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Breakup of droplets in micro and nanofluidic T-junctions
, Article Journal of Applied Fluid Mechanics ; Volume 6, Issue 1 , 2013 , Pages 81-86 ; 17353572 (ISSN) ; Moosavi, A ; Sharif University of Technology
2013
Abstract
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. For this purpose a Volume f Fluid (VOF) based method is used and for verifying the reliability of the numerical outcomes, the results are compared with the available experimental and analytical results. 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 Tjunctions by increasing the capillary number the performance increases while for the micro-scale systems there is a specific capillary number for...
Experimental and Theoretical Investigation of Microdroplet Breakup at Asymmetric T Junctions
, M.Sc. Thesis Sharif University of Technology ; Behshad Shafii, Mohammad (Supervisor)
Abstract
Symmetric T junctions have been used widely in microfluidics to generate equal-sized microdroplets, which are applicable in drug delivery systems. A newly proposed method for generating unequal-size microdroplets at a T junction is investigated theoretically and experimentally. Asymmetric T junctions with branches of identical lengths and different cross-sections are utilized for this aim. A novel equation for the critical breakup of droplets at asymmetric T junctions and one for determining the breakup point of droplets are developed. A good agreement was observed between the theories (novel and previous) and the experiments
Droplet breakup in an asymmetric microfluidic T junction
, Article European Physical Journal E ; Volume 34, Issue 8 , 2011 ; 12928941 (ISSN) ; Moosavi, A ; Sharif University of Technology
2011
Abstract
Breakup of non-uniform droplets in an asymmetric T junction consisting of an inlet channel and two different-size outlet channels has been investigated numerically. Also, an analytical approach in the limit of the lubrication approximation has been extended to provide some analytical relations to study the system and verify the numerical results. Parameters that are important in the performance of the system have been determined and discussed. Our results indicate that smaller droplets can be produced by increasing the capillary number. As the geometry becomes symmetric the pressure drop decreases. Our results also reveal that the breakup time and the pressure drop for this system are...
Analytical relations for long-droplet breakup in asymmetric T junctions
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 91, Issue 5 , May , 2015 ; 15393755 (ISSN) ; Moosavi, A ; Hannani, S. K ; Sharif University of Technology
American Physical Society
2015
Abstract
We develop accurate analytical relations for the droplet volume ratio, droplet length during breakup process, and pressure drop of asymmetric T junctions with a valve in each of the branches for producing unequal-sized droplets. An important advantage of this system is that after manufacturing the system, the size of the generated droplets can be changed simply by adjusting the valves. The results indicate that if the valve ratio is smaller than 0.65, the system enters a nonbreakup regime. Also the pressure drop does not depend on the time and decreases by increasing the valve ratio, namely, opening the degree of valve 1 to valve 2. In addition, the results reveal that by decreasing...
Analytical and numerical study on droplet breakup in microfluidic T-junction
, Article Chemical Engineering and Processing - Process Intensification ; Volume 177 , 2022 ; 02552701 (ISSN) ; Moosavi, A ; Hannani, S. K ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Droplet breakup in symmetric T-junctions is one of the important phenomena in droplet microfluidics. Many studies have been done about the droplet breakup but none of them has provided a general analytical solution for the droplet breakup. In this study, we present an analytical solution to investigate the effect of important parameters such as the capillary number, droplet length, and channel widths ratio. The analytical solution is validated using the numerical simulation. Using the analytical equation and numerical results, we propose a generalized relationship. This general equation can be used as a rule of thumb for droplet breakup predictions with high accuracy. The results indicate...
Ferrofluid droplet breakup process and neck evolution under steady and pulse-width modulated magnetic fields
, Article Journal of Molecular Liquids ; Volume 343 , 2021 ; 01677322 (ISSN) ; Favakeh, A ; Mohammadi, K ; Akbari, A ; Shafii, M. B ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Numerous applications in engineering and biotechnology have attracted the attention of many researchers to the analysis of underlying physical phenomena during the droplet pinch-off. In this study, the neck evolution during the formation of a ferrofluid droplet from a capillary is investigated under two types of magnetic field for a drop-on-demand system. The two types are steady and Pulse-Width Modulated (PWM) magnetic fields. First, under steady magnetic field, the necking process is studied for different values of magnetic Bond number and various angles between magnetic coil centerline and gravity. Subsequently, self-similar behavior in the vicinity of the detachment moment is observed....
Experimental and Numerical Investigation on the Splitting of Microdroplets in Symmetrical and Asymmetrical T Junctions Using Magnetic Fields
, Ph.D. Dissertation Sharif University of Technology ; Shafii, Mohammad Behashad (Supervisor) ; Kazemzadeh Hannani, Siamak (Co-Supervisor)
Abstract
Ferrofluids are used in various fields such as drug delivery systems, heat transfer, biotechnology and separation processes. In this study, the splitting of ferrofluid microdroplets in symmetric and asymmetric T-junctions in the presence of a magnetic field has been investigated numerically and experimentally. These studies have shown that the creation of an asymmetric magnetic field can either affect the phenomenon of ferrofluid microdroplet breakup or the volume of microdroplets that are created after breaking and leaving each branch. Furthermore, more control can be applied to the phenomenon of microdroplet breakup. In the numerical study, the ferrofluid microdroplet breakup at different...
Magnetic field-induced control of a compound ferrofluid droplet deformation and breakup in shear flow using a hybrid lattice Boltzmann-finite difference method
, Article International Journal of Multiphase Flow ; Volume 146 , 2022 ; 03019322 (ISSN) ; Bijarchi, M. A ; Ghorbanpour Arani, A ; Rahimian, M. H ; Shafii, M. B ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The deformation and breakup dynamics of a compound ferrofluid droplet under shear flow and uniform magnetic field are numerically studied in this paper. Utilizing magnetic field provides the possibility to obtain better control over the compound droplet morphology and breakup in a simple shear flow. To solve the governing equations for interfaces motion and hydrodynamics, the conservative phase field lattice Boltzmann model is employed, and a finite difference approach is applied for calculating the magnetic field. To verify the accuracy of present simulations, the results are validated with those of four relevant benchmarks including liquid lens between two stratified fluids, three-phase...