Composite Materials
Y. Bayat; H. Ekhteraei Toussi
Abstract
In many cases, a torsional shaft may be a thick-walled radially inhomogeneous cylindrical object. The hollow shafts made of functionally graded materials (FGMs) are such kind of compositions which were studied in this paper. Cylindrical FG shafts are composed of ceramic and metallic parts with power ...
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In many cases, a torsional shaft may be a thick-walled radially inhomogeneous cylindrical object. The hollow shafts made of functionally graded materials (FGMs) are such kind of compositions which were studied in this paper. Cylindrical FG shafts are composed of ceramic and metallic parts with power function distribution across the radial direction. The ceramic phase is isotropic elastic and the metallic phase was elastic-plastic. In this paper, the volume fraction-based elastic–plastic mixture rule of renowned Tamura–Tomota–Ozawa (TTO) was used to model the behavior of the composite material. The elasto-plastic torsion problem was modeled and solved analytically. The results were compared with the simulations of ABAQUS and the accuracy of the solutions was evaluated. Depending on the thickness and level of inhomogeneity, different modes of yielding were obtained. The results showed that plastic zone could occur at the inner or outer surfaces or simultaneously at both surfaces; even it may start in-between the thickness. Moreover, the influence of material inhomogeneity and thickness of shaft upon the plastic zone development were studied and discussed.
Fluid Mechanics
Rahim Shamsoddini
Abstract
Liquid sloshing is a common phenomenon in the transporting of liquid tanks. Liquid waves lead to fluctuating forces on the tank wall. If these fluctuations are not predicted or controlled, they can lead to large forces and momentum. Baffles can control liquid sloshing fluctuations. One numerical method, ...
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Liquid sloshing is a common phenomenon in the transporting of liquid tanks. Liquid waves lead to fluctuating forces on the tank wall. If these fluctuations are not predicted or controlled, they can lead to large forces and momentum. Baffles can control liquid sloshing fluctuations. One numerical method, widely used to model the liquid sloshing phenomena is Smoothed Particle Hydrodynamics (SPH). Because of its Lagrangian nature, SPH is suitable for simulating free surface flow. In the present study, a relatively accurate Incompressible SPH (ISPH) method improved by kernel gradient correction tensors, particle shifting algorithms, turbulence viscosity calculations, and free surface particle detectors is applied for the free surface flow modeling. In comparison to the other SPH Simulations and experimental data, these results show that the present algorithm is effective for simulating free surface problems. The present algorithm has been applied to simulate liquid sloshing phenomena, while the aim of this study is the investigation of vertical and horizontal baffle effects on the control and damping of liquid sloshing. Results show that for vertical baffles, baffle size has a major role in sloshing fluctuation damping. For horizontal baffles, also including size, the baffle base position has a significant role in liquid sloshing fluctuation damping. When horizontal baffle is near the free surface, sloshing fluctuation-damping increases.
Computational Fluid Dynamics (CFD)
Alireza Alinezhad; Ataallah Soltani Goharrizi; Ataallah Kamyabi
Abstract
In this paper, heat transfer and fluid flow around a solid cylinder wrapped with a porous layer in the channel were studied numerically by computational fluid dynamics (CFD). The homogeneous concentric and eccentric porous medium round a rigid, solid cylinder are supposed at local thermal equilibrium. ...
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In this paper, heat transfer and fluid flow around a solid cylinder wrapped with a porous layer in the channel were studied numerically by computational fluid dynamics (CFD). The homogeneous concentric and eccentric porous medium round a rigid, solid cylinder are supposed at local thermal equilibrium. The transport phenomena within the porous layer, volume averaged equations were employed, however the conservation laws of mass, momentum and energy were applied in the channel. The main purpose of this study is analyzed and compared the heat flux of concentric and eccentric porous layer in Reynolds number range of 1 to 40 and Darcy numbers of 10-2 to 10-6. It is found that with the decline of Darcy number, the vortex length is increased behind the solid cylinder surface. In addition, the heat flux rate of the cylinder is raised with the increase of Reynolds number. Finally, the results showed that the average Nusselt numbers in different Darcy and Reynolds numbers are higher in the eccentric porous layer than in the concentric porous layer. For example, our findings show that in Da=〖10〗^(-5), Re=40 and d=0.07 m, the average Nusselt number in the eccentric porous layer is 7.5% higher than the concentric porous layer.
