Computational Fluid Dynamics (CFD)
Kandassamy K; Prabu Balakrishnan
Articles in Press, Accepted Manuscript, Available Online from 21 April 2020
Abstract
Heat dissipation in electronic circuits is important to maintain their reliability and functionality. In this work micro-channel based bio-inspired flow field models are proposed and numerically analyzed. The proposed flow fields have single to four, inlet-outlet pairs. COMSOL is used to do the numerical ...
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Heat dissipation in electronic circuits is important to maintain their reliability and functionality. In this work micro-channel based bio-inspired flow field models are proposed and numerically analyzed. The proposed flow fields have single to four, inlet-outlet pairs. COMSOL is used to do the numerical analysis. Conjugate heat transfer analysis is done on the quarter sectional models, utilizing bi-axial symmetry of the flow fields to reduce computational cost. Constant heat flux is applied to the base of the proposed heat sinks. The results show that, the thermal and hydraulic resistances of the proposed models are lower than traditional micro-channel arrays. The four inlet-outlet pairs, model shows a thermal resistance of 0.121 to 0.158 C/W at constant Re inlet condition, achieved with a pumping power of 0.102-0.126W. Two and four, inlet-outlet pair models with aspect ratio 8.6 have a thermal resistance of 0.069 and 0.067 C/W, for pumping powers 2.078 and 4.365W respectively. The pressure drop of the proposed models is lower than conventional microchannel arrays.
Computational Fluid Dynamics (CFD)
Ali Akbar rashidi; Ehsan Kianpour
Articles in Press, Accepted Manuscript, Available Online from 08 January 2019
Abstract
Natural convection heat transfer is studied numerically in a triangular enclosure. The enclosure is isosceles right triangle and its bottom wall is hot, the hypotenuse is cold and the other wall is adiabatic. Also, a vertical magnetic field is applied in the enclosure, and there is hybrid nanofluid inside ...
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Natural convection heat transfer is studied numerically in a triangular enclosure. The enclosure is isosceles right triangle and its bottom wall is hot, the hypotenuse is cold and the other wall is adiabatic. Also, a vertical magnetic field is applied in the enclosure, and there is hybrid nanofluid inside the enclosure. This study is conducted for Rayleigh numbers of 103-105, the Hartmann numbers between 0-80, and the volume fraction of nanofluid is between 0-2 percent. Based on the obtained results, as the Hartmann number augments, the temperature of the center of the enclosure decreases due to weakening of the heat transfer flow by increasing the magnetic field forces. In addition, as the Hartmann number augments, the streamlines approach to the walls because the horizontal momentum forces decrease when the Hartmann number increases. Furthermore, by increasing the density of nanoparticles, the heat transfer rate increase, and as a result, heat transfer builds up. Finally, heat transfer improve when the hybrid-nanofluid is employed rather than ordinary nanofluid.
Computational Fluid Dynamics (CFD)
Milad Darabi Boroujeni; Ehsan Kianpour
Articles in Press, Accepted Manuscript, Available Online from 23 January 2019
Abstract
In this study, cooling of a hot obstacle in a rectangular cavity filled with water-CuO nanolfuid has been examined numerically. This cavity has an inlet and outlet and the cold nanofuid comes from the left side of the cavity and after cooling the hot obstacle, it goes out from the opposite site. All ...
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In this study, cooling of a hot obstacle in a rectangular cavity filled with water-CuO nanolfuid has been examined numerically. This cavity has an inlet and outlet and the cold nanofuid comes from the left side of the cavity and after cooling the hot obstacle, it goes out from the opposite site. All of the walls are insulated, and the SIMPLER algorithm has been employed for solving the governing equations. The effects of fluid inertia, magnetic field strength, volume fraction of nanoparticles, and the place of outlet on heat transfer rate has been scrutinized. According to the results, the average Nusselt number builds up as the outlet place goes down. In other words, when the outlet is located at the bottom of the cavity, the rate of the heat transfer is maximum. Moreover, by increasing the Reynolds number and volume fraction of nanoparticles, the average Nusselt number builds up as well.
