Search for: phase-interfaces
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    Calcium chloride adsorption at liquid-liquid interfaces: A molecular dynamics simulation study

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 527 , 2017 , Pages 70-80 ; 09277757 (ISSN) Khiabani, N. P ; Bahramian, A ; Chen, P ; Pourafshary, P ; Goddard, W.A., III ; Ejtehadi, M. R ; Sharif University of Technology
    We carried out molecular dynamics simulations (MD) to investigate the adsorption of calcium chloride (CaCl2) at n-hexane-water interfaces. We also measured the interfacial tensions (IFT) of the selected systems making use of the pendant-drop method. The histograms of hexane, water, and the ions indicate an electrical double layer (EDL) near the interface. The trend of the EDL indicates that chloride anions intend to adsorb to the interface more intrinsically than calcium cations. The measured interfacial width of the n-hexane-water interfaces decreases with the salt concentration. The average densities of the interfacial and bulk aqueous solutions demonstrate density heterogeneity in the... 

    How important is the liquid bulk viscosity effect on the dynamics of a single cavitation bubble?

    , Article Ultrasonics Sonochemistry ; Volume 49 , 2018 , Pages 47-52 ; 13504177 (ISSN) Nazari Mahroo, H ; Pasandideh, K ; Navid, H. A ; Sadighi Bonabi, R ; Sharif University of Technology
    The influence of liquid bulk viscosity on the dynamics of a single cavitation bubble is numerically studied via Gilmore model with a new modified boundary condition at bubble interface. In order to more accurately describe the interior gas thermodynamics, a hydrochemical model is used. The numerical results for an argon bubble in water and aqueous H2SO4 show that including the liquid bulk viscosity slightly affects the bubble dynamics in collapse phase. This effect becomes significant only at high ultrasonic amplitudes and high viscosities. Moreover, the maximum pressure value inside the bubble is much more influenced than the maximum temperature. This finding lends support to results of... 

    Thermal optimization of the continuous casting process using distributed parameter identification approach—controlling the curvature of solid-liquid interface

    , Article International Journal of Advanced Manufacturing Technology ; Volume 94, Issue 1-4 , 2018 , Pages 1101-1118 ; 02683768 (ISSN) Tavakoli, R ; Sharif University of Technology
    Springer London  2018
    Thermal optimization of the vertical continuous casting process is considered in the present study. The goal is to find the optimal distribution of the temperature and interfacial heat transfer coefficients corresponding to the primary and secondary cooling systems, in addition to the pulling speed, such that the solidification along the main axis of strand approaches to the unidirectional solidification mode. Unlike many thermal optimization of phase change problems in which the desirable (target) temperature, temperature gradient, or interface position are assumed to be a priori known, a desirable shape feature of the freezing interface (not its explicit position) is assumed to be known in... 

    The effects of pH, acidity, asphaltene and resin fraction on crude oil/water interfacial tension

    , Article Journal of Petroleum Science and Engineering ; Volume 162 , 2018 , Pages 341-347 ; 09204105 (ISSN) Lashkarbolooki, M ; Ayatollahi, S ; Sharif University of Technology
    Elsevier B.V  2018
    A basic understanding of the activities of indigenous surfactants of crude oil at the water/oil interface as a function of aqueous phase pH can give us a better insight into the alkaline enhanced oil recovery processes. The present study aimed to elucidate the effect of salinity and crude oil type, specifically the influence of resin and asphaltene molecules during alkaline flooding through interfacial tension (IFT) measurements via pendant drop and spinning techniques. Several model oils containing asphaltene and resin fractions were prepared and their IFTs were compared with those of the original crude oils. Moreover, the elemental analyses of asphaltene and resin fractions were performed,... 

    CFD-DEM modeling of cuttings transport in underbalanced drilling considering aerated mud effects and downhole conditions

    , Article Journal of Petroleum Science and Engineering ; Volume 160 , 2018 , Pages 229-246 ; 09204105 (ISSN) Akhshik, S ; Rajabi, M ; Sharif University of Technology
    Elsevier B.V  2018
    This paper presents a developed CFD (Computational fluid dynamics)-DEM (Discrete elements method) model to study the cuttings transportation in aerated mud drilling process for inclined annuli at downhole conditions. The model is conducted to determine the effects of liquid flow rate, air injection rate, annulus inclination angle, elevated temperature and pressure on the cuttings transport efficiency. The motion of the fluid is computed using CFD based approach with gas–liquid interface capturing provided by the volume-of-fluid (VOF) method. The dynamics of cutting phase is studied by DEM using soft sphere approach in order to take into account the particle collision phenomenon. The... 

