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phase-interfaces
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A comprehensive review on recent advances in superhydrophobic surfaces and their applications for drag reduction
, Article Progress in Organic Coatings ; Volume 140 , March , 2020 ; Pakzad, H ; Moosavi, A ; Nouri Borujerdi, A ; Sharif University of Technology
Elsevier B. V
2020
Abstract
Nowadays, superhydrophobic surfaces have attracted a lot of interest because of the wide range of applications in industries. These surfaces can significantly reduce the drag force due to the formation of air gaps between the substrate and liquid interface. The present review mainly focuses on the very recent progresses in the drag reduction studies using superhydrophobic surfaces. Also, a brief discussion about the mathematical modeling and the theories of superhydrophobic surfaces, natural water repellent surfaces, various fabrication techniques with advantages and disadvantages of each method and different properties of the fabricated surfaces in industrial applications is presented....
Adsorption dynamics of surface-modified silica nanoparticles at solid-liquid interfaces
, Article Langmuir ; Volume 38, Issue 41 , 2022 , Pages 12421-12431 ; 07437463 (ISSN) ; Bastani, D ; Mohammadi, A ; Kordzadeh, A ; Sharif University of Technology
American Chemical Society
2022
Abstract
Understanding the adsorption dynamics of nanoparticles at solid-liquid interfaces is of paramount importance to engineer nanoparticles for a variety of applications. The nanoparticle surface chemistry is significant for controlling the adsorption dynamics. This study aimed to experimentally examine the adsorption of surface-modified round-shaped silica nanoparticles (with an average diameter of 12 nm), grafted with hydrophobic (propyl chains) and/or hydrophilic (polyethylene glycol chains) agents, at an aqueous solution-silica interface with spherical soda-lime glass beads (diameter of 3 mm) being used as adsorbents. While no measurable adsorption was observed for solely hydrophobic or...
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) ; Darbandi, M ; Sharif University of Technology
2009
Abstract
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...
Alumina - copper eutectic bond strength: Contribution of preoxidation, cuprous oxides particles, and pores
, Article 16th International Federation for Heat Treatment and Surface Engineering Congress, Brisbane, QLD, 30 October 2007 through 2 November 2007 ; Volume 32 , 2007 , Pages 90-97 ; 08832900 (ISSN) ; Kokabi, A. H ; Faghihi Sani, M. A ; Riazi, Z ; Sharif University of Technology
2009
Abstract
The influences of cupric oxide layer thickness, cuprous oxide 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 unless that in cooling between 900-1000 °C, the hydrogen gas was purged in 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 cupric oxide layer with 320 ± 25 nm thick generates the maximum peel strength (13.1 ± 0.3...
Alumina-copper eutectic bond strength: contribution of preoxidation, cuprous oxides particles and pores
, Article Scientia Iranica ; Volume 16, Issue 3 B , 2009 , Pages 263-268 ; 10263098 (ISSN) ; Faghihi Sani, M. A ; Kokabi, A. H ; Riazi, Z ; Sharif University of Technology
2009
Abstract
The influences of cupric oxide layer thickness, cuprous oxide particles and pores on the mechanical properties and micro structure of an 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 the. same as the first stage except that the cooling interval was between 900-100l°C and the hydrogen gas was injected into the. furnace, atmosphere. Finally, in the last stage, a vacuum furnace with 5 × 10-8 atra pressure was chosen for the bonding procedure. The peel strength of first stage specimens shows that a, cupric oxide layer with 320 ± 25 ran...
Amino-silane-grafted NH2-MIL-53(Al)/polyethersulfone mixed matrix membranes for CO2/CH4 separation
, Article Dalton Transactions ; Volume 48, Issue 36 , 2019 , Pages 13555-13566 ; 14779226 (ISSN) ; Ahmadipouya, S ; Molavi, H ; Arjmand, M ; Sharif University of Technology
Royal Society of Chemistry
2019
Abstract
Mixed-matrix membranes (MMMs) are promising candidates for carbon dioxide separation. However, their application is limited due to improper dispersion of fillers within the polymer matrix, poor interaction of fillers with polymer chains, and formation of defects and micro-voids at the interface of both phases, which all result in the decline of the gas separation performance of MMMs. In this work, we present a new method to overcome these challenges. To this end, a series of MMMs based on polyethersulfone (PES) as the continuous polymer matrix and MIL-53-derived MOFs as the dispersed filler were prepared. FTIR-ATR, XRD, TGA, FESEM, and N2 adsorption/desorption analyses were employed to...
