Mir Elyad Vakhshouri; Burhan ÇUhadaroğlu
Abstract
The effects of uniform injection and suction through the surfaces of a perforated square cylinder on the vortex shedding, heat transfer and some aerodynamic parameters have been investigated numerically. The finite-volume method has been used for solving the Navier-Stokes equations for incompressible ...
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The effects of uniform injection and suction through the surfaces of a perforated square cylinder on the vortex shedding, heat transfer and some aerodynamic parameters have been investigated numerically. The finite-volume method has been used for solving the Navier-Stokes equations for incompressible and turbulent near-wake flow ( ) with the k-ɛ turbulence model equations. To find the optimum conditions, the effects of injection and suction through the front surface (case Ⅰ), the rear surface (case Ⅱ), top-bottom surfaces (case Ⅲ) and all surfaces (case Ⅳ) with various injection/suction coefficient G are studied. The results reveal that parameters such as pressure and drag coefficients and Nusselt number are influenced drastically in some cases as well as flow field parameters. For instance, the maximum reduction of the drag coefficient occurs at case Ⅳ while the maximum increase and reduction of Nu number occur at for all cases about 46% and 32%, 61% and 63%, 92% and 60% and 180% and 115% for cases Ⅰ, Ⅱ, Ⅲ and Ⅳ respectively.
Finite Elements Method (FEM)
Zuliang Lu*
Abstract
In this paper, a positive definite semi-discrete mixed finite element method was presented for two-dimensional parabolic equations. In the new positive definite systems, the gradient equation and flux equations were separated from their scalar unknown equations. Also, the existence and uniqueness ...
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In this paper, a positive definite semi-discrete mixed finite element method was presented for two-dimensional parabolic equations. In the new positive definite systems, the gradient equation and flux equations were separated from their scalar unknown equations. Also, the existence and uniqueness of the semi-discrete mixed finite element solutions were proven. Error estimates were also obtained for the semi-discrete schemes.Finally, a numerical example was presented to show theoretical results.
Vibration
H. M. Panahiha; A. Davar
Abstract
In this paper, the nonlinear free vibrations of thin symmetric and non-symmetric cross-ply composite plates subjected to biaxial initial stresses are investigated. Because of their excellent properties such as specific strength and specific stiffness, composite plates have wide applications in aerospace ...
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In this paper, the nonlinear free vibrations of thin symmetric and non-symmetric cross-ply composite plates subjected to biaxial initial stresses are investigated. Because of their excellent properties such as specific strength and specific stiffness, composite plates have wide applications in aerospace and mechanical structures. Based on Von-Karman's strain-displacement relations and using Galerkin method, the nonlinear differential equation of free vibrations of initially stressed composite plate is obtained. This nonlinear equation is solved using two different analytical perturbation methods, namely method of multiple scales (MTS) and homotopy perturbation method (HPM), to analyze the nonlinear vibrations of initially stressed cross-ply composite plates. Effects of tensile and compressive biaxial initial stresses, initial vibration amplitude, thickness, and aspect ratios of the composite plates on the frequency behavior are investigated. The validity of the results is confirmed by making a comparison with those reported in the literature. According to the results, both analytical solutions show increasing trends for natural frequency parameters by increasing normal initial stresses. Regardless of the value of initial biaxial stresses, for both symmetric and non-symmetric plates, the results of MTS and HPM are in close agreement for the smallest initial amplitude. However, for compressive initial stresses, by increasing initial amplitude ratios, the discrepancies between the results of HPM and MTS increase for symmetric and non-symmetric plates. Although HPM includes less computational effort (smaller length of formulation) than MTS, the linear-to-nonlinear frequency ratios obtained using MTS method become closer to those obtained by HPM as initial vibration amplitude is decreased and initial stress is increased.
Fluid Mechanics
Prasannakumara B.C; Shashikumar N.S; Archana M
Abstract
The steady three-dimensional boundary layer flow and heat transfer of a dusty fluid towards a stretching sheet with convective boundary conditions is investigated by using similarity solution approach. The free stream along z-direction impinges on the stretching sheet to produce a flow with different ...