    Characterization of liquid bridge formed during gas-oil gravity drainage in fractured porous media

    , Article 16th European Conference on the Mathematics of Oil Recovery, ECMOR 2018, 3 September 2018 through 6 September 2018 ; 2018 ; 9789462822603 (ISBN) Harimi, B ; Masihi, M ; Ghazanfari, M. H ; Shoushtari, A ; Sharif University of Technology
    European Association of Geoscientists and Engineers, EAGE  2018
    Gas-oil gravity drainage that takes place in the gas-invaded zone of fractured reservoirs is the main production mechanism of gas-cap drive fractured reservoirs as well as fractured reservoirs subjected to gas injection. Interaction of neighboring matrix blocks through reinfiltration and capillary continuity effects controls the efficiency of gravity drainage. Existence of capillary continuity between adjacent matrix block is likely to increase the ultimate recovery significantly. Liquid bridge formed in fractures has a significant role in maintaining the capillary continuity between two neighboring matrix blocks. The degree of capillary continuity is proportional to capillary pressure in... 

    Advancement in numerical study of gas flow and heat transfer in microscale

    , Article Journal of Thermophysics and Heat Transfer ; Volume 23, Issue 1 , 2009 , Pages 205-208 ; 08878722 (ISSN) Vakilipour, S ; Darbandi, M ; Sharif University of Technology
    The gas flow and heat transfer in a long microscopic channel with inlet-to-outlet pressure ratio equal to 8000 is studied. The second-order slip velocity and temperature jump boundary conditions are used, which are derived using a gas-surface interface mechanisms. The inlet is discretized to 19 nodes and they are clustered near the wall, while the longitudinal dimension in discretized to 1500 divisions using a nonuniform grid distribution. The current velocity profiles are found to have a good agreement with high-order analytical solutions, indicating that the current velocity perform second-order accuracy. The pressure distributions are found to perform higher nonlinearity as the... 

    Effect of rare earth elements addition on thermal fatigue behaviors of AZ91 magnesium alloy

    , Article Journal of Rare Earths ; Volume 27, Issue 2 , 2009 , Pages 255-258 ; 10020721 (ISSN) Bayani, H ; Saebnoori, E ; Sharif University of Technology
    Chinese Society of Rare Earths  2009
    Influences of rare earth (RE) elements addition on thermal fatigue behaviors of AZ91 alloy were studied. Repeated heating and cooling cycles were applied on the samples at 170 and 210 °C to develop thermal fatigue cracks. Crack growth mechanisms and microstructural influences were investigated by optical and scanning electron microscopy (SEM) as well as energy dispersive X-ray spectroscopy (EDS). Thermal fatigue behaviors were observed to improve successively by addition of the RE up to 2wt.%. This improvement was attributed to the consummation of aluminum in melt by precipitation of the needle shaped Al11RE3 phases. This process was attributed to the reduction of Mg17Al12 phase volume... 

    Computational simulation of marangoni convection under microgravity condition

    , Article Scientia Iranica ; Volume 16, Issue 6 B , 2009 , Pages 513-524 ; 10263098 (ISSN) Saidi, M. H ; Taeibi Rahni, M ; Asadi, B ; Ahmadi, G ; Sharif University of Technology
    In this work, the rising of a single bubble in a quiescent liquid under microgravity condition was simulated. In addition to general studies of microgravity effects, the initiation of hydrodynamic convection, solely due to the variations of interface curvature (surface tension force) and thus the generation of shearing forces at the interfaces, was also studied. Then, the variation of surface tension due to the temperature gradient (Marangoni convection), which can initiate the onset of convection even in the absence of buoyancy, was studied. The related unsteady incompressible full Navier-Stokes equations were solved using a finite difference method with a structured staggered grid. The... 

    Improved adhesion of NiTi wire to silicone matrix for smart composite medical applications

    , Article Materials and Design ; Volume 30, Issue 9 , 2009 , Pages 3667-3672 ; 02641275 (ISSN) Sadrnezhaad, Kh ; Hassanzadeh Nemati, N ; Bagheri, R ; Sharif University of Technology
    Recent uses of intelligent composites in biomedical appliances aggrandize the necessity of bonding-strength improvement in NiTi/silicone matrix interface. SEM micrographs and pull-out tests are employed to determine the strength of the NiTi/silicone bonds in a flexible composite piece. Greater adhesion strengths are obtained due to the presence of thin oxide layer, surface roughness and frictional forces between the embedded-wires and the contacting phase. Effect of curing treatment on phase transformation temperatures of the wires is determined by electrical resistivity (ER) measurements. Results show that the curing treatment shifts the transition points of the wires towards higher... 