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 ; Feyzi, P ; Tourang, S ; Tajfar, F ; Sharif University of Technology
Elsevier B. V
2020
Abstract
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...
Analysis of structure-properties relationship in nitrile-butadiene rubber/phenolic resin/organoclay ternary nanocomposites using simple model system
, Article Polymers for Advanced Technologies ; Volume 21, Issue 5 , April , 2010 , Pages 356-364 ; 10427147 (ISSN) ; Faghihi, M ; Sharif University of Technology
2010
Abstract
The present study deals with the structure-property relationship of organoclay (OC) filled nanocomposites based on rubber blend comprising of nitrile-butadiene rubber (NBR) and phenolic resin (PH). To obtain a better insight into the characteristics of the NBR/PH/OC hybrid system, a simple model system consisting of NBR/OC nanocomposites is also taken into consideration. A series of NBR/OC and NBR/PH/OC nanocomposites containing a wide range of OC concentrations (2.5-30 phr) are prepared by using traditional open two-roll mill. Structural analysis performed by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) exhibits mixed exfoliated and...
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) ; Borghei, M ; Saidi, M. H ; Sharif University of Technology
2009
Abstract
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...
A note on the synergistic effect of surfactants and nanoparticles on rising bubble hydrodynamics
, Article Chemical Engineering and Processing - Process Intensification ; Volume 155 , 2020 ; Bastani, D ; Lotfi, M ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Various mixtures of surfactants and nanosilica particles were investigated to assess their influence on rising bubble hydrodynamics. For this purpose, local velocities of rising bubbles were measured experimentally. Also, the effects of concentration of three types of surface-modified silica nanoparticles on density, viscosity, and surface tension of surfactant solutions were determined. Experimental results revealed that the simultaneous presence of nanoparticles and surfactant molecules led to the decrease of local velocities of rising bubbles. The presence of nanoparticles in surfactant solutions leads to a more reduction of bubble local velocity. This could be caused by the formation of...
A review of concentric annular heat pipes
, Article Heat Transfer Engineering ; Volume 26, Issue 6 , 2005 , Pages 45-58 ; 01457632 (ISSN) ; Layeghi, M ; Sharif University of Technology
2005
Abstract
A detailed description of a concentric annular heat pipe (CAHP) operation is presented in low to moderate temperature ranges (50-200°C). The steady-state response of a CAHP to various heat fluxes in the evaporator and condenser sections are discussed. Two-dimensional mathematical modeling of the fluid flow and heat transfer in the annular vapor space and the wicks are described. The fundamental aspects and limitations of the operation of a CAHP are also discussed. Previously used numerical and experimental approaches for the analysis of the CAHPs and some related concepts are reviewed. The Navier-Stokes and similar equations are recommended for the simulation of fluid flow and heat transfer...
Atomistic simulation of creep deformation mechanisms in nickel-based single crystal superalloys
, Article Materials Science and Engineering A ; Volume 809 , 2021 ; 09215093 (ISSN) ; Tolooei Eshlaghi, G ; Shahoveisi, S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
In this paper, the creep deformation mechanisms are investigated in nickel-based single crystal superalloys. Two-dimensional molecular dynamics (MD) simulations are conducted to model various temperatures, stress conditions, and phase interface crystal orientations. Ni-based single-crystal superalloys are of great importance in the aircraft industry due to their excellent high temperature creep resistance. This characteristic mainly originates from two features considered in their structure; firstly, their two-phase micro-structure comprising gamma γ and gamma prime γ′, and secondly the nature of this superalloy itself, which is a single-crystal. MD is a powerful tool to gain insight into...
