Filters








11 Hits in 1.0 sec

Melting of a phase change material in a horizontal annulus with discrete heat sources

Hooshyar Mirzaei, Abdolrahman Dadvand, Mohammad Mastiani, Seyed Sebti, Sina Kashani
2015 Thermal Science  
Phase change materials have found many industrial applications such as cooling of electronic devices and thermal energy storage. This paper investigates numerically the melting process of a phase change material in a 2-D horizontal annulus with different arrangements of two discrete heat sources. The sources are positioned on the inner cylinder of the annulus and assumed as constant-temperature boundary conditions. The remaining portion of the inner cylinder wall as well as the outer cylinder
more » ... ll is considered to be insulated. The emphasis is mainly on the effects of the arrangement of the heat source pair on the fluid flow and heat transfer features. The governing equations are solved on a non-uniform O type mesh using a pressure-based finite volume method with an enthalpy porosity technique to trace the solid and liquid interface. The results are obtained at Ra = 10 4 and presented in terms of streamlines, isotherms, melting phase front, liquid fraction, and dimensionless heat flux. It is observed that, depending on the arrangement of heat sources, the liquid fraction increases both linearly and non-linearly with time but will slow down at the end of the melting process. It can also be concluded that proper arrangement of discrete heat sources has the great potential in improving the energy storage system. For instance, the arrangement C.3 where the heat sources are located on the bottom part of the inner cylinder wall can expedite the melting process as compared to the other arrangements.
doi:10.2298/tsci121024094m fatcat:flc5lgkjrvdunmqvavz2w7572u

Solution of the fractional diffusion equation with the Riesz fractional derivative using McCormack method

Ahmad Reza Haghighi, Abdolrahman Dadvand, Hamideh Hoseini Ghejlo
2014 Communications on Advanced Computational Science with Applications  
This paper aims to approximate the fractional diffusion equations with the Riesz fractional derivative in a finite domain utilizing the McCormack numerical method with a second order accuracy. To approximate the Riesz fractional derivative, the fractional central difference is used. The fractional derivative error is obtained for the central fractional difference and the stability of the McCormack numerical method is studied. Some numerical examples are given to evidence the maximum error
more » ... ed when the McCormack method is utilized for the solution of the fractional diffusion equations using the fractional central difference.
doi:10.5899/2014/cacsa-00024 fatcat:npknu5uaajguxafxz75akv5s64

A systematic study for determining the optimal relaxation time in the lattice Boltzmann method at low Reynolds numbers

Mansoor Jadidi, Michael J. Simmonds, Abdolrahman Dadvand, Geoff Tansley
2021 Alexandria Engineering Journal  
In the lattice Boltzmann method (LBM), the relaxation time plays a significant role in the accuracy of simulation. However, there has been little attention directed toward evaluating the optimal relaxation time in literature. This paper proposes a systematic approach for the determination of the optimal relaxation time, particularly for very-low Reynolds (Re) number flows as analogues for blood flow in micro-vessels. The LBM with D2Q9 lattice model is used to simulate Poiseuille flow in a
more » ... channel and its accuracy is verified against the analytical solution. It was found that for a given number of grid points in the y-direction, the value of optimal relaxation time predicted analytically differs from that obtained from the numerical solutions. This indicates that the analytical relaxation time should be corrected when used in the LBM code. Ó 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
doi:10.1016/j.aej.2021.06.037 fatcat:ybpjrp2g4jaunpwnkmaipo7hey

Aerodynamic shape optimization and analysis of small wind turbine blades employing the Viterna approach for post-stall region

Arash Hassanzadeh, Armin Hassanzadeh Hassanabad, Abdolrahman Dadvand
2016 Alexandria Engineering Journal  
This paper aims to optimize the distribution of chord and twist angle of small wind turbine blade in order to maximize its Annual Energy Production (AEP). A horizontal-axis wind turbine (HAWT) blade is optimized using a calculation code based on the Blade Element Momentum (BEM) theory. A difficult task in the implementation of the BEM theory is the correct representation of the lift and drag coefficients at post-stall regime. In this research, the method based on the Viterna equations was used
more » ... or extrapolating airfoil data into the post-stall regime and the results were compared with various mathematical models. Results showed the high capability of this method to predict the performance of wind turbines. Evaluation of the efficiency of wind turbine blade designed with the proposed model shows that the optimum design parameters gave rise to an increase of 8.51% in the AEP rate as compared with the corresponding manufactured operating parameters. Ó 2016 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
doi:10.1016/j.aej.2016.07.008 fatcat:pscajgenzbga3bvw7odbkqykzi

