Shahr-e Bābak, Iran
Shahr-e Bābak, Iran

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Sayed Razavi M.,Isfahan University of Technology | Shirani E.,Foolad Institute of Technology
Journal of Biomechanics | Year: 2013

In the present study, theoretical formulations for calculation of optimal bifurcation angle and relationship between the diameters of mother and daughter vessels using the power law model for non-Newtonian fluids are developed. The method is based on the distribution of wall shear stress in the mother and daughter vessels. Also, the effect of distribution of wall shear stress on the minimization of energy loss and flow resistance is considered. It is shown that constant wall shear stress in the mother and daughter vessels provides the minimum flow resistance and energy loss of biological flows. Moreover, the effects of different wall shear stresses in the mother and daughter branches, different lengths of daughter branches in the asymmetric bifurcations and non-Newtonian effect of biological fluid flows on the bifurcation angle and the relationship between the diameters of mother and daughter branches are considered. Using numerical simulations for non-Newtonian models such as power law and Carreau models, the effects of optimal bifurcation angle on the pressure drop and flow resistance of blood flow in the symmetric bifurcation are investigated. Numerical simulations show that optimal bifurcation angle decreases the pressure drop and flow resistance especially for bifurcations at large Reynolds number.© 2013.

Monfared M.,Isfahan University of Technology | Shirani E.,Foolad Institute of Technology | Salimpour M.R.,Isfahan University of Technology | Aloui F.,University of Lille Nord de France
Acta Mechanica | Year: 2016

In this research, experimental and numerical techniques are used to study the flow history effects of axial flow on the Couette–Taylor flow. For the experimental investigation, the flow is visualized using the PIV technique with reflective particles with a density of 1.62 g/cm3. Dispersed in a solution, the particles have a strong refraction index equal to 1.85. In this study, two protocols are adopted to study the effect of an axial flow superimposed on a Couette–Taylor flow, and of the history of the flow. The first one, the direct protocol, consists of imposing an azimuthal flow to the inner cylinder. In this case, when the regime is established, the axial flow is superimposed. The second protocol, the inverse protocol, consists of imposing first the axial flow in the gap of the system, after which an azimuthal flow is conveyed. The Couette–Taylor flow with axial flow is strongly dependent on the flow history (the protocol). Thus, the flow structures and development for different protocols are studied and analyzed here experimentally and numerically. In addition, from the numerical results, mathematical models for the two protocols are presented. For the direct protocol, a new relation between the axial Reynolds number, which stabilizes the Couette–Taylor flow, and the Taylor number is presented; for the inverse protocol, a new mathematical model for the critical Taylor number is developed as a function of the axial Reynolds number and also the first critical Taylor number without axial flow. © 2016 Springer-Verlag Wien

Razavi M.S.,Isfahan University of Technology | Shirani E.,Foolad Institute of Technology | Salimpour M.R.,Isfahan University of Technology
AIP Advances | Year: 2014

In the present study, a general method for geometry of fluidic networks is developed with emphasis on pressure-driven flows in the microfluidic applications. The design method is based on general features of network's geometry such as cross-sectional area and length of channels. Also, the method is applicable to various cross-sectional shapes such as circular, rectangular, triangular, and trapezoidal cross sections. Using constructal theory, the flow resistance, energy loss and performance of the network are optimized. Also, by this method, practical design strategies for the fabrication of microfluidic networks can be improved. The design method enables rapid prediction of fluid flow in the complex network of channels and is very useful for improving proper miniaturization and integration of microfluidic networks. Minimization of flow resistance of the network of channels leads to universal constants for consecutive cross-sectional areas and lengths. For a Y-shaped network, the optimal ratios of consecutive cross-section areas (Ai+1/A i) and lengths (Li+1/Li) are obtained as A i+1/Ai = 2-2/3 and Li+1/L i = 2-1/3, respectively. It is shown that energy loss in the network is proportional to the volume of network. It is also seen when the number of channels is increased both the hydraulic resistance and the volume occupied by the network are increased in a similar manner. Furthermore, the method offers that fabrication of multi-depth and multi-width microchannels should be considered as an integral part of designing procedures. Finally, numerical simulations for the fluid flow in the network have been performed and results show very good agreement with analytic results. © 2014 Author(s).

