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Article
Publication date: 3 January 2017

Mythili Durairaj, Sivaraj Ramachandran and Rashidi Mohammad Mehdi

The present investigation aims to deal with the study of unsteady, heat-generating/-absorbing and chemically reacting Casson fluid flow over a vertical cone and flat plate…

Abstract

Purpose

The present investigation aims to deal with the study of unsteady, heat-generating/-absorbing and chemically reacting Casson fluid flow over a vertical cone and flat plate saturated with non-Darcy porous medium in the presence of cross-diffusion effects.

Design/methodology/approach

A numerical computation for the governing equations has been performed using implicit finite difference method of Crank–Nicolson type.

Findings

The influence of various physical parameters on velocity, temperature and concentration distributions is illustrated graphically, and the physical aspects are discussed in detail. Numerical results for average skin-friction, Nusselt number and Sherwood number are tabulated for the pertaining physical parameters. Results indicate that Soret and Dufour effects have notable influence on heat and mass transfer characteristics of the fluid when the temperature and concentration gradients are high. It is also observed that the consideration of heat generation/absorption plays a vital role in predicting the heat transfer characteristics of moving fluids.

Research limitations/implications

Consider a two-dimensional, unsteady, free convective flow of an incompressible Casson fluid over a vertical cone and a flat plate saturated with non-Darcy porous medium. The fluid properties are assumed to be constant except for density variations in the buoyancy force term. The fluid flow is moderate and the permeability of the medium is assumed to be low, so that the Forchheimer flow model is applicable.

Practical implications

The flow of Casson fluids (such as drilling muds, clay coatings and other suspensions, certain oils and greases, polymer melts and many emulsions), in the presence of heat transfer, is an important research area because of its relevance in the optimized processing of chocolate, toffee and other foodstuffs.

Social implications

In the heat and mass transfer investigations, the Casson fluid model is found to be accurately applicable in many practical situations in the wings of polymer processing industries and biomechanics, etc.; some prominent examples are silicon suspensions, suspensions of bentonite in water and lithographic varnishes used for printing inks.

Originality/value

The motivation of the present study is to bring out the effects of heat source/sink, Soret and Dufour effects on chemically reacting Casson fluid flow over a vertical cone and flat plate saturated with non-Darcy porous medium. The flow of Casson fluids (such as certain oils and greases, polymer melts and many emulsions) in the presence of heat transfer is an important research area because of its relevance in the optimized processing of chocolate, toffee and other foodstuffs. A numerical computation for the governing equations has been performed using implicit finite difference method of the Crank–Nicolson type.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 4 December 2017

Aurang Zaib, Mohammad Mehdi Rashidi, Ali J. Chamkha and Krishnendu Bhattacharyya

This paper aims to peruse the influence of second law analysis for electrically conducting fluid of a Casson nanofluid over a wedge. For activation energy, a modified…

Abstract

Purpose

This paper aims to peruse the influence of second law analysis for electrically conducting fluid of a Casson nanofluid over a wedge. For activation energy, a modified Arrhenius function is used.

Design/methodology/approach

The highly non-linear governing equations are developed using similarity transformations and then computed numerically via Keller–Box method.

Findings

The influences of emerging parameters on velocity, temperature distribution and concentration of nanoparticle are explained and presented via graphs and tables. Also, the behavior of fluid flow is investigated through the coefficient of skin friction, Nusselt and Sherwood numbers. Results reveal that the velocity profile enhances due to increasing Casson parameter and magnetic parameter, whereas the temperature distribution and concentration of nanoparticle decrease with larger vales of Casson parameter. It is inspected that the concentration boundary layer increases due to activation energy and decreases due to reaction rate and temperature differences.

Originality/value

The authors believe that all the numerical results are original and significant which are used in biomedicine, industrial, electronics and transportation. The results have not been considered elsewhere.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 12
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 6 November 2018

Aurang Zaib, Rizwan Ul Haq, Ali J. Chamkha and Mohammad Mehdi Rashidi

The purpose of this paper is to present an inclusive study of the mixed convective flow involving micropolar fluid holding kerosene/water-based TiO2 nanoparticle towards a…

Abstract

Purpose

The purpose of this paper is to present an inclusive study of the mixed convective flow involving micropolar fluid holding kerosene/water-based TiO2 nanoparticle towards a vertical Riga surface with partial slip. The outcomes are confined for opposing and assisting flows.

