Morphological classification of low viscosity drop bag breakup in a continuous air jet stream

Abstract

To investigate the effect of Rayleigh–Taylor wave number in the region of maximum cross stream dimension (NRT) on drop breakup morphology, the breakup properties of accelerating low viscosity liquid drops (water and ethanol drops, diameter=1.2–6.6 mm, Weber number=10–80) were investigated using high-speed digital photography. The results of morphological analysis show a good correlation of the observed breakup type with NRT; bag breakup occurred when NRT was 1/3−1, bag-stamen breakup at 1–2, and dual-bag breakup at 2–3. The number of nodes in bag breakup, bag-stamen breakup, and dual-bag breakup all increased with Weber number. The experimental results are consistent with the model estimates and in good agreement with those reported in the literature.

Secondary breakup of a drop at moderate Weber numbers

“…where L rim is the length of the rim [48,51]. This suggests that, in the bag-breakup regime, typical number of nodes expected range from one to four.…”

“…Once the bag starts forming the rim starts to draw in more liquid as seen in the images (figure 4f -h) and acts as a support to the bag. Zhao et al [48] argued that the bag formation occurs when D max is larger than the critical RTI wavelength, λ c . The most dominant wavelength of RTI is given by [52],…”

“…Using the position of the centroids at different time instances, the acceleration of the droplet just before the initiation of bag formation can be estimated [48]. A nondimensionalized RTI wavenumber, given by K = D max /λ max , takes values between 1/ √ 3-1 for bag breakup regime [48].…”

“…Using the position of the centroids at different time instances, the acceleration of the droplet just before the initiation of bag formation can be estimated [48]. A nondimensionalized RTI wavenumber, given by K = D max /λ max , takes values between 1/ √ 3-1 for bag breakup regime [48]. In our simulations, the value of K for the case of We = 20 is 0.988 which agrees well with the experimental observations of Zhao et al [48].…”

“…A nondimensionalized RTI wavenumber, given by K = D max /λ max , takes values between 1/ √ 3-1 for bag breakup regime [48]. In our simulations, the value of K for the case of We = 20 is 0.988 which agrees well with the experimental observations of Zhao et al [48]. We note here that for sheets (flattened drop here) the finite thickness affects the critical and the dominant mode of Taylor instability (see [53]).…”