An experimental study of Mesler entrainment on a surfactant‐covered interface: The effect of drop shape and Weber number

Abstract

Mesler entrainment is the formation of large numbers of small bubbles which occurs when a drop strikes a liquid reservoir at a relatively low velocity. Existing studies of Mesler entrainment have focused almost exclusively on water as the working fluid in a nominally clean state, where even very small levels of contamination can cause significant changes in surface tension that affect the repeatability of the results. Herein water combined with the soluble surfactant Triton X-100 is used as the working fluid in an attempt to stabilize the state of the water surface. Despite this approach, nominally identical drops did not always result in the same bubble formation event. Accordingly, Mesler entrainment was quantified by its frequency of occurrence for drops having the same nominal diameter and impact velocity. This frequency of occurrence was found to be well correlated to both the Weber number and the shape of the drop on impact. V

Micro-bubble morphologies following drop impacts onto a pool surface

“…These internal drop dynamics can explain the large central bubble appearing in some of the earlier studies, e.g. figure 7(a) in Mills et al (2012).…”

“…The edge moves much more rapidly up away from the ruptures, again suggesting a significantly thinner air layer along the sides. Similar formation of multiple holes along a ring may explain the bubble chandeliers observed in water (Sigler & Mesler 1990;Liow & Cole 2007;Mills et al 2012). Thoroddsen, M.-J.…”

“…Thoraval, K. Takehara and T. G Thoroddsen, Etoh & Takehara (2003) imaged detailed dynamics of the entrapment of a central bubble, along with a handful of realizations for film breakup for water drops. However, Mills, Saylor & Testik (2012) showed convincingly that the water case suffers from highly random film ruptures and is not repeatable, even if surfactants are included. Recently, Saylor & Bounds (2012) have shown that air film formation and breakup are much more repeatable for silicone oils than for water.…”

Antibubbles and fine cylindrical sheets of air

“…Beilharz and others frequently named Mesler entrainment (Sigler & Mesler 1990). Mills, Saylor & Testik (2012) showed that the breakup of this air layer is inherently random for water, while Saylor & Bounds (2012) demonstrated that the thin air films are much more stable for some other liquids, such as silicone oils and ethanol (Sundberg-Anderson & Saylor 2014). This repeatability allowed Thoroddsen et al (2012) to study details of the air-film breakup, employing triggered imaging with an ultra-high-speed CCD video camera (Etoh, Poggemann & Kreider 2003).…”

Do we understand the bubble formation by a single drop impacting upon liquid surface?

“…The Mesler entrainment region is characterized by a number of tiny air bubbles with diameters that are 50 μm or less. 8,[12][13][14][15] Recently, it was found that daughter bubbles cascaded from the rupture of huge floating bubbles 16 can also contribute to the generation of small bubbles that are less than 1 mm. This greatly enhances the dissolution rate of gas into a liquid pool (owing to the high pressure within the tiny bubbles) and also closely tied to the climate considering aerosol droplets that form from bursting of huge bubbles.…”