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    Effects of various parameters on the coating of substrates with trenches

    , Article 2012 International Conference on Advanced Materials Design and Mechanics, ICAMDM 2012, Xiamen, 5 June 2012 through 7 June 2012 ; Volume 569 , 2012 , Pages 219-222 ; 10226680 (ISSN) ; 9783037854808 (ISBN) Mazloomi, A ; Moosavi, A ; Sharif University of Technology
    We investigate thin liquid film coating of substrates with trenches via lattice Boltzmann method. The effects of different parameters such as the capillary number, the contact angles and geometric parameters on the results are studied. Our results indicate that for trench depths greater than a critical size coating of the trench is not successful. The critical depth increases by decreasing the capillary number. Moreover we find height, width, capillary number and contact angle under which the coating is successful. The results have been compared with the available results and very close agreement has been achieved  

    Gravity-driven thin liquid films over topographical substrates

    , Article European Physical Journal E ; Volume 36, Issue 6 , 2013 ; 12928941 (ISSN) Mazloomi, A ; Moosavi, A ; Esmaili, E ; Sharif University of Technology
    We investigate the time-dependent evolution of thin liquid films over inclined substrates using a multi-component lattice Boltzmann algorithm. Substrates with and without grooves are considered and the effects of the inclination angle on the dynamics and the coating of the substrates are studied. Our results indicate that the dynamics is enhanced and the ridge height and its displacement are increased by increasing the inclination angle. However, by increasing the inclination angle the maximum depth that can be successfully coated is reduced. Also, although for any given groove depth the width should be larger than a critical value for successful coating, the critical width decreases for... 

    Theory of the liquid film motor

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 3 , September , 2015 ; 15393755 (ISSN) Feiz, M. S ; Namin, R. M ; Amjadi, A ; Sharif University of Technology
    American Physical Society  2015
    The liquid film motor is a freely suspended liquid film placed between two capacitively coupled plates that rotates when an electric current is passed through it. Here we propose a theory for its rotation mechanism based on thin film electroconvection. The capacitively coupled plates induce free charges on the surfaces of the film, and the electric field on the film exerts a force that induces rotation. Results of the proposed theory and simulation are in good agreement with the experiments in different properties of the liquid film motor  

    Liquid soap film generates electricity: a suspended liquid film rotating in an external electric field as an electric generator

    , Article Microfluidics and Nanofluidics ; Vol. 18, issue. 1 , Apr , 2014 , pp. 141-147 ; ISSN:16134982 Amjadi, A ; Feiz, M. S ; Namin, R. M ; Sharif University of Technology
    We have observed that a rotating liquid soap film generates electricity when placed between two non-contact electrodes with a sufficiently large potential difference. In our experiments, suspended liquid film (water + soap film) is formed on the surface of a circular frame, which is forced to rotate in the x−y horizontal plane by a motor. This system is located at the center of two capacitor-like vertical plates to apply an external electric voltage difference in the x-direction. The produced electric current is collected from the liquid film using two conducting electrodes that are separated in the y-direction. We previously reported that a liquid film in an external electric field rotates... 

    Laminar falling film flow of aqueous Li Br solution on a horizontal elliptical tube

    , Article International Journal of Fluid Mechanics Research ; Volume 40, Issue 4 , 2013 , Pages 324-343 ; 10642277 (ISSN) Abyaneh, M. H. J ; Saidi, M. H ; Sharif University of Technology
    Flow hydrodynamics of laminar falling film of aqueous Li Br solution (Li Br - H2O) on a horizontal elliptical tube has been investigated in this research. The film velocity distribution and film thickness, namely, the flow characteristics are determined by solving analytically simultaneous simplified Navier - Stokes equations and continuity equation in polar and Cartesian coordinates. The analysis is based on steady state laminar flow of falling liquid film of Li Br - H2O on a horizontal elliptical tube in polar model and Cartesian model (CM), for cases in which traction on the film surface is considered negligible. Models are compared with each other in three cases of aspect ratios (Ar),... 

