Search for: droplet
0.007 seconds
Total 139 records

    Experimental Investigation of Mass Transfer by Droplet Using Image Processing

    , M.Sc. Thesis Sharif University of Technology Babak, Pirooz Hashemi (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein ($item.subfieldsMap.e)
    Wide and varied aspects of droplet motion due to its increasing application in various fields has attracted much attention. Analysis of mass transfer from the liquid drop into the other fluid, such as complex and intriguing problems in fluid mechanics, which is very important. Many experimental and numerical studies have been carried out in this case that the evelopment of laboratory equipment and software, are rapidly growing.
    In this study, given the importance of this issue, experimental study on mass transfer in fluid systems solution droplet liquid - liquid extraction, have been considered. Different methods have been discussed to date. In the present study, using image processing... 

    Study of the Effect of Presence of Nano- Particles on the Mass Transfer and Hydrodynamics of Drops

    , M.Sc. Thesis Sharif University of Technology Nozari, Ali (Author) ; Bastani, Daruoosh (Supervisor) ; Goodarznia, Iraj (Supervisor)
    Regarding to the effect of nanoparticles on mass transfer and hydrodynamics characteristics, limited number of studiesavailableinthe literature.In this work, mass transfer performanceand hydrodynamic characteristics nanofluidshavebeeninvestigated in the liquid−liquid extraction process. The chemical system of toluene-acetic acid-water was used, and two Extraction columnswith diameter of 10cm and height of 55cm and 6 cm were designed. The drops were organic nanofluids containing silica nano-particles and carbon nano-tubes.Synthesized silica nanoparticles by sol-gel methods, were modified with Triethoxyoctylsilane and Polydimethylsiloxane as well as Carbon nano-tubes were modified with dodecyl... 

    Hydrodynamic Investigation of Large Drops and Their Breakage In Liquid Liquid Packed Beds

    , M.Sc. Thesis Sharif University of Technology Davari, Susan (Author) ; Safekordi, Ali Akbar (Supervisor)
    packed columns are important in liquid-liquid extraction processes. In most studies, at first, drops are broken to small drops as much as possible and then they contact with packings. But, because of different reasons drops during their moving up coalescence together. So far, there is not serious investigation about hydrodynamics of these large drops and their breakage in packed columns. Thus, breakage of two different sizes of drops while collision to 3 different height of 4 different type of packings with two volumetric flow rates and in 2 cases of straight collision of drops to bed and collision to support plate has been investigated. Then size distribution of produced drops throughout... 

    The Passive Design and Development of Digital Microfluidic Dynamic Memor

    , M.Sc. Thesis Sharif University of Technology Aminizadeh, Javad (Author) ; Moosavi, Ali (Supervisor)
    Microfluidics with the ability to control Nano-to-Pico meter volumes have caused the revolution in the systems of analytical biology and chemistry. However, the most Lab-On-Chip technologies (LOCs) depend on external control elements, so a lab is required to operate a chip. Bubble or drop logic through the bubble (drop) can control the flow internally and intrinsically digitally without utilizing of off-chip or moving components. Non-linearity is applied by using mutual drop-drop' effects on reversible linear flow in low Reynolds. for the proper exploitation of microfluidic systems, It is necessary to control droplet generation systems in one chip appropriately. The most crucial part of the... 

    Simulation of a falling droplet in a vertical channel with rectangular obstacles

    , Article European Journal of Mechanics, B/Fluids ; Volume 68 , March-April , 2018 , Pages 108-117 ; 09977546 (ISSN) Merdasi, A ; Ebrahimi, S ; Moosavi, A ; Shafii, M. B ; Kowsary, F ; Sharif University of Technology
    Elsevier Ltd  2018
    Droplet microfluidic systems have attracted a large amount of research due to their numerous applications in biomedical micro-devices and drug discovery/delivery platforms. One of the most important problems in such systems is to investigate deformation, coalescence, and breakup of droplets within the channel. The present study demonstrates numerical simulation of a falling droplet subject to gravitational force in a channel with embedded rectangular obstacles. The lattice Boltzmann method incorporated using He–Chen–Zhang method for two phase flow is employed. Two rectangular obstacles with inverse aspect ratios are introduced to investigate the mechanism of breakup and deformation of the... 

