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Pure axial flow of viscoelastic fluids in rectangular microchannels under combined effects of electro-osmosis and hydrodynamics
, Article Theoretical and Computational Fluid Dynamics ; 2017 , Pages 1-21 ; 09354964 (ISSN) ; Saidi, M. H ; Ebrahimi, A ; Sharif University of Technology
Abstract
This paper presents an analysis of the combined electro-osmotic and pressure-driven axial flows of viscoelastic fluids in a rectangular microchannel with arbitrary aspect ratios. The rheological behavior of the fluid is described by the complete form of Phan-Thien–Tanner (PTT) model with the Gordon–Schowalter convected derivative which covers the upper convected Maxwell, Johnson–Segalman and FENE-P models. Our numerical simulation is based on the computation of 2D Poisson–Boltzmann, Cauchy momentum and PTT constitutive equations. The solution of these governing nonlinear coupled set of equations is obtained by using the second-order central finite difference method in a non-uniform grid...
HPGR effect on the particle size and shape of iron ore pellet feed using response surface methodology
, Article Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy ; 2017 , Pages 1-9 ; 03719553 (ISSN) ; Halali, M ; Hejazi, R ; Saghaeian, M ; Sharif University of Technology
Taylor and Francis Ltd
2017
Abstract
In this study the effect of HPGR operational parameters on the dimensional properties of pellet feed was examined and optimized using factorial methodology. The operational parameters considered include feed moisture, specific pressure and roll speed. For this study, size and shape of particles with Blaine number in the range 1800–2200 cm2 g−1 was thoroughly investigated. It was deduced that increasing the specific pressure and decreasing the roll speed would result in reduction of D80 but would increase the Blaine number. The circularity, aspect ratio and roughness descriptors of the particles were measured by SEM micrographs and image analysis software. It was observed that particles...
Fully-coupled mathematical modeling of actomyosin-cytosolic two-phase flow in a highly deformable moving Keratocyte cell
, Article Journal of Biomechanics ; 2017 ; 00219290 (ISSN) ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
Interaction between intracellular dynamics and extracellular matrix (ECM) generally occurred into very thin fragment of moving cell, namely lamellipodia, enables all movable cells to crawl on ECM. In fast-moving cells such as fish Keratocytes, Lamellipodia including most cell area finds a fan-like shape during migration, with a variety of aspect ratio function of fish type. In this work, our purpose is to present a novel and more complete two-dimensional continuum mathematical model of actomyosin-cytosolic two-phase flow of a self-deforming Keratocyte with circular spreaded to steady fan-like shape. In the new approach, in addition to the two-phase flow of the F-actin and cytosol, the...
Optimization of the heat transfer coefficient and pressure drop of Taylor-Couette-Poiseuille flows between an inner rotating cylinder and an outer grooved stationary cylinder
, Article International Journal of Heat and Mass Transfer ; Volume 108 , 2017 , Pages 1449-1459 ; 00179310 (ISSN) ; Nakhchi, M. E ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
The aim of this study is to find optimum values of design parameters of annular flow with outer grooved cylinder and rotating inner cylinder in the presence of axial flow by using Response surface Method (RSM). This configuration is popular in cooling of electric generators and rotating machineries. Groove aspect ratio (0
Three-dimensional numerical simulation of a novel electroosmotic micromixer
, Article Chemical Engineering and Processing: Process Intensification ; Volume 119 , 2017 , Pages 25-33 ; 02552701 (ISSN) ; Madadelahi, M ; Abdorahimzadeh, S ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Lab-on-a-chip (LOC) systems have been widely used in chemical and medical analyses. In this study, a novel T-shaped electroosmotic micromixer was simulated and the effects of different parameters on the mixing process were examined. These parameters include; inlet angle, number of conducting hurdles, arrangements of the hurdles, geometry of hurdles and chambers, aspect ratios of the channel cross-sectional profile, hurdle radius, and depth. It was found that the inlet angle has a direct influence on mixing index (σ). The effect of various number of hurdles (one, two, three and four hurdles) and their orientations was investigated. Simulations revealed that using two conducting hurdles is the...