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The steady three-dimensional boundary layer flow and heat transfer of a dusty fluid towards a stretching sheet with convective boundary conditions is investigated by using similarity solution approach. The free stream along z-direction impinges on the stretching sheet to produce a flow with different velocity components. The governing equations are reduced into ordinary differential equations by using appropriate similarity variables. Reduced nonlinear ordinary differential equations subjected to the associated boundary conditions are solved numerically by using Runge–Kutta fourth-fifth order method along with Shooting technique. The effects of the physical parameters like magnetic parameter, velocity ratio, fluid and thermal particle interaction parameter, Prandtl number, Eckert number and Biot number on flow and heat characteristics are examined, illustrated graphically, and discussed in detail. The results indicate that the fluid phase velocity is always greater than that of the particle phase and temperature profiles of fluid and dust phases increases with the increase of the Eckert number.
Manufacturing Processes
I. Shivakoti; G. Kibria; S. Diyaley; B. B. Pradhan
Abstract
Correct selection of manufacturing condition is one of the most important aspects which should be considered in the majority of manufacturing processes, particularly in the process related to advanced machining process like electrical discharge machining. In electrical discharge machining (EDM), ...
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Correct selection of manufacturing condition is one of the most important aspects which should be considered in the majority of manufacturing processes, particularly in the process related to advanced machining process like electrical discharge machining. In electrical discharge machining (EDM), dielectric fluid plays an important role since machining characteristics are greatly influenced by the nature or characteristics of employed dielectric. Moreover, adding various types of abrasives or salt in the fluid at different concentrations also affect the machining performance because of changing dielectric strength property. The present paper addressed the influence of NaNO3 mixed de-ionized water as a dielectric fluid on micro-hole machining performance criteria such as material removal rate (MRR), tool wear rate (TWR), overcut (OC) and taper during machining of D3 die steel plate.
Control
Zuliang Lu*
Abstract
The aim of this work is to investigate the variational discretization and mixed finite element methods for optimal control problem governed by semi linear parabolic equations with integral constraint. The state and co-state are approximated by the lowest order Raviart-Thomas mixed finite element spaces ...
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The aim of this work is to investigate the variational discretization and mixed finite element methods for optimal control problem governed by semi linear parabolic equations with integral constraint. The state and co-state are approximated by the lowest order Raviart-Thomas mixed finite element spaces and the control is not discreted. Optimal error estimates in L2 are established for the state and the control variable. As a result, it can be proved that the discrete solutions possess the convergence property of order. Finally, a numerical example is presented which confirms the theoretical results.
Energy Science and Technology
Ahmed F Hasan; Salah N Farhan
Abstract
Phase change materials have attracted a considerable attention in thermal energy storage research recently due to their thermal characteristic. Composite materials have great potential as one of the best alternative approach that would be utilized to increase the thermal performance of this sort of materials. ...
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Phase change materials have attracted a considerable attention in thermal energy storage research recently due to their thermal characteristic. Composite materials have great potential as one of the best alternative approach that would be utilized to increase the thermal performance of this sort of materials. This work aims to improve the Latent Heat energy Storage Unit (LHSU) in terms of thermal performance during the melting process by utilizing honeycomb metal structures configuration. An experimental study has been carried out to examine the thermal behavior of this particular material in honeycomb LHSU. The thermal performance evaluation in terms of melting time of the proposed honeycomb LHSU was conducted in comparison with the normal LHSU. The influences of using different heat transfer fluid temperature on the charging power are considered for the enhanced geometrical configuration. The results showed significant enhancement in the melting time which reached 87%. Also, the melting range in the lower part of the storage unit was improved compared with the normal one from 190 to 24 min in case of using honeycomb. For the propose of configuration, by increasing the fluid temperature, charging power was accelerated, which in turn reduces the charging time from 14% to 16.
