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Ghehsareh Hadi Roohani Zaghian Ali Zabetzadeh Sayyed Mahmood 《Nonlinear dynamics》2019,96(2):1191-1211
Nonlinear Dynamics - In this paper, a numerical simulation of an anomalous reaction–diffusion process in two-dimensional space with a nonlinear source term is presented. An efficient and... 相似文献
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Hadi Roohani Ghehsareh Ali Zaghian Ahmad Majlesi 《Mathematical Methods in the Applied Sciences》2020,43(6):3637-3649
In the current work, a generalized mathematical model based on the Coimbra time fractional derivative of variable order, which describes an anomalous mobile-immobile transport process in complex systems is investigated numerically. A robust numerical technique based on the meshfree strong form method combined with an efficient time-stepping scheme is performed to compute the approximate solution of the problem with high accuracy. For this purpose, firstly, an effective implicit time discretization approach is used for discretizing the variable-order time fractional problem in the time direction. Then a global meshless technique based on the method of approximate particular solutions is performed to fully discretize the model in the spatial domain. The validity and performance of the procedure to numerically simulate the proposed generalized solute transport model on regular and irregular domains are demonstrated through some numerical examples. 相似文献
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Journal of Thermal Analysis and Calorimetry - Hybrid nanofluids consisting of two or multiple nanoparticles have received much attention in recent decades. In this study, the rheological behavior... 相似文献
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Irvy M. A. Gledhill Hamed Roohani Karl Forsberg Peter Eliasson Beric W. Skews Jan Nordström 《Theoretical and Computational Fluid Dynamics》2016,30(5):449-467
Most computational fluid dynamics simulations are, at present, performed in a body-fixed frame, for aeronautical purposes. With the advent of sharp manoeuvre, which may lead to transient effects originating in the acceleration of the centre of mass, there is a need to have a consistent formulation of the Navier–Stokes equations in an arbitrarily moving frame. These expressions should be in a form that allows terms to be transformed between non-inertial and inertial frames and includes gravity, viscous terms, and linear and angular acceleration. Since no effects of body acceleration appear in the inertial frame Navier–Stokes equations themselves, but only in their boundary conditions, it is useful to investigate acceleration source terms in the non-inertial frame. In this paper, a derivation of the energy equation is provided in addition to the continuity and momentum equations previously published. Relevant dimensionless constants are derived which can be used to obtain an indication of the relative significance of acceleration effects. The necessity for using computational fluid dynamics to capture nonlinear effects remains, and various implementation schemes for accelerating bodies are discussed. This theoretical treatment is intended to provide a foundation for interpretation of aerodynamic effects observed in manoeuvre, particularly for accelerating missiles. 相似文献
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Mehdi Roohani Youssef Habibi Ghanbar Ebrahim Alain Dufresne 《European Polymer Journal》2008,44(8):2489-2498
Nanocomposite materials were prepared from copolymers of polyvinyl alcohol and polyvinyl acetate and a colloidal aqueous suspension of cellulose whiskers prepared from cotton linter. The degree of hydrolysis of the matrix was varied in order to vary the hydrophilic character of the polymer matrix and then the degree of interaction between the filler and the matrix. Nanocomposite films were conditioned at various moisture contents, and the dynamic mechanical and thermal properties were characterized using dynamic mechanical analysis and differential scanning calorimetry, respectively. Tensile tests were performed at room temperature to estimate mechanical properties of the films in the non linear range. All the results show that stronger filler/matrix interactions occur for fully hydrolyzed PVA compared to partially hydrolyzed samples. For moist samples, a water accumulation at the interface was evidenced. The reinforcing effect was found to be all the higher as the degree of hydrolysis of the matrix was high. 相似文献
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Davod Khojasteh Salkuyeh Hadi Roohani Ghehsareh 《Numerical Methods for Partial Differential Equations》2011,27(6):1442-1455
In this article, we first transform the telegraph equation into a system of partial differential equations. Then, we apply the variational iteration method to compute an approximate solution for the telegraph equation. Convergence of the proposed method is also discussed. Finally, some numerical examples are given to show the effectiveness of the proposed method. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 27: 1442–1455, 2011 相似文献
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This paper examines the shock wave dynamics of a biconvex aerofoil in transonic flight during acceleration and retardation.
The aerofoil has a cord length of 1 m and air at infinity is at 101.325 kPa and 300 K. Using Fluent as the CFD software, constant
velocity (steady state) simulations were conducted at transonic Mach numbers. The aerofoil was then accelerated at 1041m/s2 (106 g), starting at Mach 0.1, and decelerated at −1041m/s2, starting at Mach 1.6, through the same range of Mach numbers using time-dependent (unsteady) simulations. Significant differences
were found in the transonic region between the steady and the unsteady aerodynamic forces. Analysis of the flow field in this
region showed that acceleration-dependent variations in the position of the shock wave on the surfaces of the aerofoil were
the main reason for this. As very high accelerations were used in order to emphasize differences, which do not have many practical
applications, simulations using accelerations lower than 9 g were also conducted in order to confirm the results. The acceleration-dependent
behaviour of other shock waves around the aerofoil, such as the bow shock in front of the aerofoil and the trailing wave were
also examined. The trailing wave followed behind the aerofoil changing position with different accelerations at the same Mach
number.
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