Evaluation of planing craft maneuverability using mathematical modeling under the action of the rudder
, Article Scientia Iranica ; Volume 24, Issue 1 , 2017 , Pages 293-301 ; 10263098 (ISSN) ; Seif, M. S ; Mehdigholi, H ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
In the recent years, different mathematical models have been suggested for maneuvering of displacement vessels, which are capable to estimate maneuvering of the vessel with acceptable precision. But, simulation of planing craft maneuverability through a mathematical model has not been developed yet. In this paper, a mathematical model is developed for maneuvering of the planing craft by including the rudder forces and moments. Different maneuvers, such as straight-line stability, course keeping, and turning circle, are executed through the mathematical model. Simulation results are validated with the published experimental results and it is shown that they are in good agreement. Finally, the...
Heat transfer enhancement in annular flow with outer grooved cylinder and rotating inner cylinder: review and experiments
, Article Applied Thermal Engineering ; Volume 120 , 2017 , Pages 257-268 ; 13594311 (ISSN) ; Nakhchi, M. E ; Sharif University of Technology
Abstract
This experimental work is an attempt to identify the most significant parameters influencing heat transfer enhancement in annular flow with outer grooved cylinder and rotating inner cylinder. This type of flow known as Taylor-Couette flow has many industrial applications such as electrical power generators and rotating machineries. A comprehensive review of the previous works on flow regimes, heat transfer and pressure drop in grooved channels is provided. The experiments are conducted based on four different factors including Taylor number, 0
Analytical determination of shear correction factor for Timoshenko beam model
, Article Steel and Composite Structures ; Volume 29, Issue 4 , 2018 , Pages 483-491 ; 12299367 (ISSN) ; Faghidian, S. A ; Shodja, H. M ; Sharif University of Technology
Techno Press
2018
Abstract
Timoshenko beam model is widely exploited in the literature to examine the mechanical behavior of stubby beam-like components. Timoshenko beam theory is well-known to require the shear correction factor in order to recognize the non-uniform shear distribution at a section. While a variety of shear correction factors are appeared in the literature so far, there is still no consensus on the most appropriate form of the shear correction factor. The Saint-Venant's flexure problem is first revisited in the frame work of the classical theory of elasticity and a highly accurate approximate closed-form solution is presented employing the extended Kantorovich method. The resulted approximate solution...
Scattering of SH-waves by an elliptic cavity/crack beneath the interface between functionally graded and homogeneous half-spaces via multipole expansion method
, Article Journal of Sound and Vibration ; Volume 435 , 2018 , Pages 372-389 ; 0022460X (ISSN) ; Shodja, H. M ; Sharif University of Technology
Academic Press
2018
Abstract
In this study, based on multipole expansion method an analytical treatment is presented for the anti-plane scattering of SH-waves by an arbitrarily oriented elliptic cavity/crack which is embedded near the interface between exponentially graded and homogeneous half-spaces. The cavity is embedded within the inhomogeneous half-space. The boundary value problem of interest is solved by constructing an appropriate set of multipole functions which satisfy (i) the governing equation in each half-space, (ii) the continuity conditions across the interface between the two half-spaces, and (iii) the far-field radiation and regularity conditions. The analytical expressions for the scattered...
Experimental study of convective heat transfer in the entrance region of an annulus with an external grooved surface
, Article Experimental Thermal and Fluid Science ; Volume 98 , 2018 , Pages 557-562 ; 08941777 (ISSN) ; Nakhchi, M. E ; Sharif University of Technology
Elsevier Inc
2018
Abstract
The aim of this experimental work is to study the effect of grooved surfaces in the entrance region of annular flows on local heat transfer. The outer stationary cylinder is grooved and the inner rotating cylinder is smooth. This configuration is applicable in industrial applications such as rotating heat pipes for cooling of superconducting machines or motors rotor, electrical generators where heat generates in the grooves containing wires, transient heating of axial compressor rotor drams, combustion chamber in turbojets, air-cooled axial-flux permanent-magnet machines. The experimental tests were performed based on aspect ratio of the groove, effective Reynolds number and Taylor number....