Computational Fluid Dynamics (CFD)
S. Harimi; Azam Marjani
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.
Heat and Mass Transfer
Pooja Sharma; Tarun Sharma; Navin Kumar
Abstract
Entropy generation due to viscous incompressible MHD forced convective dissipative fluid flow through a horizontal channel of finite depth in the existence of an inclined magnetic field and heat source effect has been examined. The governing non-linear partial differential equations for momentum, energy ...
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Entropy generation due to viscous incompressible MHD forced convective dissipative fluid flow through a horizontal channel of finite depth in the existence of an inclined magnetic field and heat source effect has been examined. The governing non-linear partial differential equations for momentum, energy and entropy generation are derived and solved by using the analytical method. In addition; the skin friction coefficient and Nusselt number are calculated numerically and their values are presented through the tables for the upper and the bottom wall of the channel. It was concluded that; total entropy generation rate and Bejan number are reduced due to rise in the inclination angle of the magnetic field. Also, an increment in the heat source prop ups the fluid temperature and total entropy generation rate. This study will help to reduce the energy loss due to reversible process and heat dissipation. The results are very useful for chemical and metallurgy industries.
Fracture Mechanics
M. Shariati; A. M. Majd Sabeti; H. Gharooni
Abstract
Existence of cracks in industrial structures is one of the important causes of their failure, especially when they are subjected to important axial compressive forces that might lead to buckling. Therefore, it must be considered in stress analysis and designing and loading of such structures. In this ...
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Existence of cracks in industrial structures is one of the important causes of their failure, especially when they are subjected to important axial compressive forces that might lead to buckling. Therefore, it must be considered in stress analysis and designing and loading of such structures. In this paper, the buckling and post-buckling behaviors of stainless-steel cracked plates under axial compression load were investigated both experimentally and numerically and effects of the geometrical and mechanical parameters, such as crack length, crack angle, crack position, plate imperfection, load band, and plate thickness on the critical buckling load were studied. In the experimental study, mechanical properties and plastic behavior of stainless steel plates were determined for the subsequent numerical study. Numerical modeling was carried out by ABAQUS finite element software. Numerical predictions were compared with the experimental results and the reliability of the numerical solution was proven. Results demonstrated the considerable effects of the mentioned parameters on the critical buckling load of plate.
Fluid Mechanics
Aminreza Noghrehabadia; Mohammad Ghalambaza; Afshin Ghanbarzadeh
Abstract
In this paper, a monotone positive solution is studied for buckling of a distributed model of multi walled carbon nanotube (MWCNT) cantilevers in the vicinity of thin and thick graphite sheets subject to intermolecular forces. In the modeling of intermolecular forces, Van der Waals forces are taken into ...
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In this paper, a monotone positive solution is studied for buckling of a distributed model of multi walled carbon nanotube (MWCNT) cantilevers in the vicinity of thin and thick graphite sheets subject to intermolecular forces. In the modeling of intermolecular forces, Van der Waals forces are taken into account. A hybrid nano-scale continuum model based on Lennard–Jones potential is applied to simulate the intermolecular force-induced deflection of MWCNT. A positive monotone solution based on Green’s function in the form of a nonlinear iterative integral is introduced to obtain a solution for deflection of MWCNT cantilevers. In order to determine the accuracy of the presented method, the results are compared with numerical results of a numerical method as well as other methods reported in the literature. The results show that the monotone iterative solution is stable and converged to numerical results with a few iterations. The results of the present work are useful to prove the stability and convergence of Green’s function to deal with deflection of nano cantilever actuators in future works and simplifications.
Manufacturing Processes
Mahdi Ghamami; Masoud Shariat Panahi; Maryam Rezaei
Abstract
In today's design, system complexity and increasing demand for safer, more efficient and less costly systems have created new challenges in science and engineering. Locomotives are products which are designed according to market order and technical needs of customers. Accordingly, targets of companies, ...
