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Mohammadi R.,Islamic Azad University at Neyshabur
Chinese Physics B | Year: 2015

The aim of the present paper is to present a numerical algorithm for the time-dependent generalized regularized long wave equation with boundary conditions. We semi-discretize the continuous problem by means of the Crank-Nicolson finite difference method in the temporal direction and exponential B-spline collocation method in the spatial direction. The method is shown to be unconditionally stable. It is shown that the method is convergent with an order of O(k2 + h2). Our scheme leads to a tri-diagonal nonlinear system. This new method has lower computational cost in comparison to the Sinc-collocation method. Finally, numerical examples demonstrate the stability and accuracy of this method. © 2015 Chinese Physical Society and IOP Publishing Ltd. Source


Moshizi S.A.,Islamic Azad University at Neyshabur
Engineering Computations (Swansea, Wales) | Year: 2015

Purpose - The purpose of this paper is to focus on convective heat and mass transfer characteristics of Cu-water nanofluid inside a porous microchannel in the presence of a uniform magnetic field. The walls of the microchannel are subjected to constant asymmetric heat fluxes and also the first order catalytic reaction. To represent the non-equilibrium region near the surfaces, the Navier's slip condition is considered at the surfaces because of the non-Adherence of the fluid-solid interface and the microscopic roughness in microchannels. Design/methodology/approach - Employing the Brinkman model for the flow in the porous medium and the "clear fluid compatible" model as a viscous dissipation model, the conservative partial differential equations have been transformed into a system of ordinary ones via the similarity variables. Closed form exact solutions are obtained analytically based on dimensionless parameters of velocity, temperature and species concentration. Findings - Results show that the addition of Cu-nanoparticles to the fluid has a significant influence on decreasing concentration, temperature distribution at the both walls and velocity profile along the microchannel. In addition, total heat transfer in microchannel increases as nanoparticles add to the fluid. Slip parameter and Hartmann number have the decreasing effects on concentration and temperature distributions. Slip parameter leads to increase velocity profiles, while Hartmann number has an opposite trend in velocity profiles. These two parameters increase the total heat transfer rate significantly. Originality/value - In the present study, a comprehensive analytical solution has been obtained for convective heat and mass transfer characteristics of Cu-water nanofluid inside a porous microchannel in the presence of a uniform magnetic field. Finally, the effects of several parameters such as Darcy number, nanoparticle volume fraction, slip parameter, Hartmann number, Brinkman number, asymmetric heat flux parameter, Soret and Damkohler numbers on total heat transfer rate and fluid flow profiles are studied in more detail. To the best of author's knowledge, no study has been conducted to this subject and the results are original. © Emerald Group Publishing Limited. Source


Sadatian S.D.,Islamic Azad University at Neyshabur
International Journal of Modern Physics D | Year: 2012

We have studied a DGP-inspired braneworld scenario where the idea of Lorentz invariance violation has been combined into a specifying preferred frame that embed a dynamical normal vector field to brane. We propose the Lorentz violating DGP brane models with enough parameters can explain crossing of phantom divide line. Also we have considered the model for proper cosmological evolution that is according to the observed behavior of the equation of state. In other view point, we have described a Rip singularity solution of model that occur in this model. © 2012 World Scientific Publishing Company. Source


Malvandi A.,Amirkabir University of Technology | Hedayati F.,Islamic Azad University at Neyshabur | Ganji D.D.,Babol Noshirvani University of Technology
Powder Technology | Year: 2014

Unsteady two-dimensional stagnation point flow of a nanofluid over a stretching sheet is investigated numerically. In contrast to the conventional no-slip condition at the surface, Navier's slip condition has been applied. The behavior of the nanofluid was investigated for three different nanoparticles in the water-base fluid, namely copper, alumina and titania. Employing the similarity variables, the governing partial differential equations including continuity, momentum and energy have been reduced to ordinary ones and solved via Runge-Kutta-Fehlberg scheme. It was shown that a dual solution exists for negative values of the unsteadiness parameter A and, as it increases, the skin friction Cfr grows but the heat transfer rate Nur takes a decreasing trend. The results also indicated that, unlike the stretching parameter ε, increasing in the values of the slip parameter λ widen the ranges of the unsteadiness parameter A for which the solution exists. Furthermore, it was found that an increase in both ε and λ intensifies the heat transfer rate. © 2013 Elsevier B.V. Source


Ramezanpour A.,Islamic Azad University at Neyshabur
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2016

We study the inverse problem of constructing an appropriate Hamiltonian from a physically reasonable set of orthogonal wave functions for a quantum spin system. Usually, we are given a local Hamiltonian and our goal is to characterize the relevant wave functions and energies (the spectrum) of the system. Here, we take the opposite approach; starting from a reasonable collection of orthogonal wave functions, we try to characterize the associated parent Hamiltonians, to see how the wave functions and the energy values affect the structure of the parent Hamiltonian. Specifically, we obtain (quasi) local Hamiltonians by a complete set of (multilayer) product states and a local mapping of the energy values to the wave functions. On the other hand, a complete set of tree wave functions (having a tree structure) results to nonlocal Hamiltonians and operators which flip simultaneously all the spins in a single branch of the tree graph. We observe that even for a given set of basis states, the energy spectrum can significantly change the nature of interactions in the Hamiltonian. These effects can be exploited in a quantum engineering problem optimizing an objective functional of the Hamiltonian. © 2016 American Physical Society. Source

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