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    A review of thermal conductivity of various nanofluids

    , Article Journal of Molecular Liquids ; Volume 265 , 2018 , Pages 181-188 ; 01677322 (ISSN) Ahmadi, M. H ; Mirlohi, A ; Alhuyi Nazari, M ; Ghasempour, R ; Sharif University of Technology
    Abstract
    In the present paper, several experimental and theoretical studies conducted on the thermal conductivity of nanofluids are represented and investigated. Based on the reviewed studies, various factors affect thermal conductivity of nanofluids such as temperature, the shape of nanoparticles, concentration and etc. Results indicated the increase in temperature and concentration of nanoparticles usually leads to the higher thermal conductivity of nanofluids. In addition, it is concluded that there are some novel approaches in order to obtain nanofluids with more appropriate thermal properties including using binary fluids as the base fluid or utilizing hybrid nanofluids. © 2018 Elsevier B.V  

    First-passage-time processes and subordinated Schramm-Loewner evolution

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 84, Issue 1 , July , 2011 ; 15393755 (ISSN) Nezhadhaghighi, M. G ; Rajabpour, M. A ; Rouhani, S ; Sharif University of Technology
    2011
    Abstract
    We study the first-passage-time processes of the anomalous diffusion on the self-similar curves in two dimensions. The scaling properties of the mean-square displacement and mean first passage time of the fractional Brownian motion and subordinated walk on the different fractal curves (loop-erased random walk, harmonic explorer, and percolation front) are derived. We also define natural parametrized subordinated Schramm-Loewner evolution (NS-SLE) as a mathematical tool that can model diffusion on fractal curves. The scaling properties of the mean-square displacement and mean first passage time for NS-SLE are obtained by numerical means  

    Complex self-propelled rings: A minimal model for cell motility

    , Article Soft Matter ; Volume 13, Issue 35 , 2017 , Pages 5865-5876 ; 1744683X (ISSN) Abaurrea Velasco, C ; Dehghani Ghahnaviyeh, S ; Nejat Pishkenari, H ; Auth, T ; Gompper, G ; Sharif University of Technology
    Royal Society of Chemistry  2017
    Abstract
    Collective behavior of active matter is observed for self-propelled particles, such as vibrated disks and active Brownian particles, as well as for cytoskeletal filaments in motile cells. Here, a system of quasi two-dimensional penetrable self-propelled rods inside rigid rings is used to construct a complex self-propelled particle. The rods interact sterically with each other and with a stationary or mobile ring via a separation-shifted Lennard-Jones potential. They either have a sliding attachment to the inside of the ring at one of their ends, or can move freely within the ring confinement. We study the inner structure and dynamics of the mobile self-propelled rings. We find that these... 

    Modified Buongiorno's model for fully developed mixed convection flow of nanofluids in a vertical annular pipe

    , Article Computers and Fluids ; Vol. 89 , 2014 , pp. 124-132 ; ISSN: 00457930 Malvandi, A ; Moshizi, S. A ; Soltani, E. G ; Ganji, D. D ; Sharif University of Technology
    Abstract
    This paper deals with the mixed convective heat transfer of nanofluids through a concentric vertical annulus. Because of the non-adherence of the fluid-solid interface in the presence of nanoparticle migrations, known as slip condition, the Navier's slip boundary condition was considered at the pipe walls. The employed model for nanofluid includes the modified two-component four-equation non-homogeneous equilibrium model that fully accounts for the effects of nanoparticles volume fraction distribution. Assuming the fully developed flow and heat transfer, the basic partial differential equations including continuity, momentum, and energy equations have been reduced to two-point ordinary... 

    Analysis of nanoparticles migration on natural convective heat transfer of nanofluids

    , Article International Journal of Thermal Sciences ; Volume 68 , June , 2013 , Pages 79-93 ; 12900729 (ISSN) Pakravan, H. A ; Yaghoubi, M ; Sharif University of Technology
    2013
    Abstract
    Both experimental and numerical studies are unanimous for enhancing Nusselt number for forced convection of nanofluids with slight difference, but there is inconsistency for natural convection heat transfer of nanofluids. In this paper attempt is made to study the effects of nanoparticles migration on the natural convection behavior of nanofluids. For analysis, a mixture model is used by including important phenomena such as Brownian motion and thermophoresis effects. These two mechanisms are taken into account to compute the slip velocities between the base fluid and nanoparticles. The governing equations are solved numerically and good agreements are observed in comparison with... 

