scholarly journals Breakup of Droplets in Micro and Nanofluidic T-Junctions

2011 ◽  
Vol 110-116 ◽  
pp. 3673-3678
Author(s):  
Ahmad Bedram ◽  
Ali Moosavi
Keyword(s):  
Optimum Condition ◽  
Numerical Simulations ◽  
Capillary Number ◽  
Volume Of Fluid ◽  
Vof Method ◽  
Large Droplet ◽  
Micro Scale ◽  
Breakup Length ◽  
Breakup Time

We employ numerical simulations to investigate the breakup of droplets in micro-and nanoscale T junctions which are used to produce small droplets from a large droplet. A Volume Of Fluid (VOF) method was used and for verifying the accuracy of simulation the results compared with two analytical researches. Our results reveal that breakup time and breakup length of the droplets play important roles in handling these systems optimally. Our results also indicate that for nanoscale T-junctions by increasing the capillary number the performance increases while for the micro-scale systems there is a specific capillary number for which the system is in its optimum condition.

Numerical Investigation of Droplets Breakup in a Microfluidic T-Junction

2011 ◽  
Vol 110-116 ◽  
pp. 3269-3277 ◽  
Author(s):  
Ahmad Bedram ◽  
Ali Moosavi
Keyword(s):  
Optimum Condition ◽  
Numerical Investigation ◽  
Capillary Number ◽  
Volume Of Fluid ◽  
Vof Method ◽  
Equal Size ◽  
Width Ratio ◽  
Unequal Size ◽  
Breakup Time ◽  
Good Agreement

A Volume of Fluid (VOF) method is used to study the breakup of droplets in T-junction geometries. Symmetric T-junctions, which are used to produce equal size droplets and have many applications in pharmacy and chemical industries, are considered. Two important factors namely "breakup time" and "breakup length" that can improve the performance of these systems have been introduced. In addition a novel system which consists of an asymmetric T-junction is proposed to produce unequal size droplets. The effects of the channel width ratio and the capillary number on the size and length of the generated droplets and also the time of the generation have been studied and discussed. For simulation the problem, a VOF method used and for verifying the accuracy of the simulation the results compared with two analytical researches and a good agreement was found. The results indicate for the systems that generate equal size droplets, in a specific Capillary number (in our case 0.02) the performance of the system is in its optimum condition. Also for the systems that generate unequal size droplets, in large capillary numbers a wider range of droplets with different sizes can be produced.

Numerical Investigation of an Efficient Method (T-Junction With Valve) for Producing Unequal-Sized Droplets in Micro- and Nano-Fluidic Systems

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Ahmad Bedram ◽  
Amir Ebrahim Darabi ◽  
Ali Moosavi ◽  
Siamak Kazemzade Hannani
Keyword(s):  
Pressure Drop ◽  
Efficient Method ◽  
Capillary Number ◽  
Numerical Scheme ◽  
Volume Ratio ◽  
Droplet Breakup ◽  
Breakup Process ◽  
Breakup Length ◽  
Breakup Time ◽  
Arbitrary Volume

We investigate an efficient method (T-junction with valve) to produce nonuniform droplets in micro- and nano-fluidic systems. The method relies on breakup of droplets in a T-junction with a valve in one of the minor branches. The system can be simply adjusted to generate droplets with an arbitrary volume ratio and does not suffer from the problems involved through applying the available methods for producing unequal droplets. A volume of fluid (VOF) based numerical scheme is used to study the method. Our results reveal that by decreasing the capillary number, smaller droplets can be produced in the branch with valve. Also, we find that the droplet breakup time is independent of the valve ratio and decreases with the increase of the capillary number. Also, the results indicate that the whole breakup length does not depend on the valve ratio. The whole breakup length decreases with the decrease of the capillary number at the microscales, but it is independent of the capillary number at the nanoscales. In the breakup process, if the tunnel forms the pressure drop does not depend on the valve ratio. Otherwise, the pressure drop reduces linearly by increasing the valve ratio.

