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Numerical Investigation of Instabilities of Flow in Micro-fluid
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
This research concerns investigating the behavior of two-phase flow in the inlet and outlet of the microchannels.Both the droplet based and the continuous microfluidics are considered. For the continuous system whenthe minor fluid enters the microchannel, due to ratio of viscosity of two fluids, viscous folding occurs.Viscous folding phenomena is similar to the buckling phenomena in solids.This means that the viscosity of the fluid, which is applied to two sides of the fluid layer, causes folding the fluid layer and changing the shape of it. For the study we employ a VOF based numerical routine. In order to verify numerical results, the grid and the time step independenciesare checked. In...
Simulation of Mass Transfer from Droplet in a Two Phase Liquid-liquid Extraction System
, M.Sc. Thesis Sharif University of Technology ; Afshin, Hossein (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
Abstract
Mass transfer of a drop moving in a bulk fluid is an interesting subject which has attracted a lot of attention. Understanding effective parameters in this process would be helpful in order to increase the efficiency of the industrial processes related to mass transfer. In this research, the deformation and mas transfer of a moving drop was studied numerically. Navier-Stokes equations and concentration equation were solved separately with a VOF method in an axisymmetric domain using Fluent software. Comparision between numerical results and former experimental results proves the accuracy of the modelling in both fields of deformation and mass transfer. Moreover, effects of the physical...
Rebounding suppression of droplet impact on hot surfaces: Effect of surface temperature and concaveness
, Article Soft Matter ; Volume 15, Issue 5 , 2019 , Pages 1017-1026 ; 1744683X (ISSN) ; Morad, M. R ; Sharif University of Technology
Royal Society of Chemistry
2019
Abstract
When a droplet impinges on a hot surface it is crucial to increase the contact time or decrease the rebounding distance if the heat transfer between the droplet and the surface is important. This will be more sensitive when the temperature regime is above the Leidenfrost values. The focus of the present experimental study is on the maximum height of drop bouncing after impinging on flat and semi-cylindrical concave surfaces, in particular in terms of surface temperature. It is shown that the behavior of the lamella during the spreading to its maximum diameter has a considerable impact on the maximum height of the drop bouncing. For different impact Weber numbers the map of thermal versus...
Rebounding suppression of droplet impact on hot surfaces: Effect of surface temperature and concaveness
, Article Soft Matter ; Volume 15, Issue 5 , 2019 , Pages 1017-1026 ; 1744683X (ISSN) ; Morad, M. R ; Sharif University of Technology
Royal Society of Chemistry
2019
Abstract
When a droplet impinges on a hot surface it is crucial to increase the contact time or decrease the rebounding distance if the heat transfer between the droplet and the surface is important. This will be more sensitive when the temperature regime is above the Leidenfrost values. The focus of the present experimental study is on the maximum height of drop bouncing after impinging on flat and semi-cylindrical concave surfaces, in particular in terms of surface temperature. It is shown that the behavior of the lamella during the spreading to its maximum diameter has a considerable impact on the maximum height of the drop bouncing. For different impact Weber numbers the map of thermal versus...
Numerical investigation of dynamics of drop motion using lattice boltzmann method
, Article Journal of Molecular Liquids ; Volume 296 , 2019 ; 01677322 (ISSN) ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Dynamics of a drop under the influence of gravitational force was examined using lattice Boltzmann method and color-gradient model. The term associated with the buoyancy force caused by the density difference between the two phases was modified in the lattice Boltzmann equations and verified in some cases. The motion of n-butyl acetate drops in water was predicted in various deformation regimes. The modeling results were in good agreement with the experimental results, solutions obtained by common CFD methods and semi-empirical correlations. Contrary to the common multiphase models, the behavior of moving drops in oscillating regime was predicted with good accuracy using the present model....
Computational Simulation of High Density Ratio Drop Deformation and Breakup, Using Lattice Boltzmann Method
, M.Sc. Thesis Sharif University of Technology ; Taeibi Rahni, Mohammad (Supervisor) ; Karbaschi, Mohsen (Supervisor)
Abstract
Deformation and breakup of drops are the basisof many interfacial flow studies and appear in a number of industrial applications, e.g., spray painting, spray combustion, emulsion, foam, sedimentation, and rain. Following their formation, drops may enter a region where hydrodynamicforces are large enough to cause their significant deformation and breakup. When a drop breaks apart into a multitude of small fragments due to disruptive hydrodynamicforces, the process is termed secondary atomization or breakup. Due to many engineering and scientific applications of multiphase and multi-component flows, they have been the main topic of many researchers for many years. Particularly, interfacial...
Experimental Investigation on the Accelerated Motion of Newtonian and Non-Newtonian Liquid Drops
, M.Sc. Thesis Sharif University of Technology ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
Abstract
Motion of liquid drops into another fluid is of central importance in a variety of most commonly used industries. Vast applications of emulsions in food and drug industries as well as using of drops in liquid-liquid extraction processes and direct contact heat exchangers are examples in which dynamics of motion of drops play a significant role in operation and efficiency.
In present study, we consider the accelerated motion of Newtonian and non-Newtonian liquid drops experimentally. In order to find the effect of bulk fluid on the motion of drops, air and water are used as bulk fluid. The experiments have been done on Water, Ethanol, Ethyl acetate, n-Hexane and Toluene as Newtonian and...
In present study, we consider the accelerated motion of Newtonian and non-Newtonian liquid drops experimentally. In order to find the effect of bulk fluid on the motion of drops, air and water are used as bulk fluid. The experiments have been done on Water, Ethanol, Ethyl acetate, n-Hexane and Toluene as Newtonian and...