Shock induced aerobreakup of a polymeric droplet

Abstract

Droplet atomization through aerobreakup is omnipresent in various natural and industrial processes. Atomization of Newtonian droplets is a well-studied area; however, non-Newtonian droplets have received less attention despite their frequent encounters. By subjecting polymeric droplets of different concentration to the induced airflow behind a moving shock wave, we explore the role of elasticity in modulating the aerobreakup of viscoelastic droplets. Three distinct modes of aerobreakup are identified for a wide range of Weber number (∼ 10 2 − 10 4 ) and Elasticity number (∼ 10 −4 − 10 2 ) variation; these modes are-vibrational, shear-induced entrainment and catastrophic breakup mode. Each mode is described as a three stage process. Stage-I is the droplet deformation, stage-II is the appearance and growth of hydrodynamic instabilities, and stage-III is the evolution of liquid mass morphology. It is observed that elasticity plays an insignificant role in the first two stages, but a dominant role in the final stage. The results are described with the support of adequate mathematical analysis.

Depth from defocus technique applied to unsteady shock-drop secondary atomization

“…The fragmentation of this liquid sheet accounts primarily for the generation of secondary droplets, whose size distribution is being measured in the present work. The mechanistic insights into the droplet breakup through SIE mode can be found in Sharma et al (2021) and Chandra et al (2022) and is not the focus of present work. Figure 2a, b shows the global overview of interaction dynamics for Weber number values of 879 and 4088, respectively.…”

“…A detailed description of the experimental setup used for achieving shock-drop interaction can be found in previous work (Chandra et al 2022;Sharma et al 2021Sharma et al , 2022; however, the essential details of the test facility are also described here. The arrangement of equipment in a shock-droplet interaction setup is shown in Fig.…”

“…3. The global observation of the interaction phenomenon is obtained by using the experimental arrangement mentioned in previous work (Chandra et al 2022). A sample observation of the global view of interaction phenomenon for We ∼ 900 and 4000 is shown below in Fig.…”

“…2. The global observations are also utilized for measuring shock Mach number ( M s ) and Weber numbers (We) (Sharma et al 2021;Chandra et al 2022). Different values of the shock Mach number ( M s = 1.27, 1.39 and 1.56) and Weber number ( We ∼ 900, 2000 and 4000) are achieved by changing the electrical energy input to the exploding wire, while the diameter of the levitated drop was left unchanged.…”

Sub-Newtonian coalescence in polymeric fluids

“…In order to stretch the polymer chains, it is not only essential to have high strain rates but also accumulations of strains. 38,39 This indicates that polymeric fluids may behave as Newtonian fluids if the strains are smaller at early time scales. For coalescence, such observations are reported by Chen et al, 14 which is also reported by Dekker et al 20 However, our discussion is for a later timescale where the elasticity effects are predominant.…”