Search for: aspect-ratio
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    Analytical solutions for the size dependent buckling and postbuckling behavior of functionally graded micro-plates

    , Article International Journal of Engineering Science ; Volume 100 , 2016 , Pages 45-60 ; 00207225 (ISSN) Taati, E ; Sharif University of Technology
    Elsevier Ltd  2016
    In this study, the buckling and postbuckling analysis of FG micro-plates under different kinds of traction on the edges is investigated based on the modified couple stress theory. The static equilibrium equations of an FG rectangular micro-plate as well as the boundary conditions are derived using the principle of minimum total potential energy. The analytical solutions are developed for three case studies including: simply supported micro-plates subjected to uniform transverse load and biaxial tractions, clamped-simply supported micro-plates under uniform transverse load and axial traction, and simply supported micro-plates subjected to shear traction. All plate properties except the length... 

    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) Taati, E ; Sina, N ; Sharif University of Technology
    Springer Verlag  2018
    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... 

    Parametric study of buckling and post-buckling behavior for an aluminum hull structure of a high-aspect-ratio twin hull vessel

    , Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; Volume 234, Issue 1 , 2020 , Pages 15-25 Soleimani, E ; Tabeshpour, M. R ; Seif, M. S ; Sharif University of Technology
    SAGE Publications Ltd  2020
    Metal plates are essential parts of structures such as ship hulls and offshore oil platforms. These plates are typically under compressive axial forces. Hence, one of the main mechanisms for failure and collapse of such structures is buckling of plates. Thus, for safe and secure design, buckling strength of plates should be evaluated. Finite element analysis techniques are perfect tools for this purpose because of the accuracy and flexibility for performing simulations with different variables. In this study, the strength of aluminum plates has been studied using finite element analysis software and it was tried to study the influence of variables such as initial imperfections, plate... 

    An analysis of carbone monoxide distribution in large tunnel fires

    , Article Journal of Mechanical Science and Technology ; Vol. 28, Issue. 5 , 2014 , pp. 1917-1925 ; ISSN: 1738494X Sojoudi, A ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
    Fire events and the related toxicants such as CO are responsible for many fatalities in the current century. These hazardous events are much more dangerous when they occur in enclosed spaces. In the present study, a theoretical relation is developed for horizontal distribution of CO in a large tunnel fire. Then, the developed criterion is used to study the effect of some rudimentary parameters such as the heat release rate (HRR) of fire and tunnel's aspect ratio (AR) on CO and temperature stratification. Theoretical results of various heat release rates and aspect ratios for horizontal distribution of CO are compared with numerical results using fire dynamics simulator (FDS5.5). It is found... 

    On the mechanical characteristics of graphene nanosheets: A fully nonlinear modified Morse model

    , Article Nanotechnology ; Volume 31, Issue 11 , 2020 Shoghmand Nazarloo, A ; Ahmadian, M ; Firoozbakhsh, K ; Sharif University of Technology
    Institute of Physics Publishing  2020
    In this paper, the mechanical properties of graphene nanosheets are evaluated based on the nonlinear modified Morse model. The interatomic interactions including stretching and bending of the covalent bonds between carbon atoms, are replaced by nonlinear extensional and torsional spring-like elements. The finite element method is implemented to analyze the model under different loading conditions and linear characteristics of the graphene structure including the Young's modulus, surface modulus, shear modulus and Poisson's ratio are evaluated for various geometries and chirality where these properties are shown to be size and aspect ratio dependent. It is also found that when the dimensions... 

    An efficient method for nonlinear aeroelasticy of slender wings

    , Article Nonlinear Dynamics ; Volume 67, Issue 1 , 2012 , Pages 659-681 ; 0924090X (ISSN) Shams, S ; Sadr, M. H ; Haddadpour, H ; Sharif University of Technology
    This paper aims the nonlinear aeroelastic analysis of slender wings using a nonlinear structural model coupled with the linear unsteady aerodynamic model. High aspect ratio and flexibility are the specific characteristic of this type of wings. Wing flexibility, coupled with long wingspan can lead to large deflections during normal flight operation of an aircraft; therefore, a wing in vertical/forward-afterward/torsional motion using a third-order form of nonlinear general flexible Euler-Bernoulli beam equations is used for structural modeling. Unsteady linear aerodynamic strip theory based on the Wagner function is used for determination of aerodynamic loading on the wing. Combining these... 