    Ferrofluid droplet manipulation using an adjustable alternating magnetic field

    , Article Sensors and Actuators, A: Physical ; Volume 301 , 2020 Bijarchi, M. A ; Favakeh, A ; Sedighi, E ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2020
    Magnetically actuated droplet manipulation offers a promising tool for biomedical and engineering applications, such as drug delivery, biochemistry, sample handling in lab-on-chip devices and tissue engineering. In this study, characteristics of an adjustable alternating magnetic field generated by a magnetic coil for droplet manipulation was investigated which enables more control on droplet transport, and it can be considered as a suitable alternative for moving magnets or an array of micro-coils. By adjusting the magnetic flux density, the duty cycle and applied magnetic frequency, the manipulation of water-based ferrofluid droplets with a bio-compatible surfactant for different volumes... 

    An interface–particle interaction approach for evaluation of the co-encapsulation efficiency of cells in a flow-focusing droplet generator

    , Article Sensors (Switzerland) ; Volume 20, Issue 13 , 2020 , Pages 1-17 Yaghoobi, M ; Saidi, M. S ; Ghadami, S ; Kashaninejad, N ; Sharif University of Technology
    MDPI AG  2020
    Droplet-based microfluidics offers significant advantages, such as high throughput and scalability, making platforms based on this technology ideal candidates for point-of-care (POC) testing and clinical diagnosis. However, the efficiency of co-encapsulation in droplets is suboptimal, limiting the applicability of such platforms for the biosensing applications. The homogeneity of the bioanalytes in the droplets is an unsolved problem. While there is extensive literature on the experimental setups and active methods used to increase the efficiency of such platforms, passive techniques have received less attention, and their fundamentals have not been fully explored. Here, we develop a novel... 

    Flow regime mapping for a two-phase system of aqueous alginate and water droplets in T-junction geometry

    , Article Physics of Fluids ; Volume 33, Issue 7 , 2021 ; 10706631 (ISSN) Mehraji, S ; Saadatmand, M ; Sharif University of Technology
    American Institute of Physics Inc  2021
    Microfluidic systems are an interesting topic for investigation due to their wide-spreading applications. Nowadays, polymeric solutions are used mainly for the generation of microparticles in biomedical engineering, food, and pharmaceutical industries. Droplet-based microfluidic devices have proposed an extensive interest in many applications such as chemical/biological/nanomaterial preparation to understand deeply the droplet size and formation in microchannels. However, numerous experimental and numerical studies have been done for oil-water combination, polymeric solutions behavior in the presence of oil has not been investigated widely. Therefore, it is important to understand the... 

    Numerical simulation of vortex engine flow field: One phase and two phases

    , Article Journal of Thermal Science ; Volume 18, Issue 3 , 2009 , Pages 226-234 ; 10032169 (ISSN) Najafi, A. F ; Saemi, S. D ; Saidi, M. H ; Sharif University of Technology
    Aiming at improving efficiency in combustion systems, the study on droplet behavior and its trajectory is of crucial importance. Vortex engine is a kind of internal combustion engine which uses swirl flow to achieve higher combustion efficiency. One of the important advantages of designing vortex engine is to reduce the temperature of walls by confining the combustion products in the inner vortex. The scopes of this investigation are to study vortex engine flow field as well as effective parameters on fuel droplet behavior such as droplet diameter, droplet initial velocity and inlet velocity of the flow field. The flow field is simulated using Reynolds Stress Transport Model (RSM). The... 

    Experimental investigation of rheological and morphological properties of water in crude oil emulsions stabilized by a lipophilic surfactant

    , Article Journal of Dispersion Science and Technology ; Volume 34, Issue 3 , Feb , 2013 , Pages 356-368 ; 01932691 (ISSN) Sadeghi, M. B ; Ramazani, S. A. A ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
    Rheological behavior of two crude oils and their surfactant-stabilized emulsions with initial droplet sizes ranging from 0.5 to 75 μm were investigated at various temperatures under steady and dynamic shear testing conditions. In order to evaluate the morphology and Stability of emulsions, microscopic analysis was carried out over three months and average diameter and size distribution of dispersed droplets were determined. The water content and surfactant concentration ranged from 10 to 60% vol/vol and 0.1 to 10% wt/vol, respectively. The results indicated that the rheological properties and the physical structure and stability of emulsions were significantly influenced by the water content... 

