An experimental study of transient effects in the breakup of viscous drops

Stone, Howard A.; Bentley, B. J.; Leal, L. Gary

doi:10.1017/s0022112086001118

Cited by 395 publications

(273 citation statements)

References 27 publications

Supporting

Mentioning

233

Contrasting

Unclassified

Order By: Relevance

“…Subsequently, the droplet attains a dumbbell-like shape before becoming an ellipsoid. This type of relaxation, consisting of an initial relaxation by means of a shape change without significant reduction of the droplet length, followed by a simple droplet retraction, was reported on by several authors (Stone et al (1986) (2009)). In those studies, the highly deformed non-ellipsoidal droplet shape was however generated by applying flow with a supercritical Ca rather than confining the droplet between parallel plates.…”

supporting

confidence: 55%

Droplet relaxation in blends with one viscoelastic component: bulk and confined conditions

Cardinaels

Moldenaers

2010

Rheol Acta

View full text Add to dashboard Cite

Using a counter rotating parallel plate shear flow cell, the shape relaxation of deformed droplets in a quiescent matrix is studied microscopically. Both the effects of geometrical confinement and component viscoelasticity are systematically explored at viscosity ratios of 0.45 and 1.5. The flow conditions are varied from a rather low to a nearly critical Ca-number. Under all conditions investigated, viscoelasticity of the droplet phase has no influence on shape relaxation, whereas matrix viscoelasticity and geometrical confinement result in a slower droplet retraction. Up to high confinement ratios, the relaxation curves for ellipsoidal droplets can be superposed onto a master curve. Confined droplets with a sigmoidal shape relax in two stages; the first consists of a shape change to an ellipsoid with a limited amount of retraction, the second is the retraction of this ellipsoid. The latter can be

show abstract

supporting

confidence: 55%

Droplet relaxation in blends with one viscoelastic component: bulk and confined conditions

Cardinaels

Moldenaers

2010

Rheol Acta

View full text Add to dashboard Cite

show abstract

“…The viscosity ratios we tested ( 1.5 to 4.1) may not vary enough to have an impact on ⁄ . For a free drop submitted to shear, Stone et al 28 found that breakup occurs above a critical elongation ratio, function of but for 0.1 to 1, the critical elongation ratio did not vary significantly. Similarly, we find Oh from 1.7×10 -2 to 5.3×10 -2 .…”

Section: B Critical Elongation Ratiomentioning

confidence: 99%

Drop generation from a vibrating nozzle in an immiscible liquid-liquid system

et al. 2016

View full text Add to dashboard Cite

Drop generation from an axially vibrating nozzle exhibits a transition in drop diameter when varying the vibration amplitude. Below a threshold amplitude, forcing has essentially no effect on drop size and drops form in dripping mode. Above the threshold, drop size is controlled by forcing: drops detach at resonance, i.e., when the first eigenfrequency of the growing drop coincides with the forcing frequency. We experimentally study the impact of the nozzle inner diameter, dispersed phase flow rate, interfacial tension, and dispersed phase viscosity on this transition. Drop diameter is well correlated to the mode 1 eigenfrequency of Strani and Sabetta for a drop in partial contact with a spherical bowl. We propose a transient model to describe drop dynamics until detachment. The drop is modelled as a linearly forced harmonic oscillator, with the eigenfrequency of Strani and Sabetta. Since the dispersed phase does not wet the nozzle tip, an additional damping coefficient is introduced to account for the viscous dissipation in the film of continuous phase between the drop and nozzle surface. The model adequately reproduces the effect of the different parameters on the threshold amplitude.

show abstract

“…Several methods to investigate the droplet deformation and break-up under laminar conditions are established, experimentally e.g., in a four-roller mill [16,[51][52][53][54][55][56][57] or by modelling and numerical simulation [56,[58][59][60][61], respectively. Analysing the resulting DSD as a function of deforming stresses and material properties, especially viscosity ratio, allowed several authors to correlate the droplet break-up with the dimensionless Capillary number Ca.…”

Section: Why Do We Need Detailed Information On the Hph Process?mentioning

confidence: 99%

Optical Measuring Methods for the Investigation of High-Pressure Homogenisation

Bisten

Schuchmann

2016

Processes

View full text Add to dashboard Cite

High-pressure homogenisation is a commonly used technique to produce emulsions with droplets in the micro to nano scale. Due to the flow field in the homogenizer, stresses are transferred to the interface between droplets and continuous phase. Cohesive forces within droplets interact with external stresses. To exceed the cohesive forces, high process pressures are necessary, which might cause a complex flow pattern and large flow velocities. Additionally, the pressure drop can induce cavitation. Inline measurements are a challenge, but necessary to understand droplet break-up in a high-pressure homogenizer. Recently, different optical methods have been used to investigate the flow conditions as well as the droplet deformation and break-up in high-pressure homogenisation, such as high speed imaging, particle and micro particle image velocimetry. In this review, those optical measuring methods are considered critically in their applications and limitations, achievable results and further developments.Keywords: high-pressure homogenisation; optical measurement methods; flow field characterisation; droplet break-up; emulsification MotivationHigh-pressure homogenisation (HPH) is widely used in chemical, pharmaceutical and food industry to produce emulsions with desired properties. Properties of emulsions, like mouth feel, colour, flow behaviour, or stability, depend strongly on their microstructure and thus on the droplet size distribution of the emulsion [1]. However, tailor-made adjustments of the droplet size distribution in emulsions is still challenging due to complexity of interactions of the process conditions and the properties of the formulation. In order to decrease the droplet size distributions, the volume-related energy density E v is increased, most often by increasing the pressure drop ∆p in the disruption unit [2]. Unfortunately, this might also lead to cavitation and cavitation-induced wear at the devices. A change in the homogeniser disruption unit design may also improve droplet breakup. As an example, Microfluidics ® offers so-called T-or Z-shaped disruption units which allow droplet size reduction well below <1 µm for specific formulations. Other manufacturers merchandise specific "energy-efficient" disruption units. Even when these disruption units work fine with some formulations, they do not with others. A deep understanding in the influence of disruption unit design and process parameters on flow patterns and resulting droplet sizes is still missing.One possibility to describe the influence of process conditions, and/or product recipe on resulting droplet sizes is to measure the average droplet size or the droplet size distribution (DSD) of the emulsion after homogenisation. Thus, the influence of different parameters like pressure drop [2][3][4][5], geometry of the device [2,6-9], or formulation [10][11][12][13] can be related to homogenisation efficiency, which allows some mechanistic insight into the high-pressure homogenisation process. However, offline measurements always repre...

show abstract

An experimental study of transient effects in the breakup of viscous drops

Cited by 395 publications

References 27 publications

Droplet relaxation in blends with one viscoelastic component: bulk and confined conditions

Droplet relaxation in blends with one viscoelastic component: bulk and confined conditions

Drop generation from a vibrating nozzle in an immiscible liquid-liquid system

Optical Measuring Methods for the Investigation of High-Pressure Homogenisation

Contact Info

Product

Resources

About