Biomechanics
Mehdi Jahangiri; Mohsen Saghafian; Mahmood Reza Sadeghi
Abstract
A numerical study of hemodynamic parameters of pulsatile blood flow is presented in a stenotic artery with A numerical study of hemodynamic parameters of pulsatile blood flow is presented in a stenotic artery with non-Newtonian models using ADINA. Blood flow was considered laminar, and the arterial wall ...
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A numerical study of hemodynamic parameters of pulsatile blood flow is presented in a stenotic artery with A numerical study of hemodynamic parameters of pulsatile blood flow is presented in a stenotic artery with non-Newtonian models using ADINA. Blood flow was considered laminar, and the arterial wall was considered rigid. Studied stenosis severities were 30, 50, and 70% of the cross-sectional area of the artery. Six non-Newtonian models were used to model the non-Newtonian behavior of blood, and their results were compared with the Newtonian model. The results showed that in Power-law and Walburn-Schneck models, unlike other models, shear stress values before and after the stenosis were smaller than Newtonian models. Also, in maximum flow rate, the Carreua, generalized Power-law, Casson, and Carreua-Yasuda models showed a reduction in global importance factor of non-Newtonian behavior, and subsequently, the results approached Newtonian model. In minimum flow rate, the global importance factor of Newtonian behavior increased, which highlighted the importance of Newtonian model. In minimum flow rate, Carreua-Yasuda model was more sensitive to the non-Newtonian behavior of blood compared to Carreua, Casson, and Power-law models. Also, in that time period, Walburn-Schneck was less sensitive to the non-Newtonian behavior of blood. On the other hand, this model did not show sensitivity when the flow rate was at its peak. Power-law model overestimated the global importance factor values. Therefore, Power-law model was not suitable, because it showed extreme sensitivity to dimension. Walburn-Schneck model was not suitable too because it lacked sensitivity.
Micro and Nano Systems
Aylar Khooshehmehri; Abdollah Eslami Majd; Elham Arabsheybani
Abstract
The hemispherical resonator gyro (HRG) is a type of precision inertial sensor that has the advantages of direct angle measurement and unlimited dynamic range. The overall accuracy of the HRG is due to the quality of its resonator shell, and improving the performance of resonators requires a proper understanding ...
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The hemispherical resonator gyro (HRG) is a type of precision inertial sensor that has the advantages of direct angle measurement and unlimited dynamic range. The overall accuracy of the HRG is due to the quality of its resonator shell, and improving the performance of resonators requires a proper understanding of the processes of energy damping in each resonance cycle, which has a significant impact on sensor performance. In this paper, in order to investigate the losses in the hemisphere shell resonator, first, the equations governing the shell are studied, and three-dimensional modeling is performed in COMSOL software. By performing mechanical simulations, the resonance modes and the natural frequency of the shell are investigated, and finally, the second and third resonance modes are selected as the optimal operating mode of the gyroscope. Also, by performing thermal simulations, the dominant energy damping processes, such as thermo-elastic damping and anchor loss were analyzed and simulated, and the effect of shell material on damping was investigated. Then the quality factor of the resonator was evaluated based on its geometry and material. In this way, according to the scope of work of the gyroscope, this process can be used to design the specifications of the shell to achieve a resonator with the desired quality factor.
Composite Materials
Hamed Khosravi; Reza Eslami-Farsani
Abstract
This work reports the high-velocity impact response of multiscale anisogrid composite (AGC) panels. The aim of the present study is to evaluate the influence of surface-modified multi-walled carbon nanotubes (S-MWCNTs) at different S-MWCNTs contents (0-0.5 wt.% at an interval of 0.1 wt.%) on the high-velocity ...
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This work reports the high-velocity impact response of multiscale anisogrid composite (AGC) panels. The aim of the present study is to evaluate the influence of surface-modified multi-walled carbon nanotubes (S-MWCNTs) at different S-MWCNTs contents (0-0.5 wt.% at an interval of 0.1 wt.%) on the high-velocity impact responses of E-glass/epoxy AGC. Surface modification of MWCNTs is confirmed by Fourier-transform infrared (FTIR) and thermogravimetric (TGA) analyses. AGC panels were fabricated via a manual filament winding technique. E-glass fiber roving and E-glass woven fabric are employed as reinforcing agents in ribs and skin, respectively. The impact test is done on the composite panels by a cylindrical projectile with a conical nose. The results showe that the highest enhancement in the impact characteristics is attributed to the panel containing 0.4 wt.% S-MWCNTs. Based on the analysis of fracture surfaces, enhanced interfacial fiber/matrix bonding is observed for the S-MWCNTs loaded specimen. Furthermore, the incorporation of MWCNTs leads to the reduced damaged area and enhanced tolerance of damage.