Design/methodology/approach

Similarity equations are acquired and then worked out numerically by the Keller box technique.

Findings

Impacts of significant parameters on microrotation velocity, temperature distribution, velocity profile together with the Nusselt number and the skin friction are argued with the help of graphs. Two solutions are achieved in opposing flow, while the solution is unique in assisting flow. It is also monitored that the separation of boundary layer delays because of micropolar parameter and accelerates because of volume fraction.

Originality/value

The authors trust that all these results are new and significant for researchers.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 9 November 2018

Yuan Ma, Rasul Mohebbi, Mohammad Mehdi Rashidi and Zhigang Yang

This paper aims to numerically investigate the natural convection heat transfer of multi-wall carbon nanotubes (MWCNTs)-water nanofluid in U-shaped enclosure equipped with…

Abstract

Purpose

This paper aims to numerically investigate the natural convection heat transfer of multi-wall carbon nanotubes (MWCNTs)-water nanofluid in U-shaped enclosure equipped with a hot obstacle by using the lattice Boltzmann method.

Design/methodology/approach

The combination of the three topics (U-shaped enclosure, different positions of the hot obstacle and MWCNTs-water nanofluid) is innovative in the present study. In total, 15 different positions of the hot obstacle have been arranged, and the effects of pertinent parameters such as Rayleigh numbers, the solid volume fraction of the MWCNTs nanoparticles on the flow field, temperature distribution and the rate of heat transfer inside the enclosure are also investigated.

Findings

It is found that the average Nusselt number increased by raising the Rayleigh number, and so did the nanoparticle solid volume fraction regardless the position of the hot obstacle. Moreover, enclosures where the hot obstacle is located at the bottom region proved to provide a better rate of heat transfer at high Rayleigh number (106). It is concluded that at a low Ra number (103-105), the higher heat transfer rate and Nu number will be obtained when the hot obstacle is located in the left or right channel.

Originality/value

In the literature, no trace of studying the natural convection of nanofluids in U-shaped enclosures with heating obstacles was found. Also, MWCNTs were less used as nanoparticles. As the natural convection of nanofluids in thermal engineering applications would expand the existing knowledge, the current researchers conducted a numerical study of the natural convection of Maxwell nanofluid with MWCNTs in U-shaped enclosure equipped with a hot obstacle by using lattice Boltzmann method.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 15 October 2018

Aydin Zehforoosh, Siamak Hossainpour and Mohammad Mehdi Rashidi

The purpose of this study is to indicate the effect of mounting heat generating porous matrix in a close cavity on the Brownian term of CuO-water nanofluid and its impact…

Abstract

Purpose

The purpose of this study is to indicate the effect of mounting heat generating porous matrix in a close cavity on the Brownian term of CuO-water nanofluid and its impact on improving the Nusselt number.

Design/methodology/approach

Because of the presence of heat source in porous matrix, couple of energy equations is solved for porous matrix and nanofluid separately. Thermal conductivity and viscosity of nanofluid were assumed to be consisting of a static component and a Brownian component that were functions of volume fraction of the nanofluid and temperature. To explain the effect of the Brownian term on the flow and heat fields, different parameters such as heat conduction ratio, interstitial heat transfer coefficient, Rayleigh number, concentration of nanoparticles and porous material porosity were investigated and compared to those of the non-Brownian solution.

Findings

The Brownian term caused the cooling of porous matrix because of rising thermal conductivity. Mounting the porous material into cavity changes the temperature distribution and increases Brownian term effect and heat transfer functionality of the nanofluid. Besides, the effect of the Brownian term was seen to be greatest at low Rayleigh number, low-porosity and small thermal conductivity of the porous matrix. It is noteworthy that because of decrement of thermal conduction in high porosities, the impact of Brownian term drops severely making it possible to obtain reliable results even in the case of neglecting Brownian term in these porosities.

