Search for: phase-interfaces
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    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) Panahi, R ; Jahanbakhsh, E ; Seif, M. S ; Sharif University of Technology
    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... 

    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 Simchi, A. (Abdolreza) ; Petzoldt, F ; Sharif University of Technology
    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  

    The gas-oil interfacial behavior during gas injection into an asphaltenic oil reservoir

    , Article Journal of Chemical and Engineering Data ; Volume 58, Issue 9 , 2013 , Pages 2513-2526 ; 00219568 (ISSN) Escrochi, M ; Mehranbod, N ; Ayatollahi, S ; Sharif University of Technology
    Oil displacement and recovery efficiency during gas injection depends on the competition between driving forces and capillary resistance that is governed by gas-oil interfacial behavior. Detailed study of the interfacial forces during gas injection is the main objective of this research work. The effects of injecting gas composition and the possibility of asphaltene precipitation in a wide pressure range were determined through comprehensive experimental study. This was performed by measurement of interfacial tension of a highly asphaltenic Iranian crude oil in three surrounding gas mediums. The results showed that as pressure increases, the rate to reach miscibility reduces in the vicinity... 

    Effects of elastic contributions on the evolution of nano-structure Al3Sc phase: A phase-field study

    , Article Scientia Iranica ; Volume 23, Issue 3 , 2016 , Pages 1539-1547 ; 10263098 (ISSN) Ebrahimi, Z ; Ebrahimi, H ; Sharif University of Technology
    Sharif University of Technology  2016
    A micromechanical phase-field model is utilized to study the evolution of nanostructure Al3Sc phase in Al-Sc alloy. We study the formation of Al3Sc precipitates in an Al-Sc alloy by using an elastic phase-field model. Since the precipitates of Al3Sc phase are fully coherent with the Al matrix, the elastic energy will have an inuence on the resulting morphology. We have studied the effects of elastic strain energies on shape evolution of Al3Sc phase, numerically. The simulated nano-structures evolve from spherical to cubic shapes. The equilibrium shape of the coherent Al3Sc phase is found to be determined by minimizing the sum of the elastic and interfacial energies through the phase-field... 

    Phase field approach for nanoscale interactions between crack propagation and phase transformation

    , Article Nanoscale ; Volume 11, Issue 46 , 2019 , Pages 22243-22247 ; 20403364 (ISSN) Jafarzadeh, H ; Levitas, V. I ; Farrahi, G. H ; Javanbakht, M ; Sharif University of Technology
    Royal Society of Chemistry  2019
    The phase field approach (PFA) for the interaction of fracture and martensitic phase transformation (PT) is developed, which includes the change in surface energy during PT and the effect of unexplored scale parameters proportional to the ratio of the widths of the crack surface and the phase interface, both at the nanometer scale. The variation of these two parameters causes unexpected qualitative and quantitative effects: shift of PT away from the crack tip, "wetting" of the crack surface by martensite, change in the structure and geometry of the transformed region, crack trajectory, and process of interfacial damage evolution, as well as transformation toughening. The results suggest... 

    Solute redistribution during transient liquid phase bonding of IN738LC with BNi-3 interlayer

    , Article Materials Science and Technology ; Volume 24, Issue 4 , 2008 , Pages 449-456 ; 02670836 (ISSN) Mosallaee, M ; Ekrami, A ; Ohsasa, K ; Matsuura, K ; Sharif University of Technology
    Redistribution of alloying elements in the transient liquid phase (TLP) bonding zone of IN738LC/ BNi-3/IN738LC was studied to investigate microstructural evolution in this area. Wavelength dispersive spectrometry and electron probe microanalysis revealed that, during non-isothermal solidification in the TLP bonding zone, enrichment of residual liquid phase with the positive segregating elements caused formation of intermetallic in the bonding zone. Scanning electron microscopy observation Indicated that the redistribution of alloying elements, between TLP bonding zone and base alloy, resulted In formation of a γ′ boundary layer, containing high density of fine γ′, around the bonding zone.... 

    Two-dimensional numerical solution of steady withdrawal from the lens of freshwater in a tropical island

    , 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) Jabbari, E ; Haji Mohammadi, M ; Saeedpanah, I ; Sharif University of Technology
    The work presented here is a study of the steady withdrawal of water from the lens of freshwater situated above the ocean's salt water and within the island. It is the aim of this paper to investigate the process of withdrawal from the lens of freshwater with a view to establishing the critical flow values for withdrawal and the effects of sink location and density differences on these values, and also to determine the effects of relative density differences. Steady solutions are found for the shape of the interface between salt and freshwater beneath a tropical island. A Green_s function approach is used and proves to be much more robust than spectral methods. Computations of the surface... 