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In today's design, system complexity and increasing demand for safer, more efficient and less costly systems have created new challenges in science and engineering. Locomotives are products which are designed according to market order and technical needs of customers. Accordingly, targets of companies, especially designers and manufacturers of locomotives, have always been on the path of progress and seek to offer products with higher technology than other competitors. Quality of body structures is based on indicators such as natural frequency, displacement, fatigue life and maximum stress. Natural frequency of various components of the system and their adaption to each other are important for avoiding the phenomenon of resonance. In this study, body structures of ER24 locomotive (Iran Safir Locomotive) was studied. A combination of imperialist competitive algorithm (ICA) and artificial neural network was proposed to find optimal weight of structures while natural frequencies were in the determined range. Optimization of locomotive's structure was performed with an emphasis on maintaining locomotive abilities in static and dynamic fields. The results indicated that use of optimization techniques in the design process was a powerful and effective tool for identifying and improving main dynamic characteristics of structures and also optimizing performance in stress, noise and vibration fields.
Heat and Mass Transfer
J. Prakash; P. Durga Prasad; R. V. M. S. S. Kiran Kumar; S. V. K. Varma
Abstract
The main purpose of this work is to investigate the porous medium and diffusion-thermo effects on unsteady combined convection magneto hydrodynamics boundary layer flow of viscous electrically conducting fluid over a vertical permeable surface embedded in a high porous medium, in the presence of first ...
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The main purpose of this work is to investigate the porous medium and diffusion-thermo effects on unsteady combined convection magneto hydrodynamics boundary layer flow of viscous electrically conducting fluid over a vertical permeable surface embedded in a high porous medium, in the presence of first order chemical reaction and thermal radiation. The slip boundary condition is applied at the porous interface. A uniform Magnetic field is applied normal to the direction of the fluid flow. The non-linear coupled partial differential equation are solved by perturbation method and obtained the expressions for concentration, temperature and velocity fields. The rate of mass transfer in terms of Sherwood number , the rate of heat transfer in terms of Nusselt number and the Skin friction coefficient are also derived. The Profiles of fluid flow quantities for various values of physical parameters are presented and analyzed. Profiles of fluid flow quantities for various values of physical parameters are presented and analyzed.
Heat and Mass Transfer
S. Mohammed Ibrahim; K. Suneetha
Abstract
The present paper was aimed to study the effects of variable thermal conductivity and heat generation on the flow of a viscous incompressible electrically conducting fluid in the presence of a uniform transverse magnetic field, thermal radiation, porous medium, mass transfer, and variable free stream ...
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The present paper was aimed to study the effects of variable thermal conductivity and heat generation on the flow of a viscous incompressible electrically conducting fluid in the presence of a uniform transverse magnetic field, thermal radiation, porous medium, mass transfer, and variable free stream near a stagnation point on a non-conducting stretching sheet. Equations of continuity, momentum, energy, and mass were transformed into ordinary differential equations and solved numerically using shooting method. Velocity, temperature, and concentration distributions were numerically discussed and presented in the graphs. Skin-friction coefficient, the Nusselt number, and Sherwood number on the sheet were derived and discussed numerically. Their numerical values for various values of physical parameters were presented in the tables. It was found that temperature increased with increasing radiation parameter, R, and concentration decreased with increasing the Schmidt number, Sc. The numerical predications were compared with the existing information in the literature and a good agreement was obtained.
Mechatronics
Zulfiqar Ali Soomro
Abstract
Lateral velocity has very backbone position in the railway vehicle wheelset dynamics as it usually becomes cause of derailment by sliding due to insufficient adhesion ratio. This impropriate balance is pretext owing to contamination and weather procures the disturbances. This perturbation makes hindrances ...