Originality/value

The effect of mounting the porous matrix with internal heat generation was investigated on the improvement of variable properties of nanofluid.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 10 December 2020

Endalkachew Getachew Ushachew, Mukesh Kumar Sharma and Mohammad Mehdi Rashidi

The purpose of this study is to explore the heat transfer enhancement in copper–water nanofluid flowing in a diagonally vented rectangular enclosure with four discrete…

Abstract

Purpose

The purpose of this study is to explore the heat transfer enhancement in copper–water nanofluid flowing in a diagonally vented rectangular enclosure with four discrete heaters mounted centrally on the sidewalls and a square-shaped embedded heated block in the influence of a static magnetic field.

Design/methodology/approach

Four discrete heaters are mounted centrally on each sidewall of the rectangular enclosure that embraces a heated square block. A static transverse magnetic field is acting on the vertical walls. The Navier–Stokes equations of motion and the energy equation are modified by incorporating Lorentz force and basic physical properties of nanofluid. The derived momentum and energy equations are tackled numerically using the successive over-relaxation technique associating with the Gauss–Seidel iteration technique. The effects of physical parameters connected to dynamics of flow and heat convection are explored from streamlines and isotherms graphs and discussed numerically in terms of Nusselt number.

Findings

The effect of the embedded heated square block size and its location in the enclosure, nanoparticles volume fraction and the intensity of the magnetic field on flow and heat transfer are computed. Compared with the case when no heated block is embedded in the enclosure, in free convection at Ra = 106, the average local Nusselt number on the wall-mounted heaters is attenuated by 8.25%, 11.24% and 12.75% when the enclosure embraced a heated square block of side length 10% of H, 20% of H and 30% of H, respectively. An increase in Hartmann number suppresses the heat convection.

Research limitations/implications

The enhancement in the convective heat is greater when the buoyancy effect dominates the viscous effects. Placing the embedded heated block near the inlet vent, the lower temperature zone has reduced while the embedded heated block is at the central location of the enclosure, the high-temperature zone has expanded. The external magnetic field can be used as a non-invasive controlling device.

Practical implications

The numerically simulated results for heat convection of water-based copper nanofluid agreed qualitatively with the existing experimental results.

Social implications

The models could be used in designing a target-oriented heat exchanger.

Originality/value

The paper includes a comparative study for three locations of the embedded heated square. The optimal results for the centrally located heated block are also performed for three different sizes of the embedded block. The numerically simulated results are compared with the published numerical and experimental studies.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 18 May 2020

Yuan Ma, Mohammad Mehdi Rashidi, Rasul Mohebbi and Zhigang Yang

The nanofluid natural convection heat transfer in a hollow complex enclosure, which is named as Shamse knot shape, is studied numerically. This paper aims to present how…

Abstract

Purpose

The nanofluid natural convection heat transfer in a hollow complex enclosure, which is named as Shamse knot shape, is studied numerically. This paper aims to present how the Rayleigh number, nanoparticle volume fraction, Hartmann number and hollow side length affect the fluid flow and heat transfer characteristics.

Design/methodology/approach

The continuity, momentum and energy equations have been solved using lattice Boltzmann method (LBM). Numerical simulation has been obtained for a wide range of Rayleigh number (103 ≤ Ra ≤ 106), nanoparticle volume fraction (0 ≤ ϕ 0.05) and Hartmann number (0 ≤ Ha ≤ 60) to analyze the fluid flow pattern and heat transfer characteristics. Moreover, the effect of hollow side length (D) on flow field and thermal performance is studied.

Findings

The results showed that the magnetic field has a negative effect on the thermal performance and the average Nusselt number decreases by increasing the Hartmann number. Because of the high conduction heat transfer coefficient of nanoparticles, the average Nusselt number increases by rising the nanoparticle volume fraction. The effect of adding nanoparticles on heat transfer is more effective at low nanoparticle volume fraction (0 ≤ ϕ ≤ 0.01). It was also found that at Ra = 106, when the hollow side length increases to 3, the flow pattern becomes different due to the small gap. The averaged Nu is an increasing function of D at low Ra and an opposite trend occurs at high Rayleigh number.