    Avalanche frontiers in the dissipative Abelian sandpile model and off-critical Schramm-Loewner evolution

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 85, Issue 5 , 2012 ; 15393755 (ISSN) Najafi, M. N ; Moghimi Araghi, S ; Rouhani, S ; Sharif University of Technology
    2012
    Abstract
    Avalanche frontiers in Abelian sandpile model (ASM) are random simple curves whose continuum limit is known to be a Schramm-Loewner evolution with diffusivity parameter κ=2. In this paper we consider the dissipative ASM and study the statistics of the avalanche and wave frontiers for various rates of dissipation. We examine the scaling behavior of a number of functions, such as the correlation length, the exponent of distribution function of loop lengths, and the gyration radius defined for waves and avalanches. We find that they do scale with the rate of dissipation. Two significant length scales are observed. For length scales much smaller than the correlation length, these curves show... 

    Study of heterogeneity loss in upscaling of geological maps by introducing a cluster-based heterogeneity number

    , Article Physica A: Statistical Mechanics and its Applications ; Volume 436 , October , 2015 , Pages 1-13 ; 03784371 (ISSN) Ganjeh Ghazvini, M ; Masihi, M ; Baghalha, M ; Sharif University of Technology
    Elsevier  2015
    Abstract
    The prediction of flow behavior in porous media can provide useful insights into the mechanisms involved in CO2 sequestration, petroleum engineering and hydrology. The multi-phase flow is usually simulated by solving the governing equations over an efficient model. The geostatistical (or fine grid) models are rarely used for simulation purposes because they have too many cells. A common approach is to coarsen a fine gird realization by an upscaling method. Although upscaling can speed up the flow simulation, it neglects the fine scale heterogeneity. The heterogeneity loss reduces the accuracy of simulation results. In this paper, the relation between heterogeneity loss during upscaling and... 

    Discrete scale invariance and stochastic Loewner evolution

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; 2010 , Volume 82, Issue 6 ; 15393755 (ISSN) Ghasemi Nezhadhaghighi, M ; Rajabpour, M. A ; Sharif University of Technology
    2010
    Abstract
    In complex systems with fractal properties the scale invariance has an important rule to classify different statistical properties. In two dimensions the Loewner equation can classify all the fractal curves. Using the Weierstrass-Mandelbrot (WM) function as the drift of the Loewner equation we introduce a large class of fractal curves with discrete scale invariance (DSI). We show that the fractal dimension of the curves can be extracted from the diffusion coefficient of the trend of the variance of the WM function. We argue that, up to the fractal dimension calculations, all the WM functions follow the behavior of the corresponding Brownian motion. Our study opens a way to classify all the... 

    Dynamics of magnetic nano-flake vortices in Newtonian fluids

    , Article Journal of Magnetism and Magnetic Materials ; Volume 419 , 2016 , Pages 547-552 ; 03048853 (ISSN) Bazazzadeh, N ; Mohseni, S. M ; Khavasi, A ; Zibaii, M. I ; Movahed, S. M. S ; Jafari, G. R ; Sharif University of Technology
    Elsevier 
    Abstract
    We study the rotational motion of nano-flake ferromagnetic disks suspended in a Newtonian fluid, as a potential material owing the vortex-like magnetic configuration. Using analytical expressions for hydrodynamic, magnetic and Brownian torques, the stochastic angular momentum equation is determined in the dilute limit conditions under applied magnetic field. Results are compared against experimental ones and excellent agreement is observed. We also estimate the uncertainty in the orientation of the disks due to the Brownian torque when an external magnetic field aligns them. Interestingly, this uncertainty is roughly proportional to the ratio of thermal energy of fluid to the magnetic energy... 

    Comprehensive reactive receiver modeling for diffusive molecular communication systems: reversible binding, molecule degradation, and finite number of receptors

    , Article IEEE Transactions on Nanobioscience ; Volume PP, Issue 99 , 2016 ; 15361241 (ISSN) Ahmadzadeh, A ; Arjmandi, H ; Burkovski, A ; Schober, R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    This paper studies the problem of receiver modeling in molecular communication systems. We consider the diffusive molecular communication channel between a transmitter nanomachine and a receiver nano-machine in a fluid environment. The information molecules released by the transmitter nano-machine into the environment can degrade in the channel via a first-order degradation reaction and those that reach the receiver nanomachine can participate in a reversible bimolecular reaction with receiver receptor proteins. Thereby, we distinguish between two scenarios. In the first scenario, we assume that the entire surface of the receiver is covered by receptor molecules. We derive a closed-form... 