    Three-dimensional numerical simulation of a novel electroosmotic micromixer

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 119 , 2017 , Pages 25-33 ; 02552701 (ISSN) Shamloo, A ; Madadelahi, M ; Abdorahimzadeh, S ; Sharif University of Technology
    Elsevier B.V  2017
    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... 

    Inertial particle focusing in serpentine channels on a centrifugal platform

    , Article Physics of Fluids ; Volume 30, Issue 1 , 2018 ; 10706631 (ISSN) Shamloo, A ; Mashhadian, A ; Sharif University of Technology
    American Institute of Physics Inc  2018
    Inertial particle focusing as a powerful passive method is widely used in diagnostic test devices. It is common to use a curved channel in this approach to achieve particle focusing through balancing of the secondary flow drag force and the inertial lift force. Here, we present a focusing device on a disk based on the interaction of secondary flow drag force, inertial lift force, and centrifugal forces to focus particles. By choosing a channel whose cross section has a low aspect ratio, the mixing effect of the secondary flow becomes negligible. To calculate inertial lift force, which is exerted on the particle from the fluid, the interaction between the fluid and particle is investigated... 

    Exploring contraction–expansion inertial microfluidic-based particle separation devices integrated with curved channels

    , Article AIChE Journal ; Volume 65, Issue 11 , 2019 ; 00011541 (ISSN) Shamloo, A ; Abdorahimzadeh, S ; Nasiri, R ; Sharif University of Technology
    John Wiley and Sons Inc  2019
    Separation of particles or cells has various applications in biotechnology, pharmaceutical and chemical industry. Inertial cell separation, in particular, has been gaining a great attention in the recent years since it has exhibited a label-free, high-throughput and efficient performance. In this work, first, an inertial contraction–expansion array microchannel device, capable of passively separating two particles with diameters of 4 and 10 μm, was numerically studied. Then, the validated model was combined with curved geometries in order to investigate the effect of curve features on the separation process. The overall purpose was to investigate the interaction between the two different... 

    A practical method for aerodynamic investigation of WIG

    , Article Aircraft Engineering and Aerospace Technology ; Volume 88, Issue 1 , 2016 , Pages 73-81 ; 00022667 (ISSN) Seif, M. S ; Tavakoli Dakhrabadi, M ; Sharif University of Technology
    Emerald Group Publishing Ltd  2016
    Purpose - The purpose of this paper is to present a fast, economical and practical method for mathematical modeling of aerodynamic characteristics of rectangular wing in ground (WIG) effect. Design/methodology/approach - Reynolds averaged Navier-Stokes (RANS) equations were converted to Bernoulli equation by reasonable assumptions. Also, Helmbold's equation has been developed for calculation of the slope of wing lift coefficient in ground effect by defining equivalent aspect ratio (ARe). Comparison of present work results against the experimental results has shown good agreement. Findings - A practical mathematical modeling with lower computational time and higher accuracy was presented for... 

    Frequency-dependent energy harvesting via magnetic shape memory alloys

    , Article Smart Materials and Structures ; Volume 24, Issue 11 , October , 2015 ; 09641726 (ISSN) Sayyaadi, H ; Askari Farsangi, M. A ; Sharif University of Technology
    Institute of Physics Publishing  2015
    This paper is focused on presenting an accurate framework to describe frequency-dependent energy harvesting via magnetic shape memory alloys (MSMAs). Modeling strategy incorporates the phenomenological constitutive model developed formerly together with the magnetic diffusion equation. A hyperbolic hardening function is employed to define reorientation-induced strain hardening in the material, and the diffusion equation is used to add dynamic effects to the model. The MSMA prismatic specimen is surrounded by a pickup coil, and the induced voltage during martensite-variant reorientation is investigated with the help of Faraday's law of magnetic field induction. It has been shown that, in... 