3D buckling assessment of cylindrical steel silos of uniform thickness under seismic action
, Article Thin-Walled Structures ; Volume 131 , 2018 , Pages 654-667 ; 02638231 (ISSN) ; Maleki, S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This paper investigates the dynamic buckling behavior of steel silos subjected to horizontal base excitations. The elastic-plastic buckling resistance of three silos with different aspect ratios is estimated using Incremental Dynamic Analyses (IDA). Accordingly, the critical base shear, base moment and the peak ground acceleration (PGA) at the buckling instant are calculated. Moreover, the additional normal pressures induced from bulk solids on silo walls are evaluated and compared with those of Eurocode 8. The results obtained suggest that slender silos are more vulnerable to buckling failure, while squatter silos represent a considerably higher resistance under same seismic conditions. ©...
A novel model for analysis of multilayer graphene sheets taking into account the interlayer shear effect
, Article Meccanica ; Volume 53, Issue 11-12 , 2018 , Pages 3061-3082 ; 00256455 (ISSN) ; Asghari, M ; Sharif University of Technology
Springer Netherlands
2018
Abstract
In this study, a multiplate shear model is developed for dynamic analysis of multilayer graphene sheets with arbitrary shapes considering the interlayer shear effect. By utilizing the model, then some free-vibration analysis is presented. According to the experimental results, the weak interlayer van der Waals interaction cannot maintain the integrity of carbon atoms in adjacent layers. Therefore, it is required that the interlayer shear effect is accounted to study multilayer graphene mechanical behavior. The governing differential equation of motion is derived for the multilayer graphene sheets utilizing a variational approach based on the Kirchhoff plate model. The essential and natural...
Small-scale analysis of plates with thermoelastic damping based on the modified couple stress theory and the dual-phase-lag heat conduction model
, Article Acta Mechanica ; Volume 229, Issue 9 , 2018 , Pages 3869-3884 ; 00015970 (ISSN) ; Asghari, M ; Sharif University of Technology
Springer-Verlag Wien
2018
Abstract
Thermoelastic damping (TED) is one of the main energy dissipation mechanisms in structures with small scales. On the other hand, the classical continuum theory is not capable of describing the mechanical behavior of small-scale structures. In this paper, small-scale effects on the thermoelastic damping in microplates are studied. To this end, the coupled governing equations of motion and heat conduction are obtained based on the non-classical continuum theory of the modified couple stress and the dual-phase-lag heat conduction model. By solving these coupled equations, an explicit expression including small-scale effects for calculating TED in microplates is derived. The results are compared...
Universal rotation of nanowires in static uniform electric fields in viscous dielectric liquids
, Article Applied Physics Letters ; Volume 113, Issue 6 , 2018 ; 00036951 (ISSN) ; Esfandiar, A ; Moshfegh, A. Z ; Sharif University of Technology
American Institute of Physics Inc
2018
Abstract
The wide utilization of nanomanipulation as a promising approach in microorganisms, nanoelectromechanical systems, and assembly of nanostructures remarks the importance of nanostructures' motion in electric fields. Here, we study the rotational dynamics of metallic and non-metallic nanowires (NWs) in a static uniform electric field in viscous dielectric liquids. For metallic NWs, it has been theoretically shown that the electric field-induced rotation is practically independent of the geometrical dimensions and the electrical properties of NWs. Our experimental results for suspended silver (Ag) NWs in microscope oil are perfectly in agreement with this model. However, in the case of TiO2...
Multi-objective optimization of functionally graded materials, thickness and aspect ratio in micro-beams embedded in an elastic medium
, Article Structural and Multidisciplinary Optimization ; Volume 58, Issue 1 , July , 2018 , Pages 265-285 ; 1615147X (ISSN) ; Sina, N ; Sharif University of Technology
Springer Verlag
2018
Abstract
Optimal design of micron-scale beams as a general case is an important problem for development of micro-electromechanical devices. For various applications, the mechanical parameters such as mass, maximum deflection and stress, natural frequency and buckling load are considered in strategies of micro-manufacturing technologies. However, all parameters are not of equal importance in each operating condition but multi-objective optimization is able to select optimal states of micro-beams which have desirable performances in various micro-electromechanical devices. This paper provides optimal states of design variables including thickness, distribution parameter of functionally graded...