    Late-stage evolution of thin liquid coating films over step topographies

    , Article Advanced Materials Research ; Volume 569 , 2012 , Pages 560-563 ; 10226680 (ISSN) ; 9783037854808 (ISBN) Asgari, M ; Moosavi, A ; Sharif University of Technology
    Mesoscopic hydrodynamic equations are solved to investigate late-stage evolution of thin liquid films over step topographies. Different geometrical parameters including step height and initial position and configuration of resultant masses of dewetting (droplets) are probed to find their effects on the mass evolution of the system. Our results indicate that increasing the step height and locating the droplets close to the step enhance the dynamics and accelerate smaller droplet collapse  

    Modeling and Simulation of Two Phase Flow in Gas Condensate Wells

    , M.Sc. Thesis Sharif University of Technology Sheikh Hosseini, Saeed (Author) ; Taghikhani, Vahid (Supervisor) ; Ghazanfari, Mohammad Hossein (Supervisor)
    A numerical simulation of fluid flow in gas condensate wellbore, which annular flow is dominant, is performed. A three fluid model is used for annular two phase flow. The model is based on conservation equations of mass, momentum and energy for gas phase, dispersed phase (droplets) and the film. The friction between phases and with wellbore wall and also mass transfer between phases, which conservation equations rely on them, are considered. Computer programming of obtained system of equations is performed in Matlab. The Reimann method is used for solving our system of hyperbolic equations and simulation is performed for both steady and unsteady state. Transforming system of nonlinear... 

    Investigation of Rotational Liquid Film and Electric Power Generation under Electric Field

    , M.Sc. Thesis Sharif University of Technology Feiz, Mohammad Sadegh (Author) ; Amjadi, Ahmad (Supervisor)
    Investigation of electrohydrodynamic behavior of fluids under electric fields is a challenging and impressive matter in condensed matter physics. In this thesis, inspired from previous works on liquid film motor, a new phenomenon has been observed and its properties has been investigated.Here by making a new device named “Liquid Film Electric Generator” we produced potential difference on the rotating suspended liquid film under electric field. The power conducted by electrodes has been generated on the surfaces of the film. By this method, under electric field of 1000 V/cm, micro-watt electric power can be achieved on a liquid film of diameter of about 1 cm.We explained this phenomenon on... 

    Advanced heat transfer analysis of a U-shaped pulsating heat pipe considering evaporative liquid film trailing from its liquid slug

    , Article Applied Thermal Engineering ; Volume 138 , 28 June , 2018 , Pages 475-489 ; 13594311 (ISSN) Nemati, R ; Behshad Shafii, M ; Sharif University of Technology
    Elsevier Ltd  2018
    In order to study the heat transfer mechanism and predict the heat transfer capability of a pulsating heat pipe (PHP), a numerical model was used to simulate the oscillating behavior of liquid slug considering liquid film thickness in the evaporator and reduction of liquid film thickness due to evaporation. In this article, thermal performance of an open loop closed end PHP of copper with a diameter of 1 mm and various working fluids including water (DW) and ethanol was investigated. The governing equations of mass, momentum, and energy equations were solved for liquid slug and vapor plugs. The results showed that by considering liquid film thickness behind the liquid slug, for both the... 

    A three dimensional simulation of spray cooling and its evaporating liquid film generated on patterned surfaces

    , Article International Journal of Multiphase Flow ; Volume 155 , 2022 ; 03019322 (ISSN) Zeraatkardevin, A ; Jowkar, S ; Morad, M. R ; Shen, X ; Sharif University of Technology
    Elsevier Ltd  2022
    Liquid impingement cooling in the form of jet or spray is an appropriate method to remove heat from small surfaces progressively utilized in industry. In this study, numerical simulations are conducted to investigate the effect of surface structure on heat transfer characteristics. Five different three-dimensional structured surfaces are investigated using Euler-Lagrangian approach. The effect of surface structures is discussed on the liquid film thickness, the liquid film velocity, and the heat flux with its uniformity for a given spray and temperature characteristics. The results show that the convective heat transfer strongly depends on both liquid film thickness and velocity. While the... 