Advanced understanding of local wetting behaviour in gas-liquid-solid packed beds using CFD with a volume of fluid (VOF) method

2017 ◽  
Vol 170 ◽  
pp. 378-392 ◽  
Author(s):  
Wei Du ◽  
Jianzhou Zhang ◽  
Panpan Lu ◽  
Jian Xu ◽  
Weisheng Wei ◽  
...  
Keyword(s):  
Volume Of Fluid ◽  
Vof Method ◽  
Packed Beds

scholarly journals 3-D numerical modelling of crustal polydiapirs with volume-of-fluid methods

2020 ◽  
Vol 222 (1) ◽  
pp. 474-506
Author(s):  
Aurélie Louis-Napoléon ◽  
Muriel Gerbault ◽  
Thomas Bonometti ◽  
Cédric Thieulot ◽  
Roland Martin ◽  
...  
Keyword(s):  
Volume Of Fluid ◽  
Vof Method ◽  
Earth’S Crust ◽  
Gravitational Instabilities ◽  
Interface Reconstruction ◽  
Rayleigh Taylor Instability ◽  
Earth's Crust ◽  
Two Stages ◽  
Rayleigh Benard ◽  
Earth Dynamics

SUMMARY Gravitational instabilities exert a crucial role on the Earth dynamics and in particular on its differentiation. The Earth’s crust can be considered as a multilayered fluid with different densities and viscosities, which may become unstable in particular with variations in temperature. With the specific aim to quantify crustal scale polydiapiric instabilities, we test here two codes, JADIM and OpenFOAM, which use a volume-of-fluid (VOF) method without interface reconstruction, and compare them with the geodynamics community code ASPECT, which uses a tracking algorithm based on compositional fields. The VOF method is well-known to preserve strongly deforming interfaces. Both JADIM and OpenFOAM are first tested against documented two and three-layer Rayleigh–Taylor instability configurations in 2-D and 3-D. 2-D and 3-D results show diapiric growth rates that fit the analytical theory and are found to be slightly more accurate than those obtained with ASPECT. We subsequently compare the results from VOF simulations with previously published Rayleigh–Bénard analogue and numerical experiments. We show that the VOF method is a robust method adapted to the study of diapirism and convection in the Earth’s crust, although it is not computationally as fast as ASPECT. OpenFOAM is found to run faster than, and conserve mass as well as JADIM. Finally, we provide a preliminary application to the polydiapiric dynamics of the orogenic crust of Naxos Island (Greece) at about 16 Myr, and propose a two-stages scenario of convection and diapirism. The timing and dimensions of the modelled gravitational instabilities not only corroborate previous estimates of timing and dimensions associated to the dynamics of this hot crustal domain, but also bring preliminary insight on its rheological and tectonic contexts.

An Improved Anti-Diffusive VOF Method to Predict Two-Fluid Free Surface Flows

2011 ◽  
Author(s):  
Y. G. Chen ◽  
W. G. Price ◽  
P. Temarel
Keyword(s):  
Free Surface ◽  
Diffusion Processes ◽  
Volume Fraction ◽  
Volume Of Fluid ◽  
Free Surface Flows ◽  
Vof Method ◽  
Advection Equation ◽  
Diffusion Term ◽  
Surface Flows ◽  
Two Fluid

This investigation continues the development of an anti-diffusive volume of fluid method [1] by improving accuracy through the addition of an artificial diffusion term, with a negative diffusion coefficient, to the original advection equation describing the evolution of the fluid volume fraction. The advection and diffusion processes are split into a set of two partial differential equations (PDEs). The improved anti-diffusive Volume of Fluid (VOF) method is coupled with a two-fluid flow solver to predict free surface flows and illustrated by examples given in two-dimensional flows. The first numerical example is a solitary wave travelling in a tank. The second example is a plunging wave generated by flow over a submerged obstacle of prescribed shape on a horizontal floor. The computational results are validated against available experimental data.

scholarly journals A Volume of Fluid (VOF) Method for the Simulation of Metallurgical Flows

2001 ◽  
Vol 41 (3) ◽  
pp. 225-233 ◽  
Author(s):  
Petar Liovic ◽  
Jong-Leng Liow ◽  
Murray Rudman
Keyword(s):  
Volume Of Fluid ◽  
Vof Method
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