    Roles of preoxidation, Cu2O particles, and interface pores on the strength of eutectically bonded Cu/α-Al2O3

    , Article Materials and Design ; Volume 30, Issue 4 , 2009 , Pages 1098-1102 ; 02641275 (ISSN) Ghasemi, H ; Kokabi, A. H ; Faghihi Sani, M. A ; Riazi, Z ; Sharif University of Technology
    The influences of CuO layer thickness, Cu2O particles, and pores on mechanical properties and microstructure of alumina-copper eutectic bond have been investigated. The furnace atmosphere in the first stage was argon gas with 2 × 10-6 atm oxygen partial pressure. In the second stage, the furnace atmosphere was same as the first stage except for the cooling interval between 900 and 1000 °C, the hydrogen gas was injected into furnace atmosphere. Finally, in the last stage a vacuum furnace with 5 × 10-8 atm pressure was chosen for bonding procedure. Peel strength of first stage specimens shows that CuO layer with 320 ± 25 nm thick generates the maximum peel strength (13.1 ± 0.3 kg/cm) in joint... 

    Interfacial instability of growing drop: experimental study and conceptual analysis

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 347, Issue 1-3 , 2009 , Pages 167-174 ; 09277757 (ISSN) Javadi, A ; Bastani, D ; Kragel, J ; Miller, R ; Sharif University of Technology
    Elsevier  2009
    Capillary pressure experiments were performed at the water/hexane interface including adsorption and mass exchange of hexanol under different conditions. The results from growing drop experiments show that instabilities due to Marangoni convection not only depend on the same parameters as have been reported for quasi-static interfaces, such as direction of mass transfer, distribution coefficient and ratio of diffusion coefficients, but also on the experimental conditions such as dispersed phase flow rate, capillary tip size, size of growing drop and its lifetime. Based on a new flow expansion model for mass transfer, a new approach is presented for data analysis, which includes the various... 

    A new method in two phase flow modeling of a non-uniform grid

    , Article Scientia Iranica ; Volume 16, Issue 5 B , 2009 , Pages 425-439 ; 10263098 (ISSN) Bohluly, A ; Borghei, M ; Saidi, M. H ; Sharif University of Technology
    In this paper, a two dimensional numerical model for two phase flow is presented. For interface tracking, the FGVT-VOF (Fine Grid Volume Tracking-Volume Of Fluid) method is selected. For momentum advection, an improved approach is used. In this scheme, a volume tracking step is coupled with steps of computations for the advection of momentum. A Reynolds stress algebraic equation has been implemented in the algorithm of turbulent modeling. Standard test cases are used for the verification of interface tracking and hydrodynamic modeling in laminar and turbulent conditions. The test results show that this methodology can be used in different applications of two-phase flow modeling. © Sharif... 

    Effect of magnesium addition on the wetting of alumina by aluminium

    , Article Applied Surface Science ; Volume 255, Issue 19 , 2009 , Pages 8202-8206 ; 01694332 (ISSN) Sangghaleh, A ; Halali, M ; Sharif University of Technology
    In this report the wetting behaviour between polycrystalline alumina substrates and molten aluminium doped with magnesium as a wetting agent has been studied using the sessile drop technique. The time required for equilibrium attainment is investigated. To explore the formation of possible phases at the interface, electron microscopic studies along with EDX analysis have been employed. It is found that magnesium reduces the time and temperature required for equilibrium in the Al/Al2O3 system. The Al-7 wt% Mg and Al-10 wt% Mg alloys can wet alumina at temperatures as low as 900 °C. It is also found that molten aluminium doped with magnesium can wet polycrystalline alumina at temperatures... 

    Laboratory evaluation of nitrogen injection for enhanced oil recovery: Effects of pressure and induced fractures

    , Article Fuel ; Volume 253 , 2019 , Pages 607-614 ; 00162361 (ISSN) Fahandezhsaadi, M ; Amooie, M. A ; Hemmati Sarapardeh, A ; Ayatollahi, S ; Schaffie, M ; Ranjbar, M ; Sharif University of Technology
    Elsevier Ltd  2019
    Nitrogen has emerged as a suitable alternative to carbon dioxide for injection into hydrocarbon reservoirs worldwide to enhance the recovery of subsurface energy. Nitrogen typically costs less than CO2 and natural gas, and has the added benefit of being widely available and non-corrosive. However, the underlying mechanisms of recovery following N2 injection into fractured reservoirs that make up a large portion of the world's oil and gas reserves are not well understood. Here we present the laboratory results of N2 injection into carbonate rocks acquired from a newly developed oil reservoir in Iran with a huge N2-containing natural gas reservoir nearby. We investigate the effectiveness of N2... 