Study of the Effect of Gas Channels Geometry on the Performance of Polymer Electrolyte Membrane Fuel Cell

Nima Ahmadi, Sajad Rezazadeh, Abdolrahman Dadvand, Iraj Mirzaee
2017 Periodica Polytechnica: Chemical Engineering  
This study focuses on the effect of gas channels geometry on the performance of polymer electrolyte membrane fuel cell. A set of empirical tests are accomplished to study these effects. The cross section of the gas channel is changed from square to inverse trapezoid, that is, the bottom width of the channel is kept fixed at 1mm while the width of the top of the channel is increased with the discontinuity of 0.2mm from 1mm to 1.6mm. Results show that the best performance is obtained for the
more » ... se trapezoid channel with the 1.2mm width in the top section of channel. Moreover to verify the experimental test results, a 3-D finite volume method in-house code is brought up to solve the conservation equations. Hereafter, the nozzle shape gas channel efficacy is investigated experimentally and the obtained results are verified by numerical results. The obtained results determine that, at an equable voltage, this new configuration of the channels enhances the current density output by cells as compared to the primary model (i.e., gas channel with square cross section area). This finding may be due to the increase of reactant velocity in the channel.
doi:10.3311/ppch.9369 fatcat:te3fvv7fwzcqpadlulwxhi5enq

Simulation of Fluid-Structure and Fluid-Mediated Structure-Structure Interactions in Stokes Regime Using Immersed Boundary Method

Masoud Baghalnezhad, Abdolrahman Dadvand, Iraj Mirzaee
2014 The Scientific World Journal  
The Stokes flow induced by the motion of an elastic massless filament immersed in a two-dimensional fluid is studied. Initially, the filament is deviated from its equilibrium state and the fluid is at rest. The filament will induce fluid motion while returning to its equilibrium state. Two different test cases are examined. In both cases, the motion of a fixed-end massless filament induces the fluid motion inside a square domain. However, in the second test case, a deformable circular string is
more » ... placed in the square domain and its interaction with the Stokes flow induced by the filament motion is studied. The interaction between the fluid and deformable body/bodies can become very complicated from the computational point of view. An immersed boundary method is used in the present study. In order to substantiate the accuracy of the numerical method employed, the simulated results associated with the Stokes flow induced by the motion of an extending star string are compared well with those obtained by the immersed interface method. The results show the ability and accuracy of the IBM method in solving the complicated fluid-structure and fluid-mediated structure-structure interaction problems happening in a wide variety of engineering and biological systems.
doi:10.1155/2014/782534 pmid:24711736 pmcid:PMC3953420 fatcat:iixsfwlunjc6fducg3z6jp4yje

Numerical study of the melting of nano-enhanced phase change material in a square cavity

Seyed Sahand Sebti, Mohammad Mastiani, Hooshyar Mirzaei, Abdolrahman Dadvand, Sina Kashani, Seyed Amir Hosseini
2013 Journal of Zhejiang University: Science A  
A comprehensive numerical study was conducted to investigate heat transfer enhancement during the melting process in a 2D square cavity through dispersion of nanoparticles. A paraffin-based nanofluid containing various volume fractions of Cu was applied. The governing equations were solved on a non-uniform mesh using a pressure-based finite volume method with an enthalpy porosity technique to trace the solid-liquid interface. The effects of nanoparticle dispersion in a pure fluid and of some
more » ... nificant parameters, namely nanoparticle volume fraction, cavity size and hot wall temperature, on the fluid flow, heat transfer features and melting time were studied. The results are presented in terms of temperature and velocity profiles, streamlines, isotherms, moving interface position, solid fraction and dimensionless heat flux. The suspended nanoparticles caused an increase in thermal conductivity of nano-enhanced phase change material (NEPCM) compared to conventional PCM, resulting in heat transfer enhancement and a higher melting rate. In addition, the nanofluid heat transfer rate increased and the melting time decreased as the volume fraction of nanoparticles increased. The higher temperature difference between the melting temperature and the hot wall temperature expedited the melting process of NEPCM.
doi:10.1631/jzus.a1200208 fatcat:i4c2m7giw5gj3ehi22hwzyys34