    The effect of nanopores geometry on desalination of single-layer graphene-based membranes: A molecular dynamics study

    , Article Journal of Molecular Liquids ; Volume 339 , 2021 ; 01677322 (ISSN) Sarvestani, A. B ; Chogani, A ; Shariat, M ; Moosavi, A ; Kariminasab, H ; Sharif University of Technology
    Elsevier B.V  2021
    The water desalination process using nanoporous single-layer graphene membranes is simulated through classical molecular dynamics. The effect of nanopores shapes on the capacity of the membrane for filtration of water is investigated. According to the results, the geometry of the nanopores considerably affects the performance of the membrane and can completely change the water flow rate and salt rejection. The results reveal that the effective area of the nanopores plays a critical role and for a better understanding of the impact of this parameter, aspect ratio and the equal diameter of noncircular pores based on different methods such as equal area, equal perimeter, and hydraulic diameter... 

    Seismic evaluation of steel plate shear wall systems considering soil-structure interaction

    , Article Soil Dynamics and Earthquake Engineering ; Volume 145 , 2021 ; 02677261 (ISSN) Sarcheshmehpour, M ; Shabanlou, M ; Meghdadi, Z ; Estekanchi, H. E ; Mofid, M ; Sharif University of Technology
    Elsevier Ltd  2021
    This study investigates the various effects of Soil-Structure Interaction (SSI) on the seismic behavior of steel frames with Steel Plate Shear Wall (SPSW) lateral resisting systems. Nine steel frames with various aspect ratios are studied under multiple seismic hazard levels. The SPSWs are modeled based on the strip model concept, and the Soil-Structure Systems are simulated using the substructure method. The soil beneath the structure is considered as a homogeneous elastic half-space. The Endurance Time method is exploited for nonlinear dynamic analysis of the fixed-base structures and soil-structure systems. Results indicate that use of fixed-base models leads to the significant... 

    Surfactant-assisted synthesis and characterization of hydroxyapatite nanorods under hydrothermal conditions

    , Article Materials Science- Poland ; Volume 27, Issue 4 , 2009 , Pages 961-971 ; 01371339 (ISSN) Salarian, M ; Solati Hashjin, M ; Sara Shafiei, S ; Goudarzi, A ; Salarian, R ; Nemati, A ; Sharif University of Technology
    Hydroxyapatite (HAp) nanorods with uniform morphology and controllable size were successfully synthesized by precipitating Ca(NO3) 24H2O and (NH4)2HPO4 in the presence of cetyltrimethylammonium bromide (CTAB) and polyethylene glycol 400 (PEG 400) as cationic surfactant and non-ionic cosurfactant, respectively, under hydrothermal conditions. The effect of hydrothermal temperature on the composition, morphology and size of HAp particles was studied using X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR) and scanning electron microscopy (SEM). Results revealed that the morphology and size of HAp particles can be effectively controlled by the presence of CTAB and PEG... 

    Template-directed hydrothermal synthesis of dandelion-like hydroxyapatite in the presence of cetyltrimethylammonium bromide and polyethylene glycol

    , Article Ceramics International ; Volume 35, Issue 7 , 2009 , Pages 2563-2569 ; 02728842 (ISSN) Salarian, M ; Solati Hashjin, M ; Shafiei, S. S ; Salarian, R ; Nemati, Z. A ; Sharif University of Technology
    A template-directed synthetic method, using surfactant cetyltrimethylammonium bromide (CTAB) as a template and co-surfactant polyethylene glycol (PEG600) as a co-template under hydrothermal conditions, has been applied to obtain dandelion-like HAp. The morphology, size, crystalline phase, chemical composition, physical characteristics, and thermal behavior of the product were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier ransform infrared spectroscopy (FTIR), induced coupled plasma spectroscopy (ICP), BET (Brunauer, Emmett, and Teller) method, and simultaneous thermal analysis (STA). SEM and TEM... 