Computational Fluid Dynamics (CFD)
Kandassamy K; B. Prabu
Abstract
Heat dissipation in electronic circuits is important to maintain their reliability and functionality. In this work, microchannel 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, microchannel 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 arrayed heat sinks. 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 4.365 W respectively. The pressure drop of the proposed models is lower than the conventional microchannel arrays.
Robotics
M. Mohammadi; R. Dehghani; A. R. Ahmadi
Abstract
In this paper, a quadrotor with two manipulators constrained on a straight path is modeled and a robust adaptive controller is proposed for it. Adding two manipulators to quadrotor increases its capabilities and applications in industry. Here, these two manipulators are used to place the robot on a constraint ...
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In this paper, a quadrotor with two manipulators constrained on a straight path is modeled and a robust adaptive controller is proposed for it. Adding two manipulators to quadrotor increases its capabilities and applications in industry. Here, these two manipulators are used to place the robot on a constraint path so that the quadrotor can perform monitoring operations more accurately, since the under-actuated quadrotor becomes over-actuated by these constrained manipulators and one can use this feature to accurately control the position of the robot. Reduced form of motion equations is derived for the constrained quadrotor and based on this a robust adaptive controller is proposed. The nonlinear terms in the dynamic model are approximated by basic functions with constant weights; and adaptive laws are designed by projection operator. Stability analysis is performed based on the Lyapunov theory. Evaluation of the presented controller is done by some numerical simulations. The simulation results showed that the robot tracks the reference path with bounded error in spite of dynamic uncertainties and wind force; and satisfies the considered constraints.
Fatigue
J. Amirian; H. Safari; M. Shirani; M. Moradi; S. Shabani
Abstract
Generally, fatigue failure in an element happens at the notch on a surface where the stress level rises because of the stress concentration effect. The present paper investigates the effect of a notch on the fatigue life of the HSLA100 (high strength low alloy) steel which is widely applicable in ...
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Generally, fatigue failure in an element happens at the notch on a surface where the stress level rises because of the stress concentration effect. The present paper investigates the effect of a notch on the fatigue life of the HSLA100 (high strength low alloy) steel which is widely applicable in the marine industry. Tensile test was conducted on specimens and mechanical properties were obtained. Rotating bending and axial fatigue tests were performed at room temperature on smooth and notched specimens and S-N curves were obtained. Using the obtained S-N curve for smooth specimens, the fatigue strength factor for the notched specimens were predicted by Weibull's weakest-link, Peterson, Neuber, stress gradient and critical distance methods and compared with experimental results. It was found that the critical distance and also Weibull’s weakest-link methods have the best agreement with experimental results.
Plates and Shells
Abstract
This paper is concerned with an investigation into the localized instability of a thin elastic orthotropic semi-infinite plate. In this study, a semi-infinite plate, simply supported on two edges and under different boundary conditions of clamped, hinged, sliding contact and free on the other edge, is ...
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This paper is concerned with an investigation into the localized instability of a thin elastic orthotropic semi-infinite plate. In this study, a semi-infinite plate, simply supported on two edges and under different boundary conditions of clamped, hinged, sliding contact and free on the other edge, is studied. A mathematical model is used and a general solution is presented. The conditions under which localized solutions exist are investigated.
Composite Materials
S. Mohammadi*; F. Abdi
Abstract
In the presented work, sulfur concrete and rubber were used for producing functionally graded materials (FGM). The physical and mechanical properties of sulfur concrete and rubber were changed continuously across the thickness. On one side, there was just rubber and, on the other, there was pure sulfur; ...