Computational Fluid Dynamics (CFD)
Omid Khayat; Hossein Afarideh
Articles in Press, Accepted Manuscript, Available Online from 15 April 2019
Abstract
One of the challenging problems in the Oil & Gas industry is accurate and reliable multiphase flow rate measurement in a three-phase flow. Application of methods with minimized uncertainty is required in the industry. Previous developed correlations for two-phase flow are complex and not capable ...
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One of the challenging problems in the Oil & Gas industry is accurate and reliable multiphase flow rate measurement in a three-phase flow. Application of methods with minimized uncertainty is required in the industry. Previous developed correlations for two-phase flow are complex and not capable of three-phase flow. Hence phase behavior identification in different conditions to designing and modeling of three-phase flow is important. Numerous laboratory and theoretical studies have been done to describe the Venturi multiphase flow meter in both horizontal and vertical flow. However, it is not possible to select the measurement devices for all similar conditions. In this study a new venturi model was developed that implemented in Simulink/Matlab for predicting mass flow rate of gas, water and oil. This models is simple and semilinear. Several classified configurations of three phase flow were simulated using Computational Fluid Dynamics (CFD) analysis to get hydrodynamics parameters of the flows to use as inputs of the model. The obtained data, used as test and train data in Least squares support vector machine (LSSVM) algorithm. The pressure drop, mass flow rate of gas, oil and water have been calculated with LSSVM method. Two tuning parameters of LSSVM, namely γ and σ^2, obtained as 1150954 and 0.4384, 53.9199 and 0.18163, 8.8714 and 0.14424, and 10039130.2214 and 0.74742 for pressure drop, mass flow rate of oil, gas mass flow rate, water mass flow rate, respectively. Developed models was found to have an average relative error of 5.81%, 6.31% and 2.58% for gas, oil and water respectively.
Computational Fluid Dynamics (CFD)
Shuvam Mohanty; Om Parkash; Rajesh Arora
Articles in Press, Accepted Manuscript, Available Online from 25 August 2019
Abstract
This paper presents a comprehensive and exclusive thermodynamic analysis of counter flow heat exchanger under various operating and geometrical conditions. Analysis system (ANSYS) workbench 14.0 has been used for computational analysis and comparison with previous literature has been carried out in view ...
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This paper presents a comprehensive and exclusive thermodynamic analysis of counter flow heat exchanger under various operating and geometrical conditions. Analysis system (ANSYS) workbench 14.0 has been used for computational analysis and comparison with previous literature has been carried out in view of variable temperature and mass flow rate of hot and cold fluids. An analytical and statistical method of computational fluid dynamics (CFD) analysis is used for simulation and validation of the heat exchanger under steady and dynamic operating conditions. A 3-D model of a heat exchanger having 1000 mm and 1200 mm outside and inside tube lengths with diameter 12.7 mm is designed in ANSYS environment using Renormalization Group (RNG) k-ε approach in order to get the better effectiveness of the system. The variable effects of the steady-state temperature and mass flow rate are investigated. The influence of turbulence over the temperature and pressure profiles is also studied. Moreover, the analytical outcome of the present investigations is compared with that of previous existing literature and found to be in agreement with the previous studies. The proposed analysis presents an in-depth perspective and simulation of temperature gradient profile through the length of heat exchanger. The proposed modified design of heat exchanger along with changing flow direction yields much better results with small computational error 0.66% to 1.004% and 0.83% to 1.05% with respect to change in temperature and mass flow rate respectively.
Computational Fluid Dynamics (CFD)
mohammad saeed sharifi; Miralam Mahdi; Karim Maghsoudi Mehraban
Volume 9, Issue 1 , Summer and Autumn 2019, , Pages 107-119
Abstract
The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an ...
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The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an optimal design of the air conditioning system. In this study, a chamber was first constructed and the temperature distribution inside it was measured. There was a fan installed at the back of the chamber for drainage. At the chamber entrance, three inlet for entering the flow were considered. The air from the middle inlet was heated by a heater. To prevent heat loss, the body of the enclosure was insulated. Several temperature sensors were installed at certain positions of the chamber for temperature measurement. Using Fluent software, the model of a full-sized chamber was created. Meshing is a hybrid and was used as a boundary layer Mesh. The inlet and outlet temperature of the chamber and the air output rates as boundary conditions were used in the simulation. Numerical analysis for K-ε and K-ω turbulence models was performed and different wall conditions were investigated. The numerical simulation results were in good agreement with the measurement results. Using the K-ε turbulence model with a scalable wall function had a better accuracy than other models. Changes in velocity and temperature were presented in graphs and contours at different positions of the compartment.