Shumal M.,Isfahan University of Technology | Nili-Ahmadabadi M.,Isfahan University of Technology | Shirani E.,Foolad Institute of Technology
Aerospace Science and Technology | Year: 2016

In the present study, the ball-spine inverse design algorithm is developed for swirling viscous flow regime to improve the performance of an axisymmetric 90-degree bend duct between the radial and axial diffuser of a centrifugal compressor. Performance improvement of the 90-degree bend duct is accomplished to increase its pressure recovery without separation. First, the effects of geometric parameters on flow separation are numerically studied and a safe margin is obtained for prevention of flow separation and stall. Then, the safe margin is enlarged to reach a higher pressure recovery via the shape modification of duct walls. The shape modification process integrates the BSA as shape modification algorithm and an axisymmetric flow analysis code as flow solver. Shape modification process is carried out by improving the current wall pressure distribution and applying it to the inverse design algorithm. Results show merits and robustness of the BSA for duct design in swirling viscous flow regime whereby the pressure recovery coefficient of the 90-degree bend duct increases up to 7%. © 2016 Elsevier Masson SAS. All rights reserved.

Rahmati A.R.,University of Kashan | Ashrafizaadeh M.,Isfahan University of Technology | Shirani E.,Foolad Institute of Technology
Journal of Applied Fluid Mechanics | Year: 2014

In the present work, for the first time, the application of a Multi-Relaxation-Time Lattice Boltzmann (MRT-LB) model for large-eddy simulation (LES) of turbulent thermally driven flows on non-uniform grids is considered. A Taylor series expansion and Least square based Lattice Boltzamnn method (TLLBM) has been implemented in order to use a nonuniform mesh. It permits to reduce the required mesh size and consequently the computational cost to simulate the turbulent buoyant flow fields. The implementation is discussed in the context of a MRT-LB model in conjunction with both Smagorinsky and mixed scale viscosity sub-grid models. At first, to validate the code, a multi-relaxation-time lattice Boltmann method on non-uniform grid is utilized to simulate a lid-driven cavity flow .Then large eddy simulation of this model is applied to simulate a turbulent Rayleigh-Bénard convection at different Rayleigh numbers in ranging 104 to 1015 for Prantdl number of 0.71. The simulation results show that lattice Boltzmann method is capable to simulate turbulent convection flow problems at high Rayleigh numbers.

Zare M.,Isfahan University of Technology | Daneshi M.,Isfahan University of Technology | Shirani E.,Foolad Institute of Technology | Salimpour M.R.,Isfahan University of Technology
International Journal of Heat and Mass Transfer | Year: 2014

Effects of blood vessels in a living tissue subjected to heat transfer radiation are investigated. The heat transfer between blood flowing inside vessels and the tissue around the vessels is considered. For this purpose, temperature distributions in three-dimensional space are evaluated by solving the continuity, momentum and energy equations, numerically. Blood is considered as non-Newtonian fluid using the power law model. A precise and realistic model for skin and blood vessels is used to analyze the transient heat transfer through skin. Skin is considered as a three-dimensional structure including three layers embedded with counter-current vessels, with optimally branched circular cross sectional areas. Results for temperature distribution show that arteries act as heat sinks while veins carry heat out of the upper part of the tissue. It is observed that the role of blood for cooling the tissue under radiation is more significant than what was assumed in previous studies. Also, skin burn degree induced by radiation is evaluated. It was seen that skin burn is a function of time and temperature. Arteries restrict the skin burn-depth while the veins act oppositely. © 2014 Elsevier Ltd. All rights reserved.

Shumal M.,Isfahan University of Technology | Nili-Ahmadabadi M.,Isfahan University of Technology | Shirani E.,Foolad Institute of Technology
Proceedings of the ASME Turbo Expo | Year: 2016