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In the presented work, sulfur concrete and rubber were used for producing functionally graded materials (FGM). The physical and mechanical properties of sulfur concrete and rubber were changed continuously across the thickness. On one side, there was just rubber and, on the other, there was pure sulfur; the properties of each substance were moved to reach another. This kind of material was constructed by applying mechanical pressure on all layers together and heating in a casting die. Thus, it is essential to consider the quantity of sulfur and rubber at each layer and the rule obeyed by physical and mechanical properties. In the drop test, it was found that the elastic impact coefficient changed from sulfur concrete around 50% to rubber around near zero. It seems that, by changing some parameters like combination percentage or layers' thickness, it is possible to optimize the FGM.
Vibration
Rouhollah Hosseini; Mohsen Hamedi
Abstract
The concept of “energy harvesting” is to design smart systems to capture the ambient energy and to convert it to usable electrical power for supplying small electronics devices and sensors. The goal is to develop autonomous and self-powered devices that do not need any replacement of traditional ...
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The concept of “energy harvesting” is to design smart systems to capture the ambient energy and to convert it to usable electrical power for supplying small electronics devices and sensors. The goal is to develop autonomous and self-powered devices that do not need any replacement of traditional electrochemical batteries. Now piezoelectric cantilever structures are being used to harvest vibration energy for self-powered devices. However, the geometry of a piezoelectric cantilever beam will greatly affect its vibration energy harvesting ability. This paper deduces a remarkably precise analytical formula for calculating the fundamental resonant frequency of bimorph V-shaped cantilevers using Rayleigh method. This analytical formula, which is convenient for mechanical energy harvester design based on Piezoelectric effect, is then validated by ABAQUS simulation. This formula raises a new perspective that, among all the bimorph V-shaped cantilevers and in comparison with rectangular one, the simplest tapered cantilever beam can lead to maximum resonant frequency and highest sensitivity. The derived formula can be commonly used as a relatively precise rule of thumb in such systems.
Welding
Satish Chinchanikar; Vaibhav S. Gaikwad
Abstract
Researchers have worked on many facets of joining of similar/dissimilar aluminum alloys using different joining techniques and came up with their own recommendations. Friction Stir Welding (FSW) is widely preferred for joining aluminum alloys being an economical alternative to produce high-quality welds. ...
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Researchers have worked on many facets of joining of similar/dissimilar aluminum alloys using different joining techniques and came up with their own recommendations. Friction Stir Welding (FSW) is widely preferred for joining aluminum alloys being an economical alternative to produce high-quality welds. However, obtaining high strength welded joints without the detrimental and visible effects still needs attention considering the effect of hybrid FSW techniques, tool material and geometry, process parameters (tool rotation, welding speed, and plunge depth), and post welding treatments. This study presents the state of the art with the authors’ own inferences on the evaluation of FSW performances in terms of joint tensile strength, fatigue strength, corrosion resistance, residual stresses, microstructure, and microhardness. This study also presents attempts made by the researchers on modeling and parametric optimization of FSW to finding scope for application of advanced optimization techniques and development of predictive models for mechanical properties of welded joints. This study emphasizes more studies required on the comparative evaluation of FSW performance with the application of ultrasonic frequency combinedly or individually on advancing and retreating sides of plates.
Forming
Gh. Payganeh; J. Shahbazi Karami; K. Malekzadeh Fard
Abstract
In this paper, single, bi-layered and three-layered tube hydroforming processes were numerically simulated using the finite element method. It was found that the final bulges heights resulted from the models were in good agreement with the experimental results. Three types of modeling were kept with ...
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In this paper, single, bi-layered and three-layered tube hydroforming processes were numerically simulated using the finite element method. It was found that the final bulges heights resulted from the models were in good agreement with the experimental results. Three types of modeling were kept with the same geometry, tube material and process parameters to be compared between the obtained hydroformed products (branch height, thickness reduction and wrinkling) using different loading path types. The results were also discussed.
Vibration
M. M. Soleymani; M. A. Hajabasi; S. Elahi Mahani
Abstract
In this paper, a rectangular sandwich plate with a constrained layer and an electrorheological (ER) fluid core is investigated. The rectangular plate is covered an ER fluid core and a constraining layer to improve the stability of the system. The two outer layers of the sandwich structure are elastic. ...