    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... 

    Numerical Simulation of Flow Field inside the Liquid-Liquid Pressure Swirl Injector

    , M.Sc. Thesis Sharif University of Technology Janmohammadi, Mahsa (Author) ; Farshchi, Mohammad (Supervisor)
    Numerical simulation of flow fields inside and outside of a pressure-swirl injector is considered in the present study. Injector characteristics such as the injected liquid sheet thickness, liquid sheet breakup length, and spray angle can be accurately captured via numerical simulations and used for the design optimization of an injector. The flow fields inside of a pressure-swirl injector leading to the primary atomization process outside the injector have been simulated assuming laminar flow with periodic boundary conditions using a coupled volume of fluid (VOF) and a level set model for the two phase fluid. The ANSYS Fluent commercial program is used for simulations. The computational... 

    Velocity distributions in (r,θ) directions for laminar flow of a film around horizontal circular tube

    , Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) Abyaneh, M. H. J ; Saidi, M. H ; Sharif University of Technology
    Velocity distributions in (r,θ) directions are evaluated by solving simultaneous simplified Navier-Stokes equations (NSE) and continuity equation (CE) in polar coordinate. The analysis is based on steady state laminar flow of thin falling liquid film on a horizontal circular tube, for cases in which traction on the film surface is considered negligible. It is a common geometry for part of engineering problems such as evaporator, condenser, absorber, generator of absorption chillers and other similar units in mechanical and chemical engineering. Knowledge of the velocity profiles is usually needed for: 1- solving governing energy and species equations 2- estimating the average and film... 

    Thin liquid film flow over substrates with two topographical features

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 87, Issue 2 , 2013 ; 15393755 (ISSN) Mazloomi, A ; Moosavi, A ; Sharif University of Technology
    A multicomponent lattice Boltzmann scheme is used to investigate the surface coating of substrates with two topographical features by a gravity-driven thin liquid film. The considered topographies are U- and V-shaped grooves and mounds. For the case of substrates with two grooves, our results indicate that for each of the grooves there is a critical width such that if the groove width is larger than the critical width, the groove can be coated successfully. The critical width of each groove depends on the capillary number, the contact angle, the geometry, and the depth of that groove. The second groove critical width depends on, in addition, the geometry and the depth of the first groove;... 

    Theoretical modeling of reinfiltration process in naturally fractured reservoirs: A comparative study on traveling liquid bridges and continuum film flow approaches

    , Article Society of Petroleum Engineers - SPE/EAGE Reservoir Characterization and Simulation Conference 2009 - Overcoming Modeling Challenges to Optimize Recovery, 19 October 2009 through 21 October 2009, Abu Dhabi ; Volume 1 , 2009 , Pages 247-269 ; 9781615677443 (ISBN) Dejam, M ; Ghazanfari, M. H ; Masihi, M ; Sharif University of Technology
    Most of the Iranian oil reservoirs are naturally fractured. Reinfiltration is a key proceess which controls oil flow from the upper to the lower matrix block. However, theoretical modeling of fracture aperture as well as fracture dip angle effects on flow rate of drained oil during reinfilteration process remains a topic of debate in the literature. Moreover, there is no reported experience in the literature that compared the oil velocity predicted by traveling oil bridges and continuum film flow approaches. In this work reinfiltration process is modeled through two different approaches: discrete traveling liquid elements and continuum film flow along inclined fractures. For a case study... 