    Influence of PEO and mechanical keying on the strength of AA 5052 alloy/polypropylene friction stir spot welded joints

    , Article International Journal of Adhesion and Adhesives ; Volume 92 , 2019 , Pages 65-72 ; 01437496 (ISSN) Aliasghari, S ; Skeldon, P ; Zhou, X ; Ghorbani, M ; Sharif University of Technology
    Elsevier Ltd  2019
    A study has been carried out of the effect of plasma electrolytic oxidation (PEO)on the strength of AA 5052 alloy/polypropylene joints prepared using friction stir spot welding (FSSW). The joint strengths were determined using lap-shear tests and failure modes were investigated using scanning electron microscopy. Comparisons were made between control joints prepared with the alloy in the as-rolled condition or the as-rolled condition with a mechanical key and with PEO-treated alloy, with or without a mechanical key. Mechanical keying alone, provided by infiltration of polymer into holes of either 3 or 4.5 mm diameter drilled in the alloy, yielded enhancements of the joint strength by a... 

    New approaches in lowering the gas-phase synthesis temperature of TiO2 nanoparticles by H2O-assisted atmospheric pressure CVS process

    , Article Journal of Materials Research and Technology ; Volume 8, Issue 3 , 2019 , Pages 3024-3035 ; 22387854 (ISSN) Rahiminezhad Soltani, M ; Saberyan, K ; Simchi, A ; Gammer, C ; Sharif University of Technology
    Elsevier Editora Ltda  2019
    H2O-assisted atmospheric pressure chemical vapor synthesis is a modern economical process for the gas-phase synthesis of TiO2 nanoparticles. In the present work, the influence of synthesis temperatures (100-800 °C) on the phase structure, nanoparticle size, morphology, and agglomeration is investigated by transmission electron microscopy, selected area electron diffraction, X-ray diffraction, thermogravimetry, and differential thermal analysis. Down to 400 °C, crystalline TiO2 nanoparticles are synthesized and at 200 °C amorphous nanoparticles are formed. Therefore, a decrease in minimum synthesis temperature by more than 500 °C is achieved. In addition, the paper investigates the hypothesis... 

    Optimization of microgrooves for water–solid drag reduction using genetic algorithm

    , Article Journal of Ocean Engineering and Marine Energy ; Volume 6, Issue 3 , 2020 , Pages 221-242 Abdollahzadeh, M. J ; Moosavi, A ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2020
    The friction on the water–solid interfaces continues to be the most important factor for the energy loss in many marine and submarine applications. Therefore, different techniques have been developed and are available to reduce friction and, as a result, the overall cost. In the past decades, the use of structured surfaces has been given considerable attention because of their specific characteristics such as their abilities in pressure drop reduction. However, an appropriate optimization method is required to find the best surface structure. In the present study, we consider a microgrooved substrate and examine the performance of three shapes including rectangular, elliptical, and... 

    Modeling of reactive acid transport in fractured porous media with the Extended–FEM based on Darcy-Brinkman-Forchheimer framework

    , Article Computers and Geotechnics ; Volume 128 , December , 2020 Khoei, A. R ; Salehi Sichani, A ; Hosseini, N ; Sharif University of Technology
    Elsevier Ltd  2020
    In this paper, a fully coupled numerical model is developed based on the X-FEM technique to simulate the reactive acid transport in fractured porous media. The porous medium consists of the solid and fluid phases, in which the fluid phase includes water and acid components, and chemical reactions can be occurred between acid component and solid phase at the solid–fluid interfaces. The governing equations include the mass and momentum conservation laws for fluid phase, and the advective–diffusive transport of acid component that must be solved to obtain the primary unknowns, including the pore fluid pressure, acid concentration, and fluid velocity vector. Applying the... 

    A model based on the equality of chemical potentials for describing the liquid-liquid interfaces of water-hydrocarbons up to high pressures

    , Article Journal of Molecular Liquids ; Volume 317 , November , 2020 Khosharay, S ; Feyzi, P ; Tourang, S ; Tajfar, F ; Sharif University of Technology
    Elsevier B. V  2020
    A reliable model was used to describe the interfacial tension, composition, and density of the liquid-liquid interfaces of water-hydrocarbons. The parachor model was combined with the equality of the chemical potential of components at the interface and the bulk liquid. The fugacity coefficient was used for computing chemical potentials. To compute the fugacity coefficients of the components, various types of equations of state (The Valderrama Patel-Teja, cubic plus association, and the simplified Perturbed-Chain Statistical Association Fluid Theory) were utilized. These models were applied to the temperature and the pressure range of (285.65–423) K and (1–3000) bar, respectively. The...