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In this paper, a rectangular sandwich plate with a constrained layer and an electrorheological (ER) fluid core is investigated. The rectangular plate is covered an ER fluid core and a constraining layer to improve the stability of the system. The two outer layers of the sandwich structure are elastic. The viscoelastic materials express the middle layer behavior under electric field and small strain. Rheological property of an ER material, such as viscosity, plasticity, and elasticity, may be changed when applying an electric field. The ER core is found to have a significant effect on the stability of the sandwich plate. In this paper, based on the displacement field of each layer, the kinetic energy and strain energy are separately obtained for each layer. Transverse displacement of the second layer changes linearly between the transverse displacement of the first and third layers. The loss energy of the second layer consisting of the ER fluid is also calculated and, with the replacement of total kinetic energy, total strain energy, and energy dissipation in the Lagrange's equation, the structural motion equation is obtained. Natural frequencies and loss factor for the electric fields as well as the ratio of different thicknesses calculated are by Navier analytical method. As the applied electric field increases, the natural frequency of the sandwich plate increases and the modal loss factor decreases. With increasing the thickness of the ER layer, the natural frequencies of the sandwich plate are decreased. Thickness of the constrained layer also affects the stability of the sandwich plate.
Forming
Mohammad Honarpisheh; Ahmad Gheysarian
Abstract
Single point incremental sheet metal forming is a sheet metal forming process that forms products without the complex dies and tools with low cost. In this study, the incremental sheet metal forming process has been experimentally investigated on the explosively-welded Al/Cu bimetal sheets. Also, the ...
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Single point incremental sheet metal forming is a sheet metal forming process that forms products without the complex dies and tools with low cost. In this study, the incremental sheet metal forming process has been experimentally investigated on the explosively-welded Al/Cu bimetal sheets. Also, the effects of process parameters, such as arrangement of layer`s bimetal, tool diameter and tool path were investigated on the forming force, thickness distribution, formability and roughness. At first, the bimetals were produced by explosive welding process. Then, two tool diameters, step and spiral tool paths and layer arrangement were chosen as input parameters. The results showed that the forming force increases with increasing the tool diameter and using aluminum as a top layer (contact with tool). Also, using spiral tool path increases the average forming force and decreases the maximum thickness changing. The formability increases with increasing the tool diameter and using the copper as top layer with spiral tool path.
Fluid Mechanics
S. F. Ahmed
Abstract
Energy equation for turbulent flow in a rotating system was derived in terms of second order correlation tensors, where the correlation tensors were functions of space coordinates, distance between two points and time. To reveal the relationship of turbulent energy between two points, one point was taken ...
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Energy equation for turbulent flow in a rotating system was derived in terms of second order correlation tensors, where the correlation tensors were functions of space coordinates, distance between two points and time. To reveal the relationship of turbulent energy between two points, one point was taken as origin of the coordinate system. Due to rotation, the Coriolis force played an important role in the rotating system of turbulent flow. The correlation between pressure fluctuations and velocity fluctuations at the two points of flow field was applied to the turbulent energy equation, in which the Coriolis force and centrifugal force acted on the fluid.
Computational Fluid Dynamics (CFD)
Muhim Chutia
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.
Energy Systems
Mohammed Ridha Jawad Al-Tameemi; Samir Yahya; Saadoon Abdul Hafedh; Itimad D. J. AZZAWI
Abstract
A thermodynamic evaluation is conducted on a combined heat and power system integrating a gas turbine (GT), a heat exchanger (HX1), and an organic Rankine cycle (ORC). Traditionally, ORC bottoming GT cycle is limited to mechanical power production. The novelty of this study is to recover wasted heat ...
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A thermodynamic evaluation is conducted on a combined heat and power system integrating a gas turbine (GT), a heat exchanger (HX1), and an organic Rankine cycle (ORC). Traditionally, ORC bottoming GT cycle is limited to mechanical power production. The novelty of this study is to recover wasted heat from the GT cycle in multistage, which is used for the simultaneous production of mechanical power and hot water supply. In the first stage, the HX1 recovers heat from the GT cycle compressed air to heat the water stream. In the second stage, the ORC cycle recovers thermal energy from the GT turbine exhaust stream to produce extra mechanical power with the remaining latent heat used to heat the water. Two models are proposed for comparison using ASPEN Plus software linked with the RAFPROP database. The modelled GT, in this study, is adopted from an actual machine. The steady-state results show that the combined system achieves 51.55% thermal efficiency compared with a standalone GT efficiency, which is only 21%. The thermal efficiency is divided into 24% mechanical power and 27.55% thermal load. The output hot water temperature is 65 oC. The outcomes of increasing the GT pressure ratio (12-25) are higher combined cycle net power output by up to 16% with a 9.5% reduction in the thermal energy rejected to the environment. Also, the GT efficiency increases from 20% to 22.5%; however, the final water temperature declines from 67 oC to 60 oC, which is still appropriate for various heating applications.