    Effects of Brownian motions and thermophoresis diffusions on the hematocrit and LDL concentration/diameter of pulsatile non-Newtonian blood in abdominal aortic aneurysm

    , Article Journal of Non-Newtonian Fluid Mechanics ; Volume 294 , 2021 ; 03770257 (ISSN) Abbasi, M ; Esfahani, A. N ; Golab, E ; Golestanian, O ; Ashouri, N ; Sajadi, S. M ; Ghaemi, F ; Baleanu, D ; Karimipour, A ; Sharif University of Technology
    Elsevier B.V  2021
    Abstract
    LDL concentration is believed to be responsible for plaque formation that leads to atherosclerotic cardiovascular disease. We conducted this study to investigate the effects of hematocrits and LDL diameters on LDL concentration on the wall of an abdominal aortic aneurysm (AAA). The blood flow was considered to be a pulsatile and non-Newtonian flow whose viscosity was a function of hematocrits and strain rate. Lumen, Brownian, and thermophoresis diffusions were analyzed in LDL concentration. The results demonstrated that adding thermophoresis diffusion increases LDL concentration. Moreover, among three types of LDLs, including small LDLs, intermediate LDLs, and large LDLs, small LDLs were the... 

    Effects of Brownian motions and thermophoresis diffusions on the hematocrit and LDL concentration/diameter of pulsatile non-Newtonian blood in abdominal aortic aneurysm

    , Article Journal of Non-Newtonian Fluid Mechanics ; Volume 294 , 2021 ; 03770257 (ISSN) Abbasi, M ; Esfahani, A. N ; Golab, E ; Golestanian, O ; Ashouri, N ; Sajadi, S. M ; Ghaemi, F ; Baleanu, D ; Karimipour, A ; Sharif University of Technology
    Elsevier B.V  2021
    Abstract
    LDL concentration is believed to be responsible for plaque formation that leads to atherosclerotic cardiovascular disease. We conducted this study to investigate the effects of hematocrits and LDL diameters on LDL concentration on the wall of an abdominal aortic aneurysm (AAA). The blood flow was considered to be a pulsatile and non-Newtonian flow whose viscosity was a function of hematocrits and strain rate. Lumen, Brownian, and thermophoresis diffusions were analyzed in LDL concentration. The results demonstrated that adding thermophoresis diffusion increases LDL concentration. Moreover, among three types of LDLs, including small LDLs, intermediate LDLs, and large LDLs, small LDLs were the... 

    Thermal conductivity of mixed nanofluids under controlled pH conditions

    , Article International Journal of Thermal Sciences ; Volume 74 , 2013 , Pages 63-71 ; 12900729 (ISSN) Iranidokht, V ; Hamian, S ; Mohammadi, N ; Shafii, M. B ; Sharif University of Technology
    2013
    Abstract
    Just a few investigations have been conducted to study the mixed nanofluids(MNs), which contain more than one type of nanoparticles, despite considerable advances in the field of nanofluids thermal conductivity. In present research, by combining different volume fractions of various nanoparticles, the variation of mixed nanofluids thermal conductivity was considered. The mentioned nanofluids have different fabrication cost. First, the effect of each specific nanoparticle presence in the base fluid on the thermal conductivity of nanofluid was surveyed both experimentally and theoretically. Then, the thermal conductivities of two MNs, one consisted of a metallic nanoparticle (high thermal... 

    Long-lived and unstable modes of Brownian suspensions in microchannels

    , Article Journal of Fluid Mechanics ; Volume 701 , 2012 , Pages 407-418 ; 00221120 (ISSN) Khoshnood, A ; Jalali, M. A ; Sharif University of Technology
    2012
    Abstract
    We investigate the stability of the pressure-driven, low-Reynolds-number flow of Brownian suspensions with spherical particles in microchannels. We find two general families of stable/unstable modes: (i) degenerate modes with symmetric and antisymmetric patterns; (ii) single modes that are either symmetric or antisymmetric. The concentration profiles of degenerate modes have strong peaks near the channel walls, while single modes diminish there. Once excited, both families would be detectable through high-speed imaging. We find that unstable modes occur in concentrated suspensions whose velocity profiles are sufficiently flattened near the channel centreline. The patterns of growing unstable... 

    Investigation of particle dispersion and deposition in a channel with elliptic obstructions using lattice Boltzmann method

    , Article 2012 7th IEEE International Conference on Nano/Micro Engineered and Molecular Systems, NEMS 2012, 5 March 2012 through 8 March 2012 ; March , 2012 , Pages 523-528 ; 9781467311243 (ISBN) Tehrani, A ; Moosavi, A ; Sharif University of Technology
    2012
    Abstract
    Particle transport and deposition in a channel flow with elliptic obstruction is studied. Numerical simulation of fluid flow is performed using two-dimensional lattice Boltzmann method, while one-way coupling Lagrangian method for particle tracking is used. Standard particles are injected in the inlet of the channel. Gravity, Drag force, Brownian forces, and the Saffman lift are considered in equation of particle motion. The influence of geometrical parameter, ellipse aspect ratio, is studied on dispersion and deposition of particles as well as the flow parameters, such as Reynolds number. In addition, the effect of particles size -particles of 0.01-10μm in diameter- on dispersion and... 