    Densification and microstructural evolution during co-sintering of Ni-base superalloy powders

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 37, Issue 8 , 2006 , Pages 2549-2557 ; 10735623 (ISSN) Simchi, A ; Sharif University of Technology
    This work presents the effect of co-sintering on the densification and microstructural evolution in the two-layer stepwise graded composite of INCONEL 718 and INCONEL 625 superalloys. A pressureless co-sintering method in conjunction with a powder layering technique was used. The sintering was carried out in solid state and liquid phase in temperature ranging from 1260 °C through 1300 °C for 60 minutes in a low pressure of an argon atmosphere. Nonisothermal sintering behavior was also examined by dilatometric analysis. Similarly, the sintering response of the individual layers was characterized. The results reveal an enhanced densification rate during co-sintering of the composite layers.... 

    A review of concentric annular heat pipes

    , Article Heat Transfer Engineering ; Volume 26, Issue 6 , 2005 , Pages 45-58 ; 01457632 (ISSN) Nouri Borujerdi, A ; Layeghi, M ; Sharif University of Technology
    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... 

    Torsion of an eccentrically two-phase circular nanobar

    , Article 2010 IEEE 5th International Conference on Nano/Micro Engineered and Molecular Systems, NEMS 2010, 20 January 2010 through 23 January 2010 ; January , 2010 , Pages 70-73 ; 9781424465439 (ISBN) Pahlevani, L ; Shodja, H. M ; Sharif University of Technology
    The effect of surface and interface elasticity in analysis of the Saint-Venant torsion problem of an eccentrically two-phase circular nanobar is considered. The problem is formulated in the context of Gurtin's surface elasticity. For a rigorous solution of the proposed problem, conformal mapping together with a Laurent series expansion are employed. At the nanoscales the usual classical theories cease to hold and the corresponding results deteriorate. The numerical results well illustrate that the torsional rigidity of the mentioned nanosized structural elements are significantly affected by the size. Some applications of the given results can be contemplated in the design of micro/nano... 

    On the formation of intermetallics during the furnace brazing of pure titanium to 304 stainless steel using Ag (30-50%)-Cu filler metals

    , Article Materials and Manufacturing Processes ; Volume 25, Issue 11 , 2010 , Pages 1333-1340 ; 10426914 (ISSN) Shafiei, A ; Abachi, P ; Dehghani, K ; Pourazarang, K ; Sharif University of Technology
    In the present work, the effect of brazing pa rameters on the properties of the brazed joint of pure titanium and 304 stainless steel (304SS) was investigated. Three different Ag-Cu filler metals were used, while the temperature and time of brazing were in the range of 800-950°C and 5-45 minutes, respectively. The microstructural observations show that, depending on the brazing conditions, different intermetallic phases such as CuTi2, CuTi, Cu3Ti4, and FeTi were formed at the phases interface. Based on the microstructural observations, a model was developed to characterize the formation of phases at the interfaces and brazed joint. The results show that, while some phases may form during the... 

    The scattering of P-waves by a piezoelectric particle with FGPM interfacial layers in a polymer matrix

    , Article International Journal of Solids and Structures ; Volume 47, Issue 18-19 , 2010 , Pages 2390-2397 ; 00207683 (ISSN) Kamali, M. T ; Shodja, H. M ; Sharif University of Technology
    Propagation of P-wave in an unbounded elastic polymer medium which contains a set of nested concentric spherical piezoelectric inhomogeneities is formulated. The polymer matrix is made of Epoxy and is isotropic; each phase of the inhomogeneity is made of a different piezoelectric material and is radially polarized and has spherical isotropy. Note that the individual phases are homogeneous, and all interfaces are perfectly bonded. The scattered displacement and electric potentials in the matrix are expressed in terms of spherical wave vector functions and Legendre functions, respectively. The transmitted displacement and electric potentials within each phase of the piezoelectric particle are... 

    Relationship between wetting properties and macroscale hydrodynamics during forced gravity drainage and secondary waterflood

    , Article Petroleum Science and Technology ; Volume 28, Issue 8 , 2010 , Pages 804-815 ; 10916466 (ISSN) Rostami, B ; Kharrat, R ; Ghotbi, C ; Alipour Tabrizy, V ; Sharif University of Technology
    In order to relate the wetting properties at the pore scale to the macroscale prevailing forces, a series of experiments was performed in vertical porous media under forced gas invasion at various wettability conditions with partially spreading oil. To describe the dynamics of oil recovery in a three-phase flow condition, the downward gas flood experiments were continued by water injection from the bottom. Experimental results obtained in situations where the magnitudes of viscous, capillary, and gravity forces are comparable. We study the transition from flow configurations where the interface is stable with respect to viscous instability to flow configurations where viscous fingering... 