Energy Science and Technology
Jamasb Pirkandi; Amirali Amiralaei; Mohammad Omian
Abstract
In this research, a combined cooling, heating and power system (CCHP) has been analyzed from the perspective of entropy and exergy. The primary driver and the cooling system for this combined system consist of a micro gas turbine and a hot water lithium bromide single-effect absorption chiller, respectively. ...
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In this research, a combined cooling, heating and power system (CCHP) has been analyzed from the perspective of entropy and exergy. The primary driver and the cooling system for this combined system consist of a micro gas turbine and a hot water lithium bromide single-effect absorption chiller, respectively. The effects of compressor pressure ratio, micro turbine inlet gas temperature and chiller cooling capacity on important system efficiencies and other operational parameters (e.g., electrical efficiency, thermal efficiency, combined heating and power cogeneration efficiency, and combined cooling, heating and power cogeneration efficiency) have been investigated. The findings indicate that the system has its highest electrical efficiency at a compressor pressure ratio of 5. Also at this pressure ratio, the cogeneration efficiency (combined heating, cooling and power) and the exergy efficiency are about 48% and 24%, respectively. Moreover, the increase of the turbine inlet gas temperature has had a positive effect on the investigated parameters. The results show that the increase of cooling capacity reduces the cogeneration efficiencies, but has no effect on the exergy efficiency. Also, by considering specific values for the studied parameters, the amounts of generated entropy and destroyed exergy in various parts of the system have been calculated. The results indicate that the highest amounts of entropy and exergy have been generated and destroyed in the combustion chamber. Parts of the results indicate a system state in which the overall efficiency (combined heating, cooling and power cogeneration efficiency) of the system has increased 13% relative to the system’s initial state.
Heat and Mass Transfer
P. Sreenivasulu; B. Vasu; T. Poornima; N. Bhaskar Reddy
Abstract
The present paper focuses on numerical study for an inclined magneto-hydrodynamic effect on free convection flow of a tangent hyperbolic nanofluid embedded with Carbon nanotubes (CNTs) over a stretching surface taking velocity and thermal slip into account. Two types of nanoparticles are considered for ...
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The present paper focuses on numerical study for an inclined magneto-hydrodynamic effect on free convection flow of a tangent hyperbolic nanofluid embedded with Carbon nanotubes (CNTs) over a stretching surface taking velocity and thermal slip into account. Two types of nanoparticles are considered for the study; they are single and multi-walled nanotubes. The presentation of single-parameter group (Lie group) transformations reduces the independent variable number by one, and hence the partial differential governing equations with the supplementary atmospheres into an ordinary differential equation with the appropriate suitable conditions. The obtained ordinary differential equations are then numerically solved by employing fourth order Runge-Kutta technique along with shooting method. The effects of the various parameters governing the flow field are presented with the help of graphs. The investigation reveals that the non-Newtonian MWWCNTs Tangent hyperbolic nano-liquid reduces the friction near the stretching sheet contrasting SWCNTs. This combination can be used as a friction lessening agent/factor. Usage of CNTs shows an excellent performance in enhancing the thermal conductivity of the nanoliquid and single wall carbon nanotubes (SWCNTs) has higher thermal conductivity than multi wall carbon nanotubes (MWCNTs) even in the presence of radiative heat transfer and heat source. Comparison with existing results available in literature is made and had an excellent coincidence with our numerical method.
Heat and Mass Transfer
M. Rahimi; M. Mortazaei
Abstract
Jet impingement heat transfer is an effective and practical approach that is employed in many industrial processes where heating, cooling, or drying is required. Details of the heat or mass transfer rate have been investigated both experimentally and numerically and can be found in the published literature. ...
