A new experimental method based on volume measurement for determining axial scaling during breakup of drops and liquid threads

• Published in: Physics of fluids (1994) 2018-08, Vol.30 (8)
• Main Authors: Wagoner, Brayden W., Thete, Sumeet S., Basaran, Osman A.
• Format: Article
• Language: English
• Subjects: Breakup; Brownian motion; Experimental methods; Fluid dynamics; Newtonian liquids; Nozzles; Physics; Predictions; Scaling; Volume measurement
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.5030330

Thread breakup is ubiquitous in drop formation. As liquid threads thin, monitoring the time variation of the thread’s minimum radius hmin and the axial extent of the pinching zone z′ can help decipher the balance of forces governing breakup. The variation of hmin with time from pinch-off, τ ≡ tb − t (t is time; tb is breakup time)—radial scaling—can be determined experimentally from images of drops forming from a nozzle. Thus, all previous experimental studies report radial scaling, viz., hmin ∼ τa (a is the radial scaling exponent). Determination of axial scaling or how z′ varies with τ, z′ ∼ τb (b is the axial scaling exponent), however, is not as straightforward and hence rarely reported. Experimental determination of axial scaling is made difficult because thinning threads can be long and slender, and hence data on time evolution of z′ can be noisy. Moreover, inference of z′ from experiments can be challenging in situations involving suspension drops containing non-Brownian particles where particles can partially protrude out of the interface. We present a new way of determining axial scaling by experimental measurement of the time variation of the volume of the pinching zone and inferring z′ from volume measurements. The accuracy of the new method is tested by new experiments in which the scalings are determined during dripping of Newtonian liquids and are shown to be in excellent accord with scaling predictions and transitions between different regimes predicted from theory and simulation.