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) ; Bahramian, A ; Chen, P ; Pourafshary, P ; Goddard, W.A., III ; Ejtehadi, M. R ; Sharif University of Technology
Abstract
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...
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) ; Rajabi, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
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) ; Masihi, M ; Ghazanfari, M. H ; Shoushtari, A ; Sharif University of Technology
European Association of Geoscientists and Engineers, EAGE
2018
Abstract
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...
Comparison and validation of plug and boundary layer flow models of monolithic reactors: Catalytic partial oxidation of methane on Rh coated monoliths
, Article International Journal of Chemical Reactor Engineering ; Volume 6 , 2008 ; 15426580 (ISSN) ; Safekordi, A ; Farhadpour, F. A ; Sharif University of Technology
Walter de Gruyter GmbH
2008
Abstract
Catalytic partial oxidation of methane in short residence time rhodium coated monolithic reactors offers an attractive route for syngas production. The plug flow and boundary layer flow approximations are considered as computationally efficient substitutes for the full Navier-Stokes model of the reactor while including detailed heterogeneous and homogeneous chemistry. The one dimensional plug flow model has trivial computational demands but only a limited range of application. The boundary layer model provides an excellent, computationally manageable substitute for the full Navier-Stokes model over a wide range of operating conditions. Using the 38-step elementary surface reaction mechanism...
Comparison of interface capturing methods in two phase flow
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 29, Issue 6 , 2005 , Pages 539-548 ; 03601307 (ISSN) ; Jahanbakhsh, E ; Seif, M. S ; Sharif University of Technology
2005
Abstract
In two phase flow investigation, there is a need for robust methods capable of predicting interfaces, in addition to treating the traditional governing equations of fluid mechanics (Navier-Stokes Eqs.). Such methods in a finite volume approach can be classified into two typical categories called interface tracking and interface capturing methods. According to their abilities, interface capturing methods are of more interest in free surface modeling, especially when complex interface topologies such as wave breaking are included. These methods solve a scalar transport equation in order to find the distribution of two phases all over the computational domain. That is, all properties of the...
Computational simulation of marangoni convection under microgravity condition
, Article Scientia Iranica ; Volume 16, Issue 6 B , 2009 , Pages 513-524 ; 10263098 (ISSN) ; Taeibi Rahni, M ; Asadi, B ; Ahmadi, G ; Sharif University of Technology
2009
Abstract
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...
Co-sintering of M2/17-4PH powders for fabrication of functional graded composite layers
, Article Journal of Composite Materials ; Volume 44, Issue 4 , 2010 , Pages 417-435 ; 00219983 (ISSN) ; Simchi, A ; Sharif University of Technology
2010
Abstract
Stepwise-graded composite layer of M2 tool stel and 17-4PH stainless steel was fabricated by a simple powder layering technique and the isothermal and nonisothermal sintering response of the bilayer were examined. It was shown that the materials exhibit poor compatibility during co-sintering, i.e., the amount of mismatch shrinkage is significant. An improved compatibility was obtained by adding 0.2 wt% B to the stainless steel powder. Formation of relatively dense layer at the bonding zone indicated an enhanced densification rate at the interface. Microstructural studies showed formation of a ferritic interface in M2/17-4PH composite and elongated grains with an intergranular boride phase...
Cosintering of powder injection molding parts made from ultrafine WC-Co and 316L stainless steel powders for fabrication of novel composite structures
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 41, Issue 1, January 2010, Pages 233-241 ; Petzoldt, F ; Sharif University of Technology
Abstract
Abstract Sintering response and phase formation during sintering of WC-Co/316L stainless steel composites produced by assembling of powder injection molding (PIM) parts were studied. It is shown that during cosintering a significant mismatch strain (> 4 pct) is developed in the temperature range of 1080° C to 1350° C. This mismatch strain induces biaxial stresses at the interface, leading to interface delamination. Experimental results revealed that sintering at a heating rate of 20 K/min could be used to decrease the