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Jet impingement heat transfer is an effective and practical approach that is employed in many industrial processes where heating, cooling, or drying is required. Details of the heat or mass transfer rate have been investigated both experimentally and numerically and can be found in the published literature. In most of the numerical studies, control-volume approach has been employed to solve the governing equations of the thermal and flow fields. Using this numerical approach, a pressure correction equation is usually developed from the conservation equations in a rigorous manner to obtain the pressure distribution. Avoiding the complexities encountered in the traditional manner, a full implicit finite-difference method was developed for the first time and applied for studying jet impingement heat transfer. Similar to the velocity components, static pressure was also treated as an unknown variable in this approach. Specifications of both flow and thermal fields were obtained for two cases of confined and unconfined jets by the proposed numerical method. It was demonstrated that this novel numerical approach was a straightforward method, which required no additional equation for pressure calculation, and had the potential use in other two- or three-dimensional flow and thermal field analysis.
Fluid Mechanics
Kvenu Reddy; M. Gnaneswara Reddy
Abstract
In this paper, we analyze the thermal radiation and chemical reaction impacts on MHD peristaltic motion of the Eyring-Powell fluid through a porous medium in a channel with compliant walls under slip conditions for velocity, temperature, and concentration. Assumptions of a long wave length and low Reynolds ...
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In this paper, we analyze the thermal radiation and chemical reaction impacts on MHD peristaltic motion of the Eyring-Powell fluid through a porous medium in a channel with compliant walls under slip conditions for velocity, temperature, and concentration. Assumptions of a long wave length and low Reynolds number are considered. The modeled equations are computed by using the perturbation method. The resulting non-linear system is solved for the stream function, velocity, temperature, concentration, skin-friction coefficient, heat transfer coefficient and mass transfer coefficient. The flow quantities are examined for various parameters. Temperature depresses with an enhancee in the radiation parameter, while the opposite effect is observed for the concentration. The fluid concentration enhances and depresses with generative and destructive chemical reaction respectively. The trapped bolus whose size diminishes as the Powel-Eyring parameter increases while it enhances as another Powell fluid parameter increases. The trapped bolus whose size rises when Darcy number enhances.
Computational Fluid Dynamics (CFD)
S. Akbarnejad; M. Ziabasharhagh
Abstract
This paper presents a novel 1D modeling approach to optimize steam ejector entrainment ratios, introducing new definitions of ejector efficiency and enhancement methods. Using the proposed model, an ejector is tailored for specific boundary conditions with available computational fluid mechanic ...
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This paper presents a novel 1D modeling approach to optimize steam ejector entrainment ratios, introducing new definitions of ejector efficiency and enhancement methods. Using the proposed model, an ejector is tailored for specific boundary conditions with available computational fluid mechanic results for validation. Dimensional and geometrical parameters are computed from the theoretical 1D model, and various geometries are explored using computational fluid mechanic to determine entrainment ratios. Innovative definitions of ejector efficiency are introduced. The first definition compares the entrainment ratio of the ejector to a system comprising a steam compressor, turbine, and mixer, yielding an efficiency of 13.5% under specified conditions. The second, more practical definition calculates the maximum achievable entrainment ratio, disregarding frictional losses, resulting in an efficiency of 70%. An algorithm is proposed to optimize ejector dimensions to approach this maximum. Using this algorithm, the optimum throat diameter was determined through computational fluid mechanic analysis, demonstrating an increase in the entrainment ratio from 0.7 to 1.25. The theoretical maximum value calculated by the 1D model is 1.282, indicating that 97.7% of the theoretical maximum was achieved in computational fluid mechanic simulations. This highlights the significant improvement in the entrainment ratio using the 1D model and delineates its limit under given conditions. The third definition establishes the theoretical maximum entrainment ratio given specific boundary conditions and dimensions, assuming no losses in the nozzle, mixing process, or diffuser; yielding an efficiency of 81% for the same ejector studied.
Fluid Mechanics
S. M. S. M. Hosseinalipour; A. Tohidi; M. Shokrpour
Abstract
The motivation for this work is to propose a first thorough review of dough rheological models used in numerical applications. Although many models have been developed to describe dough rheological characteristics, few of them are employed by researchers in numerical applications. This article reviews ...
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The motivation for this work is to propose a first thorough review of dough rheological models used in numerical applications. Although many models have been developed to describe dough rheological characteristics, few of them are employed by researchers in numerical applications. This article reviews them in detail and attempts to provide new insight into the use of dough rheological models.