Computational Fluid Dynamics (CFD)
Seyed Masoud Vahedi; Mohammad Sadegh Valipour; Filippo de Monte
Volume 9, Issue 1 , Summer and Autumn 2019, , Pages 1-18
Abstract
Arterial drug concentration distribution determines local toxicity. The safety issues dealt with Drug-Eluting Stents (DESs) reveal the needs for investigation about the effective factors contributing to fluctuations in arterial drug uptake. The current study focused on the importance of hypertension ...
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Arterial drug concentration distribution determines local toxicity. The safety issues dealt with Drug-Eluting Stents (DESs) reveal the needs for investigation about the effective factors contributing to fluctuations in arterial drug uptake. The current study focused on the importance of hypertension as an important and controversial risk factor among researchers on the efficacy of Heparin-Eluting Stents (HES). For this purpose, the effect of blood pressure is systematically investigated in certain cardiac cycle modes. A comprehensive study is conducted on two classes, pulsatile (time-dependent), to have a more realistic simulation, and non-pulsatile (time-independent) blood flow, each one in four modes. The governing equations applied to drug release dynamics are obtained based on porous media theory. The equations are solved numerically using Finite Volume Method (FVM). Results reveal that there is a significant difference when the plasma flow considered and when it is neglected (regardless of time dependency). Moreover, the concentration level is more decreased in pulsatile blood flow rather than the non-pulsatile blood flow, although the penetration depth for pressure and concentration are nearly 20% and 5% of the wall thickness, respectively. In other words, the mass experienced by the arterial wall is lower in pulsatile blood flow in comparison to non-pulsatile blood flow. As a consequence, the risk of toxicity is declined as the blood pressure increases. Also, it can be seen that the polymer is diffusion-dominated so that no significant changes in the release characteristics are observed in the presence of the plasma filtration.
Computational Fluid Dynamics (CFD)
S. Harimi; Azam Marjani
Volume 9, Issue 1 , Summer and Autumn 2019, , Pages 33-45
Abstract
The present work deals with heat transfer characteristics as well as fluid flow patterns in laminar flow regime for a circular cylinder with six control rods arranged in equilateral triangular geometries. The computations have been carried out by a finite volume approach using the overset grid method. ...
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The present work deals with heat transfer characteristics as well as fluid flow patterns in laminar flow regime for a circular cylinder with six control rods arranged in equilateral triangular geometries. The computations have been carried out by a finite volume approach using the overset grid method. The unsteady flow at Re= 200 and Pr= 0.7 and 7.0 was examined. The effect of the control rods on suppression of the fluid forces applied on a main cylinder has been investigated by numerical solution of the Navier-Stokes equations. Based on the results obtained, the arrangement employed in this study indicated the significant performance in reducing the oscillatory force coefficients of the primary cylinder. Except for some gap ratios, it is indicated that both drag and lift coefficients are much lower than that for a single cylinder. Moreover, forced convection heat transfer was calculated using local and mean Nusselt numbers at the surface of the cylinders. The instantaneous streamlines, the vortices and isothermal contours were presented in order to analyze the temperature field and flow field around the cylinders.
Computational Fluid Dynamics (CFD)
brahim Rostane; ALIANE KHALED; said Abboudi
Volume 9, Issue 1 , Summer and Autumn 2019, , Pages 77-87
Abstract
The aim of our study is to analyze the impact of insertion holes in the middle of obstacles on the flow around a surface-mounted cube, In order to do this; we studied four configurations of obstacles in a channel with a Reynods number based on obstacle height ReH = 40000. The hexahedral structured meshes ...
