Continued self-similar breakup of drops in viscous continuous phase in agitated vessels (original) (raw)
Related papers
Effect of Dispersed-Phase Viscosity on the Maximum Stable Drop Size for Breakup in Turbulent Flow
Journal of Chemical Engineering of Japan, 1977
A formula for the maximumstable drop size has been derived theoretically, by taking into consideration the effect of the dispersed-phase viscosity. The derived formula indicates that the controlling factors of the maximumstable drop size are the WeberNumberand the viscosity group which is defined as the ratio of the viscous stress to the stress of interfacial tension. The validity of the formula was confirmed experimentally over a wide range of dispersed-phase viscosity.
A model of droplet breakup in a turbulent flow for a high dispersed phase holdup
h i g h l i g h t s A model of droplet breakup at a high dispersed phase holdup is developed. Droplet fluctuation velocities are calculated by kinetic theory of granular media. The breakup model developed is incorporated into the STARCCM+ Ò CFD code. The breakup model is validated using experimental data obtained in a Couette device.
Journal of Dispersion Science and Technology, 2005
The breakage of drops or bubbles in isotropic turbulent dispersions has been investigated. Based on the experimental data given in the literature, some new empirical relationships are derived to evaluate the minimum stable drop sizes, the breakup frequencies, and the drop size distribution in turbulent dispersions. The solutions of the stochastic Focker‐Planck equation are used to estimate the particle size
Effect of turbulence on drop breakup in counter air flow
International Journal of Multiphase Flow, 2019
Understanding the factors that lead to breakup of liquid droplets is of interest in many applications. Liquid droplet breakup processes are typically broken into regimes based on a Weber number calculated based on an average flow velocity (Solsvik et al., 2013). In turbulent flows, the instantaneous velocity may differ significantly from the average velocity. Here an experimental investigation on the role of turbulence in the breakup process is undertaken, whose continuous phase is gas. The turbulence is produced by confined counterflow into which the droplets fall. Droplet breakup mode is visualized by high speed camera, and the turbulence of counterflow is measured by Particle Image Velocimetry. The experimental results show that the breakup morphology and mode frequency varies with the turbulence intensity of the counterflow.
Droplet breakup mechanisms: Stepwise equilibrium versus transient dispersion
Journal of Rheology, 1993
In dispersive mixing of immiscible liquids the minimum attainable dropsize is often deduced from the critical value of the Capillary number (the ratio of the shear stress to the interfacial stress) necessary for drop breakup under quasiequilibrium conditions. The critical Capillary number shows a minimum if the viscosity ratio between dispersed and continuous phase is about one. Hence, it is commonly accepted that the finest morphology is obtained if both viscosities match. In practical mixing devices, however, small drops are formed by a transient mechanism of thread breakup during extension rather than by stepwise breakup under equilibrium conditions. For Newtonian liquids, a comparison is made between the dropsizes resulting from a stepwise equilibrium and a transient breakup mechanism. Generally, the transient mechanism yields smaller drops and, more interestingly, a higher viscosity ratio between the dispersed and continuous phases results in a finer morphology, as already indicated by . In the present paper the comparison is elaborated over a broad range of the relevant parameters while a compact illustrative presentation of the results is given to stress the possible consequences for practical blend morphologies.
Drop breakup in turbulent stirred-tank contactors. Part I: Effect of dispersed-phase viscosity
AIChE Journal, 1986
Numerous experiments were conducted in four, baffled cylindrical tanks of standard geometry, equipped with six-blade Rushton turbines, by photographically examining dilute suspensions of silicone oils in water. Five grades of oil, ranging in viscosity from about 0.1 to 10 Pas and exhibiting the same interfacial tension with water ([0.0378 N / m), were employed. The range of variables studied includes 13,000 < Re < 101.000. 44 < We < 1.137, and 0.065 < < 0.50 m2/s3. The objectives of the experimental program were to examine the extent to which dispersed-phase viscosity influences equilibrium mean drop size and drop size distribution at constant interfacial tension, and to determine the relevance of the predicted correlating parameters and the range of applicability of the semiempirical theory.
Breakup time and morphology of drops and bubbles in a high-Reynolds-number flow
Journal of Fluid Mechanics, 2006
The breakup process of a drop or a bubble immersed in a straining flow at high Reynolds numbers, is studied numerically with the aim at comparing the breakup frequencies obtained with those measured in real flows. We assume that both the inner and the outer velocity fields are axisymmetric and irrotational. Under these assumptions the time evolution of the drop's interface is computed with a boundary integral method for a wide range of the inner-to-outer density ratios, Λ. Despite the simplicity of the model, it qualitatively displays some of the features of the turbulent breakup of drops and bubbles observed experimentally. Furthermore, when Λ ∼ O(1), the slender geometry of the droplets observed in the numerical simulations suggests the use of a simplified theoretical analysis that reproduces accurately the time evolution of the drop radius obtained numerically.