    Near-optimal trajectories to manage landing sequence in the vicinity of controlled aerodromes

    , Article Journal of Aircraft ; Volume 47, Issue 1 , 2010 , Pages 129-140 ; 00218669 (ISSN) Malaek, S. M ; Nabavi, S. Y ; Sharif University of Technology
    A comprehensive approach is proposed to manage landing sequences and their associated trajectories for an arbitrary number of aircraft in the vicinity of a controlled aerodrome. The current approach, similar to that of "first come, first served," could consider different types of priorities as well as emergencies. The approach is especially useful to combine unstructured free-flight trajectories with structured ones during the approach phase of the flight A comprehensive cost function considers the relative size of all aircraft together with their relative speeds and flight directions. This helps optimize the amount of fuel consumption while respecting separation minima. Resulting... 

    Examination of a solar desalination system equipped with an air bubble column humidifier, evacuated tube collectors and thermosyphon heat pipes

    , Article Desalination ; Volume 397 , 2016 , Pages 30-37 ; 00119164 (ISSN) Behnam, P ; Behshad Shafii, M ; Sharif University of Technology
    In this paper, the performance of a novel HDH solar desalination system equipped with a combination of heat pipe (HP), evacuated tube collector (ETC) and air bubble column humidifier is experimentally investigated. This novel HDH system uses advantages of ETC-HP as a highly efficient thermal absorption and conductor device, and at the same time employs the advantages of an air bubble column humidifier, i.e. high interface area and effective mixing in order to heat the water and humidify the air, respectively. The effects of various parameters including incoming air flow rate into the humidifier, initial depth of water in the humidifier, and adding fluids such as oil and water in the space... 

    Simplified model for polyurethane foaming in porous media

    , Article International Journal of Numerical Methods for Heat and Fluid Flow ; Volume 27, Issue 1 , 2017 , Pages 142-155 ; 09615539 (ISSN) Sadrhosseini, H ; Bazkhane, S ; Sharif University of Technology
    Emerald Group Publishing Ltd  2017
    Purpose - The purpose of the study is to present a simplified model to replace the complicated foaming simulations for investigating the liquid polyurethane behavior just before solidification. Design/methodology/approach - This model is inspired from the traveling heater method of crystallization because of the low injection velocity. Besides, the heat generated during the reaction is considered as a heat source function in the energy equation. Findings - Various distributions of the heat generation function inside the geometry have been studied to choose the most realistic one. Effect of parameters such as the soil material and porosity on the temperature distribution and flow field are... 

    On the phase field modeling of crack growth and analytical treatment on the parameters

    , Article Continuum Mechanics and Thermodynamics ; 2018 , Pages 1-18 ; 09351175 (ISSN) Farrahi, G. H ; Javanbakht, M ; Jafarzadeh, H ; Sharif University of Technology
    Springer New York LLC  2018
    A thermodynamically consistent phase field model for crack propagation is analyzed. The thermodynamic driving force for the crack propagation is derived based on the laws of thermodynamics. The Helmholtz free energy satisfies the thermodynamic equilibrium and instability conditions for the crack propagation. Analytical solutions for the Ginzburg–Landau equation including the surface profile and the estimation of the kinetic coefficient are found. It is shown how kinetic coefficient affects the local stress field. The local critical stress for the crack propagation is calibrated with the theoretical strength which gives the value of the crack surface width. The finite element method is... 

    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) Ahmadijokani, F ; Ahmadipouya, S ; Molavi, H ; Arjmand, M ; Sharif University of Technology
    Royal Society of Chemistry  2019
    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... 

    Investigation of structural and mechanical properties of magnetic pulse welded dissimilar aluminum alloys

    , Article Journal of Manufacturing Processes ; Volume 37 , 2019 , Pages 292-304 ; 15266125 (ISSN) Pourabbas, M ; Abdollah zadeh, A ; Sarvari, M ; Pouranvari, M ; Miresmaeili, R ; Sharif University of Technology
    Elsevier Ltd  2019
    The present study aimed to join AA4014 to AA7075 by using magnetic pulse welding (MPW). In addition, acceptable joints were achieved by selecting welding parameters such as collision angle and discharge energy appropriately. Changing collision angle and discharge energy can influence the velocity, leading to the formation of three different types of welding interfaces with wavy, molten wavy and porous morphologies. The formation of these various morphologies is mainly associated with different collision angle parameters. The hardness of the welding interface with molten layer was significantly higher than that of the base metals due to the grain refinement phenomenon occurring through the... 

    Investigation of iron ore particle size and shape on green pellet quality

    , Article Canadian Metallurgical Quarterly ; Volume 59, Issue 2 , 2020 , Pages 242-250 Abazarpoor, A ; Halali, M ; Hejazi, R ; Saghaeian, M ; Sheikh Zadeh, V ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Particle size and shape of iron ore concentrate are effective parameters in the production of quality green pellets. In this research, the effect of particle morphology on green pellet quality was studied. It was concluded that pellet quality improved with increasing specific surface area. Drop number and green compression strength of pellets ground by HPGR were found to be superior over those ground in the ball mill. The chief reasons were related to particle shape and the fraction of fine particles. Smaller particle size results in a higher order of bonding between particles and therefore the formation of a stronger system. Also, the rougher and less circular shape of particles resulted in...