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The aim of our study is to analyze the impact of insertion holes in the middle of obstacles on the flow around a surface-mounted cube, In order to do this; we studied four configurations of obstacles in a channel with a Reynods number based on obstacle height ReH = 40000. The hexahedral structured meshes were used to solve the fluid dynamics equations .The finite volume method are employed to solve the governing equations using the ANSYS CFX code and the turbulence model k-ω SST. The streamwise velocity profiles, the Time-averaged streamlines, the turbulence kinetic energy and the drag coefficient are presented. The results showed the appearance of a second vortex behind obstacles with hole from diameter D/H=0.2. The turbulence kinetic energy was greater on top of the obstacle, it was more intense for the obstacle without hole, this intensity decreased as the hole diameter increased. The drag coefficient was improved only for the case D/H=0.32
Computational Fluid Dynamics (CFD)
Tohid Adibi
Volume 8, Issue 2 , Winter and Spring 2019, , Pages 223-234
Abstract
In this paper the characteristics of unsteady three-dimensional incompressible flows with heat transfer are obtained along with artificial compressibility of Chorin. At first, compatibility equations and pseudo characteristics for three-dimensional flows are derived from five governing equations (continuity ...
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In this paper the characteristics of unsteady three-dimensional incompressible flows with heat transfer are obtained along with artificial compressibility of Chorin. At first, compatibility equations and pseudo characteristics for three-dimensional flows are derived from five governing equations (continuity equation, Momentum equations in three directions, and energy equation) and then results are simplified to two dimensional flows. Pseudo Mach hyper-cone (four dimensional cone) are found and its cross-section with physical axis is calculated numerically. Unlike compressible flow, this is not a sphere. It is found that the pseudo acoustic speed within the incompressible flow is function of artificial compressibility parameter and the directions. In two dimensional, Pseudo Mach cone is obtained by numerical solution of characteristic equations. Unlike compressible flow, the cross section of Mach cone with x-y plane is not circle. This shape is not oval, too. The influence of artificial compressibility parameter on convergence history and accuracy was surveyed by simulation of cavity flow as a benchmark
Computational Fluid Dynamics (CFD)
Muhim Chutia
Volume 8, Issue 1 , Summer and Autumn 2018, , Pages 75-84
Abstract
The aim of this paper is to investigate the effect of the variable thermal conductivity and the inclined uniform magnetic field on the plane Poiseuille flow of viscous incompressible electrically conducting fluid between two porous plates Joule heating in the presence of a constant pressure gradient ...
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The aim of this paper is to investigate the effect of the variable thermal conductivity and the inclined uniform magnetic field on the plane Poiseuille flow of viscous incompressible electrically conducting fluid between two porous plates Joule heating in the presence of a constant pressure gradient through non-uniform plate temperature. It is assumed that the fluid injection occurs at lower plate and fluid suction occurs at upper plate. The governing equations of momentum and energy are transformed into coupled and nonlinear ordinary differential equations using similarity transformation and then solved numerically using finite difference technique. Numerical values for the velocity and temperature have been iterated by Gauss Seidal iteration method in Matlab programming to a suitable number so that the convergent solutions of velocity and temperature are considered to be achieved. Numerical results for the dimensionless velocity and the temperature profiles for different governing parameters such as the Hartmann Number (M) angle of inclination of magnetic field (α), suction Reynolds number (Re) Prandtl Number (Pr), Eckert number (Ec) and variable thermal conductivity (ԑ) have been discussed in detail and presented through graphs.
Computational Fluid Dynamics (CFD)
Sandeep Naramgari; Siva Krishnam Raju C; G. Kumaran
Volume 7, Issue 2 , Winter and Spring 2018, , Pages 209-222
Abstract
This study deals with the three-dimensional flow of a chemically reacting magnetohydrodynamic Sisko fluid over a bidirectional stretching surface filled with the ferrous nanoparticles in the presence of non-uniform heat source/sink, nonlinear thermal radiation, and suction/injection. After applying the ...
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This study deals with the three-dimensional flow of a chemically reacting magnetohydrodynamic Sisko fluid over a bidirectional stretching surface filled with the ferrous nanoparticles in the presence of non-uniform heat source/sink, nonlinear thermal radiation, and suction/injection. After applying the self-suitable similarity transforms, the nonlinear ordinary differential equations are solved numerically using Runge-Kutta and Newton’s methods. Results present the effects of various non-dimensional governing parameters on velocity, temperature and concentration profiles. Also, computed and discussed the friction factor coefficients along with the local Nusselt and Sherwood numbers. Similarity solutions for suction and injection cases are presented. A good agreement in the present results with the existed literature under some special limited cases is found. It is found that heat and mass transfer performance of Sisko ferrofluid is significantly high in injection case when compared with the suction case. Increasing values of the stretching parameter enhance the heat and mass transfer rate.