Analysis of the operating pressure and GDL geometrical configuration effect on PEM fuel cell performance

Nima Ahmadi, Abdolrahman Dadvand, Sajad Rezazadeh, Iraj Mirzaee
2016 Journal of the Brazilian Society of Mechanical Sciences and Engineering  
doi:10.1007/s40430-016-0548-0 fatcat:u5acov36svbyhlnurgnwwp3vnm

A unified finite volume framework for phase‐field simulations of an arbitrary number of fluid phases

Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Abdolrahman Dadvand, Martin Wörner, Holger Marschall
2022
Abdolrahman Dadvand: Conceptualization; formal analysis; investigation; methodology; writingreview and editing.  ...  Roisman https://orcid.org/0000-0002-9878-3650 Abdolrahman Dadvand https://orcid.org/0000-0002-6642-6122 Martin Wörner https://orcid.org/0000-0003-4630-9292 Holger Marschall https://orcid.org/0000-0001-  ... 
doi:10.5445/ir/1000149252 fatcat:le2jj652qjhnvheq5gh5focsz4

‫آن‬ ‫رﻓﺘﺎر‬ ‫ﺑﺮ‬ ‫ﻏﺸﺎء‬ ‫ﯾﮏ‬ ‫اوﻟﯿﻪ‬ ‫ﻣﻮﻗﻌﯿﺖ‬ ‫ﺗﺄﺛﯿﺮ‬ ‫و‬ ‫ارﺗﺠﺎﻋﯽ‬ ‫ﻏﺸﺎء‬ ‫ﭼﻨﺪ‬ ‫ﻫﯿﺪرودﯾﻨﺎﻣﯿﮑﯽ‬ ‫اﻧﺪرﮐﻨﺶ‬ ‫ﻣﯿﮑﺮوﮐﺎﻧﺎل‬ ‫ﯾﮏ‬ ‫در‬ Hydrodynamic interaction of multiple flexible membranes and initial position effect of a membrane on its behavior in a microchannel ARTICLE INFORMATION ABSTRACT

Abdolrahman As'ad Alizadeh, Dadvand, Mehdi Bakhshan
2016 Modares Mechanical Engineering   unpublished
Dadvand, M.  ... 
fatcat:c57dxggtt5bbxb7mzewc6ofcf4

‫آن‬ ‫رﻓﺘﺎر‬ ‫ﺑﺮ‬ ‫ﻏﺸﺎء‬ ‫ﯾﮏ‬ ‫اوﻟﯿﻪ‬ ‫ﻣﻮﻗﻌﯿﺖ‬ ‫ﺗﺄﺛﯿﺮ‬ ‫و‬ ‫ارﺗﺠﺎﻋﯽ‬ ‫ﻏﺸﺎء‬ ‫ﭼﻨﺪ‬ ‫ﻫﯿﺪرودﯾﻨﺎﻣﯿﮑﯽ‬ ‫اﻧﺪرﮐﻨﺶ‬ ‫ﻣﯿﮑﺮوﮐﺎﻧﺎل‬ ‫ﯾﮏ‬ ‫در‬ Hydrodynamic interaction of multiple flexible membranes and initial position effect of a membrane on its behavior in a microchannel ARTICLE INFORMATION ABSTRACT

Abdolrahman As'ad Alizadeh, Dadvand, Mehdi Bakhshan
2016 Modares Mechanical Engineering   unpublished
Dadvand, M.  ... 
fatcat:lmtwym4nevar7awfic3bxuphg4