    Simulation of Droplet Formation and Detachment, Using Lattice Boltzmann Method

    , M.Sc. Thesis Sharif University of Technology Haghshenas, Majid (Author) ; Taeibi Rahni, Mohammad (Supervisor)
    The phenomena of formation and detachment of droplets are of fundamental importance in studying two-phase flows, such as spraying processes, ink jet printing, emulosin, etc. Droplets are formed under the effects of surface tension forces. After formation, forces like gravity detach the droplet from the rest of the fluid. Recent advancements in computational fluid dynamics and computers have made it feasible to have advancement in simulation of complex flows, including two-phase phenomenon. On the other hand, the lattice Boltzmann method (LBM) has been developed into an alternative and promising numerical scheme for simulating multi-component fluid flows.
    In this project, formation and... 

    Analytical and Numerical Study of Dynamics of Wettability Driven Droplets in Smooth And Corrugated Channels

    , M.Sc. Thesis Sharif University of Technology Esmaili, Ehsan (Author) ; Moosavi, Ali (Supervisor)
    We studied dynamics of droplets inside channels under surface forces created by chemicalsteps on the channel walls. A multi-component Shan-Chen lattice Boltzmann method isused for this purpose.The effects of parameters such as the channel height, viscosity anddensity ratios on the results were investigated for homogeneous and grooved substrates. Alsoan analytical solution was developed for droplets under chemical heterogeneities in channels with smooth surfaces. The solution considers a general condition, namely, asymmetry of the contact angles on the top and bottom walls, the viscosity of the gas as the second fluid and the effect of the channel height. Then using Shan-Chen lattice... 

    Topological Defects in Confined Nematics by Planar Anchoring

    , M.Sc. Thesis Sharif University of Technology Seyed Nejad, Reza (Author) ; Ejtehadi, Mohammad Reza (Supervisor) ; Mozaffari, Mohammad Reza (Supervisor)
    Confining nematic liquid crystal between two curved boundary conditions while the nematic molecules have a degenerate planar anchoring leads to complex and beautiful textures of molecular disparagement(defect) in the bulk and on the surfaces. Such the liquid crystal shells are made with double-emulsion techniques in microfluidic devices have provided applications for micro-scale colloidal linkers.In this work, we have numerically minimized the elastic energy in one-constant approximation in present of Fournier’s degenerate surface potential with finite element method. The nematic shell is confined between two spherical surfaces that we have studied the final energies and their related... 

    Numerical Simulation of Forced Impregnation in a Thick Capillary Tube

    , M.Sc. Thesis Sharif University of Technology Safavi, Mohammad (Author) ; Mousavi, Ali (Supervisor)
    Drop penetration into the capillary tube, as a classical problem, has been studied over 100 years. But there are a few studies that investigate forced impregnation of capillary tubes, which has major application in coating, inkjet printing and rain drop penetration into the soil, have been made. A comprehensive numerical investigation on millimeter droplet impact dynamics on a thick capillary tube with micrometer sized pore is conducted and validated against experimental data. This work is extended to oblique impact of drops into pores and normal impact on nanoscaled pores. We apply the finite volume numerical method to solve the time-dependent governing equations of continuity, momentum in... 

    Experimental Analysis of Surface Temperature and Geometry Effects for Drop Impact on Solid Surfaces

    , Ph.D. Dissertation Sharif University of Technology Jowkar, Saeed (Author) ; Morad, Mohammad Reza (Supervisor)
    When a liquid drop impacts on a hot non-flat surface the curvature of the surface and its geometrical characteristics transmute the physical regimes and their boundary compared to a flat surface impact. The present experimental study is focused on water drop impingement on the mimetic solid semi-cylindrical convex and concave hot surfaces. The thermal versus inertia map of generated regimes is obtained, while some well-known regimes associated with a flat surface are not observed for the present non-flat impacts. The maximum spreading of the droplet is measured at different surface temperatures and impact Weber numbers for the case of droplet impingement on the convex surface. In directrix... 