    Analysis of nanofluid heat transfer in parallel-plate vertical channels partially filled with porous medium

    , Article International Journal of Thermal Sciences ; Volume 55 , 2012 , Pages 103-113 ; 12900729 (ISSN) Hajipour, M ; Molaei Dehkordi, A ; Sharif University of Technology
    Abstract
    In this article, mixed-convective heat transfer of nanofluids in a vertical channel partially filled with highly porous medium was studied. In the porous region, the Brinkman-Forchheimer extended Darcy model was used to describe the fluid flow pattern. Different viscous dissipation models were also applied to account for viscous heating. At the porous medium-fluid interface, interfacial coupling conditions for the fluid velocity and temperature were used to derive the analytical solution using a two-parameter perturbation method. The model used for the nanofluids incorporates the effects of Brownian motion and thermophoresis. With constant wall temperature, velocity and temperature profiles... 

    Heat transfer and pressure drop characteristics of nanofluid in unsteady squeezing flow between rotating porous disks considering the effects of thermophoresis and Brownian motion

    , Article Advanced Powder Technology ; Volume 27, Issue 2 , March , 2016 , Pages 564–574 ; 09218831 (ISSN) Saidi, M. H ; Tamim, H ; Sharif University of Technology
    Elsevier  2016
    Abstract
    In this study, the unsteady three dimensional nanofluid flow, heat and mass transfer in a rotating system in the presence of an externally applied uniform vertical magnetic field is investigated. This study has different applications in rotating magneto-hydrodynamic (MHD) energy generators for new space systems and also thermal conversion mechanisms for nuclear propulsion space vehicles. The important effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The governing equations are non-dimensionalized using geometrical and physical flow field-dependent parameters. The velocity profiles in radial, tangential and axial directions, pressure gradient,... 

    Natural convection of Al2O3-water nanofluid in an inclined enclosure with the effects of slip velocity mechanisms: Brownian motion and thermophoresis phenomenon

    , Article International Journal of Thermal Sciences ; Volume 105 , 2016 , Pages 137-158 ; 12900729 (ISSN) Esfandiary, M ; Mehmandoust, B ; Karimipour, A ; Pakravan, H. A ; Sharif University of Technology
    Elsevier Masson SAS 
    Abstract
    Effects of inclination angle on natural convective heat transfer and fluid flow in an enclosure filled with Al2O3-water nanofluid are studied numerically. The left and right walls of enclosure are kept in hot and cold constant temperature while the other two walls are assumed to be adiabatic. Considering Brownian motion and thermophoresis effect (two important slip velocity mechanisms) the two-phase mixture model has been employed to investigate the flow and thermal behaviors of the nanofluid. The study was performed for various inclination angles of enclosure ranging from γ = 0° to γ = 60°, volume fraction from 0% to 3%, and Rayleigh numbers varying from 105 to 107. The governing equations... 

    Heat transfer and pressure drop characteristics of nanofluid in unsteady squeezing flow between rotating porous disks considering the effects of thermophoresis and Brownian motion

    , Article Advanced Powder Technology ; Volume 27, Issue 2 , Volume 27, Issue 2 , 2016 , Pages 564-574 ; 09218831 (ISSN) Saidi, M. H ; Tamim, H ; Sharif University of Technology
    Elsevier B.V  2016
    Abstract
    In this study, the unsteady three dimensional nanofluid flow, heat and mass transfer in a rotating system in the presence of an externally applied uniform vertical magnetic field is investigated. This study has different applications in rotating magneto-hydrodynamic (MHD) energy generators for new space systems and also thermal conversion mechanisms for nuclear propulsion space vehicles. The important effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The governing equations are non-dimensionalized using geometrical and physical flow field-dependent parameters. The velocity profiles in radial, tangential and axial directions, pressure gradient,... 

    Margination and adhesion of micro- and nanoparticles in the coronary circulation: a step towards optimised drug carrier design

    , Article Biomechanics and Modeling in Mechanobiology ; 2017 , Pages 1-17 ; 16177959 (ISSN) Forouzandehmehr, M ; Shamloo, A ; Sharif University of Technology
    Abstract
    Obstruction of left anterior descending artery (LAD) due to the thrombosis or atherosclerotic plaques is the leading cause of death worldwide. Targeted delivery of drugs through micro- and nanoparticles is a very promising approach for developing new strategies in clot-busting or treating restenosis. In this work, we modelled the blood flow characteristics in a patient-specific reconstructed LAD artery by the fluid–solid interaction method and based on physiological boundary conditions. Next, we provided a Lagrangian description of micro- and nanoparticles dynamics in the blood flow considering their Brownian motion and the particle–particle interactions. Our results state that the number of...