Effective shear modulus of solids reinforced by randomly oriented- / aligned-elliptic multi-coated nanofibers in micropolar elasticity
, Article Composites Part B: Engineering ; Volume 143 , 15 June , 2018 , Pages 197-206 ; 13598368 (ISSN) ; Shodja, H. M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Accurate estimation of the in-plane shear modulus of solids reinforced by nano-/micro-size elliptical multi-coated fibers is the focus of this paper. It is well-known that at the scales comparable to the nanoscopic length scales of the material, traditional theory of elasticity ceases to hold and, moreover, due to lack of consideration of such length scales has an innate weakness of sensing the size effect. Therefore, it is proposed to formulate and calculate the effective shear modulus of the nano-/micro-composite within micropolar theory which introduces two material characteristic lengths into the field equations. For this purpose, Mori-Tanaka theory is extended to treat nested...
Simulation of a falling droplet in a vertical channel with rectangular obstacles
, Article European Journal of Mechanics, B/Fluids ; Volume 68 , March-April , 2018 , Pages 108-117 ; 09977546 (ISSN) ; Ebrahimi, S ; Moosavi, A ; Shafii, M. B ; Kowsary, F ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Droplet microfluidic systems have attracted a large amount of research due to their numerous applications in biomedical micro-devices and drug discovery/delivery platforms. One of the most important problems in such systems is to investigate deformation, coalescence, and breakup of droplets within the channel. The present study demonstrates numerical simulation of a falling droplet subject to gravitational force in a channel with embedded rectangular obstacles. The lattice Boltzmann method incorporated using He–Chen–Zhang method for two phase flow is employed. Two rectangular obstacles with inverse aspect ratios are introduced to investigate the mechanism of breakup and deformation of the...
Newtonian and generalized Newtonian reacting flows in serpentine microchannels: pressure driven and centrifugal microfluidics
, Article Journal of Non-Newtonian Fluid Mechanics ; Volume 251 , January , 2018 , Pages 88-96 ; 03770257 (ISSN) ; Shamloo, A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
This paper presents a comprehensive 3D numerical simulation of reacting flows in micro scale dimension through centrifugal, or Lab-On-a-CD (LOCD), and pressure-driven, or Lab-On-a-Chip (LOC) devices. Three different serpentine channel configurations (rectangular, triangular and sinusoidal) are investigated. In these configurations, two chemical species enter from two inlets and according to an irreversible chemical reaction, start yielding other species. Both Newtonian and generalized Newtonian fluids are considered in the simulations and the results are compared for both LOC and LOCD devices. Besides, the effects of different parameters such as the aspect ratio of channels’ cross section,...
Experimental and analytical study of block slit damper
, Article Journal of Constructional Steel Research ; Volume 141 , February , 2018 , Pages 167-178 ; 0143974X (ISSN) ; Pournamazian Najafabadi, E ; Esmaeilpour Estekanchi, H ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This study proposes a novel type of metallic yielding damper called block slit damper or BSD. This damper is a slit damper with very low height to thickness ratio. This device has high shear capacities, and is more economical than SSD devices with high height to thickness ratios. Based on theoretical analysis the formulation for the BSD device's main parameters is derived. Then to investigate the hysteretic behavior of the proposed devices, 5 specimens with different aspect ratios (height-width ratios) were manufactured and tested in a quasi-static manner. The tests revealed that by reducing the aspect ratios, the shear and energy dissipation capacity increases while the displacement...
Numerical study on factors that influence the in-plane drift capacity of unreinforced masonry walls
, Article Earthquake Engineering and Structural Dynamics ; Volume 47, Issue 6 , 2018 , Pages 1440-1459 ; 00988847 (ISSN) ; Nikoukalam, M. T ; Beyer, K ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
Displacement-based assessment procedures require as input reliable estimates of the deformation capacity of all structural elements. For unreinforced masonry (URM) walls, current design codes specify the in-plane deformation capacity as empirical equations of interstory drift. National codes differ with regard to the parameters that are considered in these empirical drift capacity equations, but the inhomogeneity of datasets on URM wall tests renders it difficult to validate the hypotheses with the currently available experimental data. This paper contributes to the future development of such empirical relationships by investigating the sensitivity of the drift capacity to the shear span,...