    Potential application of single-layered graphene sheet as strain sensor

    , Article Solid State Communications ; Volume 147, Issue 7-8 , August , 2008 , Pages 336-340 ; 00381098 (ISSN) Sakhaee Pour, A ; Ahmadian, M. T ; Vafai, A ; Sharif University of Technology
    Molecular structural mechanics is implemented to investigate the vibrational characteristics of defect-free single-layered graphene sheets (SLGSs), which have potential applications as strain sensors. The effect of strain on the fundamental frequencies of the defect-free zigzag and armchair models with clamped-clamped boundary condition is studied. The atomistic modeling results reveal while sensitivities of the strain sensors are not influenced significantly by chirality, they can be slightly increased by decreasing aspect ratios of the sheets. It is further shown that the SLGSs-based strain sensors are more sensitive to the applied stretch than the SWCNTs versions. © 2008 Elsevier Ltd. All... 

    Applications of single-layered graphene sheets as mass sensors and atomistic dust detectors

    , Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 11 , 2007 , Pages 99-104 ; 079184305X (ISBN) Sakhaee-Pour, A ; Ahmadian, M. T ; Vafai, A ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2007
    Molecular structural mechanics is implemented to model vibrational behavior of defect free single-layered graphene sheets (SLGSs) at constant temperature. To mimic these two-dimensional layers, zigzag and armchair models with cantilever and bridge boundary conditions are adopted. Fundamental frequencies of these nano structures are calculated, and it is perceived that they are independent of the chirality and aspect ratio. Effects of point mass and atomistic dust on the fundamental frequencies are also considered in order to investigate the possibility of using SLGSs as sensors. Results of exhibit the principle frequencies are highly sensitive to the added mass in the order of 10-6 fg.... 

    Numerical investigation of the swirling air diffuser: Parametric study and optimization

    , Article Energy and Buildings ; Volume 43, Issue 6 , June , 2011 , Pages 1329-1333 ; 03787788 (ISSN) Sajadi, B ; Saidi, M. H ; Mohebbian, A ; Sharif University of Technology
    During the recent decade, high induction diffusers have become more appealing in applications which require relatively high ventilation airflow rates, such as clean rooms. In this research, the effect of geometric parameters on the performance of a specific type of swirling air diffuser is investigated numerically. The results show that although the diffuser slots geometry, namely their angle and aspect ratio, is impressive on the diffuser performance, it is not as important as the swirling blade angle and the performance is almost constant in a wide range of slots specifications. The results also demonstrate that the diffuser performance and the resultant indoor airflow distribution highly... 

    Forced convective heat transfer in parallel flow multilayer microchannels

    , Article Journal of Heat Transfer ; Volume 129, Issue 9 , 2007 , Pages 1230-1236 ; 00221481 (ISSN) Saidi, M. H ; Hajiaghaee Khiabani , R ; Sharif University of Technology
    In this paper, the effect of increasing the number of layers on improving the thermal performance of microchannel heat sinks is studied. In this way, both numerical and analytical methods are utilized. The analytical method is based on the porous medium assumption. Here, the modified Darcy equation and the energy balance equations are used. The method has led to an analytical expression presenting the average dimensionless temperature field in the multilayer microchannel heat sink. The effects of different parameters such as aspect ratio, porosity, channel width, and the solid properties on the thermal resistance are described. The results for single layer and multilayer heat sinks are... 

    Coanda surface geometry optimization for multi-directional co-flow fluidic thrust vectoring

    , Article Proceedings of the ASME Turbo Expo: Power for Land, Sea, and Air ; Volume 5 , 2009 , Pages 183-189 ; 9780791848869 (ISBN) Saghafi, F ; Banazadeh, A ; Sharif University of Technology
    The performance of Co-flow fluidic thrust vectoring is a function of secondary flow characteristics and the fluidic nozzle geometry. In terms of nozzle geometry, wall shape and the secondary slot aspect ratio are the main parameters that control the vector angle. The present study aims to find a high quality wall shape to achieve the best thrust vectoring performance, which is characterized by the maximum thrust deflection angle with respect to the injected secondary air. A 3D computational fluid dynamics (CFD) model is employed to investigate the flow characteristics in thrust vectoring system. This model is validated using experimental data collected from the deflection of exhaust gases of...