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Lateral velocity has very backbone position in the railway vehicle wheelset dynamics as it usually becomes cause of derailment by sliding due to insufficient adhesion ratio. This impropriate balance is pretext owing to contamination and weather procures the disturbances. This perturbation makes hindrances in proper running of wheelset on track. To analyze the noise, Kalman filter is used based upon the railway dynamic modeling to estimate the actual signals to control the noise by measurement. Thus error percentage is also computed to detect the slippage by adhesion on applicable analysis of creep co-efficient. The motion and velocity of Lateral and yaw analysis for railway vehicle wheelset is of great importance for the slip and sliding point of view. As usually hit has been observed that fatal accidents, destruction of railway vehicle with railway tracks and damage of costly lives happen due to improper control on the lateral and yaw railway dynamic system with chaos management as well as technical point of view. Since controllable estimated lateral velocity assures minimum wheel slide.
Computational Fluid Dynamics (CFD)
Ghanbarali Sheikhzadeh; Mahdi Mollamahdi; Mahmoud Abbaszadeh
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.
Computational Fluid Dynamics (CFD)
Devesh Kumar Baghel; Sobha Lata Sinha; Satish Kumar Dewangan
Abstract
Neonatal incubators provide an artificial thermal environment to maintain the thermoregulation of premature babies. Several studies revealed the dry and latent heat exchange estimation between the newborn's body and the surrounding environment. Heat ...
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Neonatal incubators provide an artificial thermal environment to maintain the thermoregulation of premature babies. Several studies revealed the dry and latent heat exchange estimation between the newborn's body and the surrounding environment. Heat transfer due to convection is leading over the thermal radiation in incubators. The aim of this article is to study the airflow modeling and heat transfer coefficient over an infant’s body inside the incubator. For this purpose, an experiment and a numerical simulation are carried out to develop the methodology, and subsequently computational fluid dynamics (CFD) analysis is accomplished to evaluate the heat transfer coefficient of a preterm infant. By means of the shear stress transport (SST K-ω) turbulence model, 3-D computational, models are numerically studied using the commercial CFD tool Star CCM+. Flow visualization reveals that a large-scale flow circulation pattern is produced in the mean region of the enclosed chamber, and small-scale eddies are generated at corners and close to the walls. The numerical results obtained for heat transfer assessment in the present study are validated with experimental and numerical results available in biomedical open literature.
Manufacturing Processes
Elhachemi Bahloul
Abstract
In contour milling, to render the machining process more automated with significant productivity without remaining material after machining, a new recovery coefficient was developed. The coefficient was inserted in the computation of contour parallel tool paths to fix the radial depth of cut in the way ...
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In contour milling, to render the machining process more automated with significant productivity without remaining material after machining, a new recovery coefficient was developed. The coefficient was inserted in the computation of contour parallel tool paths to fix the radial depth of cut in the way to ensure an optimized overlap area between the passes in the corners, without residuals. Thus, this parameter, which has been earlier inserted by the user, is now being independent and is implemented automatically from the input data of the contour shape of the pocket. In order to prove the effectiveness of the present approach, a detailed comparison with the classical methods found in the literature we also performed. The results clearly show that the new method removes the residuals efficiently in an automatic way and minimizes the toolpath length respect to the other methods. Furthermore, this proposed approach can easily be worked on the actual machine tool.
A. Mahamani; S. Jawahar; J. P. Davim
Abstract
In-situ composites have gained the attention of worldwide researchers in the interest of their greater mechanical properties at the lower reinforcement ratio. Controlling the surface quality of components is a paramount task in the grinding process in order to withstand the creep and fatigue load at ...
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In-situ composites have gained the attention of worldwide researchers in the interest of their greater mechanical properties at the lower reinforcement ratio. Controlling the surface quality of components is a paramount task in the grinding process in order to withstand the creep and fatigue load at service conditions. The current effort is intended to examine the mechanism of surface generation in grinding AA6061-TiB2/ZrB2 in-situ composite under different reinforcement ratios, grinding parameters, and wheel materials. The analysis of results indicates that the grinding of the unreinforced alloy is complicated than the composites. Diamond wheel yields superior performance by generating lesser surface roughness and subsurface hardness at all grinding conditions. Among the various grinding parameters, grinding speed and grinding depth are more sensitive than other parameters. This experimental investigation helps to control the surface roughness and subsurface at various grinding conditions.