    Numerical Modeling of Drop Formation and Deformation using the Finite Volume Method

    , M.Sc. Thesis Sharif University of Technology Sadat Salehi, Moloud (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Co-Advisor)
    Drop formation from the tip of a nozzle and its motion in bulk fluid is an interesting and practical process which has widely turned researchers’ attention. Investigation into the governing physics and effective parameters on formation, deformation and motion of a drop increases the efficiency of the related industrial processes. Thus in the present study, in order to simulate this process, full Navier-Stokes equations solved by the Volume of Fluid (VOF) method in an axisymmetric domain using Fluent software as the solver. In this research, the effects of Weber number (the proportion of inertial force to surface tension force) and Ohnesorge number (which refers to the proportion of viscous... 

    Numerical and Analytical Investigation of Unequal Size Droplets Generation Process in Micro and Nano Channels

    , Ph.D. Dissertation Sharif University of Technology Bedram, Ahmad (Author) ; Moosavi, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Co-Advisor)
    In this paper, we introduced two methods for producing unequal sized droplet from an initial one that don’t have the disadvantages of the available methods. We developed a comprehensive analytical theory for the T-junction with valve method. Also the geometry was simulated using a VOF algorithm and a comparison was performed between numerical and analytical results and very good agreement was observed. The accuracy of numerical results was confirmed by doing the grid independency and time step independency and comparing the results with two analytical benchmarks. We derived accurate analytical relations for calculating the droplet volume ratio, droplet length (L1, L2 and Lwhole) and pressure... 

    Develoment of Droplet Velocimetry Method Using Shadowgrapy

    , M.Sc. Thesis Sharif University of Technology Abbasi Zarrin, Fatemeh (Author) ; Kebriaee, Azadeh (Supervisor)
    Injection of liquid fuel in the cross-flowing air provides a means of higher penetration, rapid mixing of liquid fuel and air, and is encountered in many engineering applications. Air-breathing propulsion systems (e.g. gas turbine combustors, ramjets, and scramjets), liquid rocket engines,cooling sprays for turbine blades, and injection of fuel in the afterburners are examples of such applications. The identification of microscopic characteristics is one of the basic methods of atomizer examination, which has not been taken into account due to inadequate experimental equipment. In the present study, droplet mono-frame velocimetry and size distribution of secondary atomization in a pressure... 

    Experimental Investigation of Surfactant Effects on Drop Formation of Shear-thinning Liquids

    , M.Sc. Thesis Sharif University of Technology Dastyar, Peyman (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor)
    In this research, the characteristics of non-Newtonian, shear-thinning drop formation containing surfactant from a needle are investigated experimentally. The ambient fluid is air and all experiments have been conducted in a constant flow rate of drop phase fluid. Images of forming drop are taken using a high-speed camera and by processing them, important parameters in drop formation such as length of drop, minimum neck thickness, formation time and the size of satellite drops have been studied. Three non-Newtonian and three Newtonian fluids are considered in a way that the initial viscosity of non-Newtonian fluids would be equal to the viscosity of their corresponding Newtonian fluids.... 

    Numerical Study of Spray Impingement to Solid Wall

    , M.Sc. Thesis Sharif University of Technology Abbasi Chenari, Fatemeh (Author) ; Morad, Mohammad Reza (Supervisor) ; Jahannama, Mohammad Reza (Co-Supervisor)
    Spray-wall impingement is one of the phenomenon that associated in different subject such as spray cooling, combustion chamber and gas turbine. With the impingement of spray to the wall, liquid film begins to form. Wall film characteristics is still an important subject to study. Due to the various stages of liquid film formation from injection of spray till spray-wall impingement, the investigation of this phenomenon is far more complicated. This paper is meant to provide detailed data on spray-wall impingement and wall film formation physics with the help of computational analysis of OpenFOAM . A Lagrangian-Eulerian method based on discrete phase model (DPM) was employed to model...