regimes 2 and 3 are not clearly distinguished by the acoustic amplitude, which was also observed by Lacour et al [27] . The complete vaporization occurs in the acoustic amplitude range of , as depicted in Fig.…”

“…The minimum pressure for direct droplet vaporization without any collapse and rebound is called the direct threshold in Refs. [23] , [27] . This bubble growth regime was observed by Li et al [34] while visualizing the formation of toroidal bubbles from high acoustic pressure.…”

“…(23) has an advantage in preserving the bubble mass over Eq. (26) used in many previous studies [21] , [22] , [23] , [27] , which can be derived from Eq. (23) and the thermodynamic relation in the isentropic process.…”

“…The initial bubble radius is unknown and can be considered an external parameter. In this work, we choose as a base case, which was also used by Lacour et al [23] , [27] while predicting the ADV threshold of DDFP droplets.…”

“… [24] , [25] , [26] that it can use a very fine mesh needed for the calculation of the initial bubble nucleus. Recently, Lacour et al [27] applied the RP based numerical model to investigate the ultimate fate of a DDFP bubble nucleus forming in a DDFP droplet and determine the ADV threshold in various acoustic frequencies. The bubble growth pattern is observed to have three regimes: irreversible collapse without growth (regime I), direct vaporization without rebound (III) and intermediate behavior with collapses, rebounds and oscillations (regime II).…”