In the present study, the performance of a centrifugal compressor is improved by replacing the combination of vaned radial diffuser and axisymmetric vaneless 90-degree bend by a vaned 90-degree bent diffuser. It controls the outlet flow angle and reduces the overall diameter of the compressor. The optimum number of guide vanes inside the 90-degree bent diffuser is obtained using 3-D numerical simulation. Indeed, changing flow direction simultaneous with decreasing flow velocity through the 90-degree bent diffuser will increase the possibility of secondary flow and separation. Here, the meridional plane of the 90-degree bent diffuser is modified to reduce secondary flow and separation. Geometry modification process integrates Ball-Spine inverse design method as the shape modification algorithm and a quasi- 3D analysis code as the flow solver. The current quasi-3D flow solver is in fact a 3-D flow solver that solves viscous flow between two virtual guide vanes located at a very close distance with free slip condition over them. In other words, in the current quasi-3D analysis, stream surfaces are the same as the virtual guide vanes and no slip condition is just applied on the hub and shroud. Shape modification process is carried out by improving the current hub and shroud pressure distribution and applying it to the inverse design algorithm. Spines directions are specified in a way that geometry would change only in the meriodional plane and guide vanes angle remain unchanged in the blade to blade plane through the geometry modification process. Having modified the meridional plane, the new vaned 90-degree bent diffuser is examined by the 3-D flow solver. Results show not only the secondary flow is reduced in the new 90-degree bent diffuser, but also its efficiency increases up to 2%. On the other hand, the overall diameter of the compressor decreases about 24%. Copyright © 2016 by ASME

Alavi S.,Foolad Institute of Technology
International Journal of Technological Learning, Innovation and Development | Year: 2016

A lack of workforce agility has been reported as one of the main reasons that some enterprises have difficulty keeping pace with markets and technological changes. Shortage of research on the consequences of workforce agility can be one of the main reasons for inconsideration about workforce agility in SMEs. In order to contribute to this debate, this research investigates whether and how extent workforce agility is a critical factor for promoting external manufacturing flexibility, as a key component in dynamic environment. The study is conducted by gathering sample from 161 Iranian SMEs. Supporting the hypotheses, the results suggest workforce agility enhances new product, mix, and volume flexibility. Moreover, testing the relationship between external manufacturing flexibility dimensions shows that mix flexibility encourages volume and new product flexibility in the SMEs. © Copyright 2016 Inderscience Enterprises Ltd.

Dadkhah M.,Foolad Institute of Technology | Davarpanah Jazi M.,Foolad Institute of Technology
Advances in Environmental Biology | Year: 2014

Phishing is an attack related to social engineering which uses some websites for achieving its pre-determined goals. Phishing attacks include stealing passwords and credit cards profiles of users who make internet purchases. Such attacks are increasing and are among the main techniques of internet fraudsters. In spite of the growth of phishing attacks, no comprehensive solution has been presented to fight them up to now.Different techniques are used for protecting users against phishing attacks. Some of these are implemented in client respect and some are applied to server and each has its own strategy. In the present paper we review phishing attacks thoroughly, which includes the process of a phishing attack and classification of such attacks. Then, we investigate phishing fighting techniques and review their advantages and disadvantages. Finally, we provide a framework for fighting such attack. The presented framework is not dependent on a particular software or hardware and is efficient for fighting different types of phishing attacks. © 2014 AENSI Publisher All rights reserved.

Karimipour A.,Islamic Azad University at Najafabad | Hossein Nezhad A.,University of Sistan and Baluchestan | D'Orazio A.,University of Rome La Sapienza | Hemmat Esfe M.,Islamic Azad University at Najafabad | And 2 more authors.
European Journal of Mechanics, B/Fluids | Year: 2015

Laminar forced convection heat transfer of water-Cu nanofluids in a microchannel was studied utilizing the lattice Boltzmann method (LBM). The entering flow was at a lower temperature compared to the microchannel walls. Simulations were performed for nanoparticle volume fractions of 0.00 to 0.04 and slip coefficient from 0.005 to 0.02. The model predictions were found to be in good agreement with earlier studies. The effects of wall slip velocity and temperature jump of the nanofluid were studied for the first time by using lattice Boltzmann method. Streamlines, isotherms, longitudinal variations of Nusselt number, slip velocity and temperature jump as well as velocity and temperature profiles for different cross sections were presented. The results indicate that LBM can be used to simulate forced convection for the nanofluid micro flows. Moreover, the effect of the temperature jump on the heat transfer rate is significant. Also, the results showed that decreasing the values of slip coefficient enhances the convective heat transfer coefficient and consequently the Nusselt number (Nu) but increases the wall slip velocity and temperature jump values. © 2014 Elsevier Masson SAS. All rights reserved.

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