Computational Fluid Dynamics (CFD)
chakravarthula S K Raju; P DurgaPrasad; S.V.K. Varma
Volume 7, Issue 2 , Winter and Spring 2018, , Pages 137-150
Abstract
In this study, the Brownian motion and thermophoresis effects on the MHD ferrofluid flow over a cone with thermal radiation were discussed. Kerosene with the magnetic nanoparticles (Fe3O4) was considered. A set of transformed governing nonlinear coupled ordinary differential equations were solved numerically ...
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In this study, the Brownian motion and thermophoresis effects on the MHD ferrofluid flow over a cone with thermal radiation were discussed. Kerosene with the magnetic nanoparticles (Fe3O4) was considered. A set of transformed governing nonlinear coupled ordinary differential equations were solved numerically using Runge-Kutta based shooting technique. A simulation was performed by mixing ferrous particles with base fluids. Also, dual solutions for Casson Ferrofluid flow over a cone with rotation and without rotation effects were presented. An agreement of the present solutions with those published in literature was found. The effect of dimensionless parameters on velocity, temperature and concentration profiles along with the friction factor coefficients, Nusselt number, and the Sherwood numbers were discussed with the help of graphs and tables. It was found that the volume fraction of Ferro nanoparticles, magnetic field parameter, and Brownian motion parameters are controlling the friction factor coefficients, Nusselt number and Sherwood numbers for both the rotation and without rotation effects cases.
Computational Fluid Dynamics (CFD)
Siamak Gharahjeh; Ammar Ashraf; Ghorban Mahtabi
Volume 7, Issue 2 , Winter and Spring 2018, , Pages 151-160
Abstract
In this study, a numerical solution of 2D steady incompressible lid-driven cavity flow is presented. Three different numerical schemes were employed to make a comparison on the practicality of the methods. An alternating direction implicit scheme for the vorticity-stream function formulation, explicit ...
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In this study, a numerical solution of 2D steady incompressible lid-driven cavity flow is presented. Three different numerical schemes were employed to make a comparison on the practicality of the methods. An alternating direction implicit scheme for the vorticity-stream function formulation, explicit and implicit schemes for the primitive variable formulation of governing Navier-Stokes equations were attempted. A fairly fine uniform grid was adopted for all the cases after a technical procedure was applied to come up with the proper mesh size that would make the solution roughly independent of mesh quality. The solutions obtained for different Reynolds numbers are presented and compared. Superiority of numerical approaches was investigated and compared to benchmark solutions available in the literature. Based on the results of the present research, it can be claimed that explicit scheme used for primitive variable formulation can be only half the way (as in Re=2500 for explicit to Re=5000 for ADI and implicit schemes) as successful as the other two numerical methods due to its relative simplicity.
Computational Fluid Dynamics (CFD)
Ghanbarali Sheikhzadeh; Mahdi Mollamahdi; Mahmoud Abbaszadeh
Volume 7, Issue 2 , Winter and Spring 2018, , Pages 161-173
Abstract
In this study, the momentum and energy equations of laminar flow of a non-Newtonian fluid are solved in an axisymmetric porous channel using the least square and Galerkin methods. The bottom plate is heated by an external hot gas, and a coolant fluid is injected into the channel from the upper plate. ...
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In this study, the momentum and energy equations of laminar flow of a non-Newtonian fluid are solved in an axisymmetric porous channel using the least square and Galerkin methods. The bottom plate is heated by an external hot gas, and a coolant fluid is injected into the channel from the upper plate. The arising nonlinear coupled partial differential equations are reduced to a set of coupled nonlinear ordinary differential equations using stream function.These equations can be solved using the different numerical method. The numerical solution is conducted using fourth order Rung-Kutta method. With comparing the results obtained from the analytical and numerical methods, a good adaptation can be seen between them. It can also be observed that the results of the Galerkin method have further conformity with the numerical results and the Galerkin method is simpler than the least square method and requires fewer computations. The effects of Reynolds number, Prandtl number and power law index of non-Newtonian fluid is examined on flow field and heat transfer. The results show that Nusselt number increases by increasing Reynolds number, Prandtl number, and power law index.
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