Originality/value

For the first time, the effects of magnetic field, Rayleigh number, nanoparticle volume fraction and hollow side length on natural convection heat transfer of hybrid nanofluid (Ag-TiO2/water) is investigated in a complicated cavity.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 4 December 2017

Mahmoud Salari, Mohammad Mehdi Rashidi, Emad Hasani Malekshah and Masoud Hasani Malekshah

Because the local Re numbers, ratio of inertia to viscous forces, are not same at different regions of the enclosures, the present study aims to deal with the influences…

Abstract

Purpose

Because the local Re numbers, ratio of inertia to viscous forces, are not same at different regions of the enclosures, the present study aims to deal with the influences of using the turbulent/transition models on numerical results of the natural convection and flow field within a trapezoidal enclosure.

Design/methodology/approach

The three-dimensional (3D) trapezoidal enclosure with different inclined side walls of 75, 90 and 105 degrees are considered, where the side walls are heated and cooled at Ra = 1.5 × 109 for all cases. The turbulent models of the k-ε-RNG, k- ω-shear-stress transport (SST) and the newly developed transition/turbulent model of Reθ-γ-transition SST are utilized to analyze the fluid flow and heat transfer characteristics within the enclosure and compared their results with validated results.

Findings

Comprehensive comparisons have been carried out for all cases in terms of flow and temperature fields, as well as turbulent quantities, such as turbulent kinetic energy and turbulent viscosity ratio. Furthermore, the velocity and thermal boundary layers have been investigated, and the approximate transition regions for laminar, transitional and turbulent regimes have been determined. Finally, the heat transfer coefficient and skin friction coefficient values have been presented and compared in terms of different turbulent models and configurations. The results show that the transition/turbulence model has better prediction for the flow and heat fields than fully turbulent models, especially for local parameters for all abovementioned governing parameters.

Originality value

The originality of this work is to analyze the 3D turbulent/transitional natural convection with different turbulence/transition models in a trapezoidal enclosure.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 12
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 18 April 2017

Syed Tauseef Mohyud-din, Naveed Ahmed, Umar Khan and Mohammad Mehdi Rashidi

The purpose of this study is to analyze thermo-diffusion and diffusion-thermo effects, combined with first-order chemical reaction, in the flow of a micropolar fluid…

Abstract

Purpose

The purpose of this study is to analyze thermo-diffusion and diffusion-thermo effects, combined with first-order chemical reaction, in the flow of a micropolar fluid through an asymmetric channel with porous boundaries. Suction/injection velocities of upper and lower walls are taken to be different from each other. The channel exhibits a parting or embracing motion and the fluid enters, or leaves, the channel because of suction/injection through the permeable walls.

Design/methodology/approach

The solution of the problem is obtained by using the fourth-order Runge-Kutta method combined with the shooting technique.

Findings

The asymmetric nature of the channel that is caused by the different permeabilities of the walls deeply influences the flow. The temperature of the fluid rises significantly by increasing the absolute value of A for both Case I and Case II. While, for the concentration profile, the concentration drops near the lower vicinity of the center in Case I, and, it falls near the lower wall of the channel in Case II. Stronger Dufour effects increase the temperature of the fluid except for Case 1 at the center of the channel and for Case II in lower quarter of the channel.

Originality/value

It is confirmed that the presented work is original and is not under consideration by any other journal.

Details

Engineering Computations, vol. 34 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 2 November 2018

Alireza Rahimi, Abbas Kasaeipoor, Emad Hasani Malekshah, Mohammad Mehdi Rashidi and Abimanyu Purusothaman

This study aims to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with CuO-water nanofluid.

Abstract

Purpose

This study aims to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with CuO-water nanofluid.

Design/methodology/approach

The lattice Boltzmann method is used to solve the problem numerically. Two different multiple relaxation time (MRT) models are used to solve the problem. The D3Q7–MRT model is used to solve the temperature field, and the D3Q19 is used to solve the fluid flow of natural convection within the enclosure.

Findings

The influences of different Rayleigh numbers (103 < Ra < 106) and solid volume fractions (0 < f < 0.04) on the fluid flow, heat transfer, total entropy generation, local heat transfer irreversibility and local fluid friction irreversibility are presented comprehensively. To predict thermo–physical properties, dynamic viscosity and thermal conductivity, of CuO–water nanofluid, the Koo–Kleinstreuer–Li (KKL) model is applied to consider the effect of Brownian motion on nanofluid properties.

Originality/value

The originality of this work is to analyze the three-dimensional natural convection and entropy generation using a new numerical approach of dual-MRT-based lattice Boltzmann method.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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