    A liquid film motor

    , Article Microfluidics and Nanofluidics ; Volume 6, Issue 5 , 2009 , Pages 711-715 ; 16134982 (ISSN) Amjadi, A ; Shirsavar, R ; Hamedani Radja, N ; Ejtehadi, M. R ; Sharif University of Technology
    It is well known that electro-hydrodynamical effects in freely suspended liquid films can force liquids to flow. Here, we report a purely electrically driven rotation in water and some other liquid suspended films with full control on the velocity and the chirality of the rotating vortices. The device, which is called "film motor", consists of a quasi two-dimensional electrolysis cell in an external in-plane electric field, crossing the mean electrolysis current density. If either the external field or the electrolysis voltage exceeds some threshold (while the other does not vanish), the liquid film begins to rotate. The device works perfectly with both DC and AC fields. © Springer-Verlag... 

    Effect of Amplitude of Electric Field on the Rotation of Liquid Film

    , M.Sc. Thesis Sharif University of Technology Mashhadi, Meysam (Author) ; Amjadi, Ahmad (Supervisor)
    By direct and alternating electric field applied to thin film of liquid suspended in the air we can spin out and control it. Rotation pattern depends on the geometry of the electrodes and the applied magnetic field. This is called a rotating liquid film (Liquid Film Motor). To determine the cause of rotation, different models have been proposed. In this project we have tried to check the accuracy of any of the models. Using particle velocimetry using the photo, we calculate the velocity pattern. Then, using the Navier-Stokes equation calculate the acceleration and viscosity from the velocity. Then, for a special arrangement using a finite diffrent method, electric potential and the electric... 

    Rotational regimes of freely suspended liquid crystal films under electric current in presence of an external electric field

    , Article Microfluidics and Nanofluidics ; Volume 13, Issue 1 , 2012 , Pages 83-89 ; 16134982 (ISSN) Shirsavar, R ; Amjadi, A ; Ejtehadi, M. R ; Mozaffari, M. R ; Feiz, M. S ; Sharif University of Technology
    The electrohydrodynamic (EHD) vortices produced by an electric current in freely suspended liquid crystal (LC) films of N-(4-methoxybenzylidene)-4- butylaniline (MBBA), convert to a pure rotation in the presence of external electric field (E ext) perpendicular to the current direction. Here, the direction and strength of the rotation are precisely under control by our self-made device called "liquid-film motor". In this paper, we present experimental observations of the EHD fluid flow when external electric field varies from zero to a value in which pure rotation on the liquid crystal (LC) film is observed. We also show experimentally that the presence of external electric field causes a... 

    Induced soap-film flow by non-uniform alternating electric field

    , Article Journal of Electrostatics ; Volume 73 , February , 2015 , Pages 112-116 ; 03043886 (ISSN) Shirsavar, R ; Ramos, A ; Amjadi, A ; Taherinia, J ; Mashhadi, M ; Nejati, A ; Sharif University of Technology
    Elsevier  2015
    Fluid flows generated on soap films by non-uniform alternating electric fields are studied. Two parallel metal rods subjected to an AC voltage are placed perpendicular to the soap film, which is anchored in a dielectric frame. The fluid flow is generated by electrohydrodynamic induction. At very low signal frequencies there is induced surface charge, but there is no tangential electric field at the surface, so there is no force and no flow. Fluid flow is observed increasing the frequency, when there are both surface charge and tangential electric field. The flow velocity increases with decreasing thickness of the soap film  

    Optical spatial phase retarder/modulator by a rotating freely suspended LC film

    , Article Optics Communications ; Volume 380 , 2016 , Pages 442-445 ; 00304018 (ISSN) Saghaei, T ; Feiz, M. S ; Amjadi, A ; Sharif University of Technology
    This study presents a new method to develop a thin controllable retarder/modulator with spatial axial symmetry by rotating a freely suspended of 4-Cyano-4-n-pentylbiphenyl (5CB) and N-(4-methoxybenzylidene)-4-butylaniline (MBBA) liquid crystal films using mechanical method or as a liquid film motor