Heat and Mass Transfer
Ravi Kumar; D. Vijaya Sekhar; Sk. Abzal
Abstract
Theoretical investigation of Ohmic heating (Joule heating) and radiation on MHD Jeffery fluid model with porous material along the tapered channel with peristalsis is the focus of this study. Long wavelength and low-Reynolds number approximations are used in the mathematical modelling. Axial rate, pressure ...
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Theoretical investigation of Ohmic heating (Joule heating) and radiation on MHD Jeffery fluid model with porous material along the tapered channel with peristalsis is the focus of this study. Long wavelength and low-Reynolds number approximations are used in the mathematical modelling. Axial rate, pressure gradient, temperature, and heat transfer coefficient rate expressions are calculated. Plotting diagrams were used to analyse the impact of physical parameters on flow characteristics, which were then addressed in greater depth. It is worth noting that raising the gravitational parameter, Jeffery fluid parameter, Hartmann number and Porosity parameter raises the fluid’s velocity. Also, as the Ohmic heating (Jeffery fluid) parameter and porosity parameter increase, the axial pressure gradient drop;, and the temperature of the fluid rises. The rate of heatt transfer coefficient rises in region with an increase in the Radiation parameter, Heat generator parameter and Jeffery fluid parameter. Mathematica software is employed to seek out numerical results.
Heat and Mass Transfer
seyed mostafa moafi madani; Javad Alinejad; yasser rostamiyan; keivan fallah
Abstract
In the present study, the effect of the heating pipe profile on natural convection in a two –phase fluid inside a cavity have been investigated. This geometries has been simulated with the Lattice Boltzmann Method based on D2Q9 model for analyzing stream lines, dimensionless velocity field of fluid ...
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In the present study, the effect of the heating pipe profile on natural convection in a two –phase fluid inside a cavity have been investigated. This geometries has been simulated with the Lattice Boltzmann Method based on D2Q9 model for analyzing stream lines, dimensionless velocity field of fluid flow, solid particles volume fraction, temperature arrangement and Nusselt number. Theseparameters have been investigated in 3 cases of the cavity. The results signified by changing the geometry from a horizontal ellipse to a circular one and a vertical ellipse, the Maximum volume fraction of solid particles decreased. Also, by changing the geometry from a horizontal ellipse to a circular and vertical ellipse, larger velocity vectors have been formed around the geometry. The Nusselt number variations of circular and vertical ellipse geometries in the lower half have a similar behavior. The Nusselt number variation of horizontal ellipse geometry in the lower half is insignificant. Also, the Nusselt number of the circular geometry in the upper half is larger and uniform compared to the other two geometries. The highest average Nusselt number belongs to circular, vertical and horizontal ellipse geometries respectively.
Composite Materials
A. Niknami; M. Shariyat
Abstract
In the present research, in contrast to the available papers, not only the superelasticity but also the shape memory effects are taken into account in determination of the impact responses. At the same time, in addition to modifying Brinson’s model for the shape memory alloys (SMAs), to include ...
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In the present research, in contrast to the available papers, not only the superelasticity but also the shape memory effects are taken into account in determination of the impact responses. At the same time, in addition to modifying Brinson’s model for the shape memory alloys (SMAs), to include new parameters and loading events, and Hertz contact law, distributions of the SMA phases are considered to be both localized and time-dependent. Furthermore, effects of the impact-induced heat generation and mechanical energy on the resulting histories of the martensite phase volume fraction, stress-strain, temperature, lateral deflection, and contact force are investigated. The generated heat in the SMA wires during the impact is determined through using a Helmholtz free energy function including the latent heat of the phase transformation. The resulting governing equations are solved by the finite element method. The nonlinear refined constitutive laws are solved through a return-mapping Newton-Raphson procedure. Results reveal that incorporation of the heat generation effects is significant in medium/high-velocity impacts or when the stress field is almost uniform.
Hydraulic and Pneumatic Systems
M. Maghroory; A. Farhadi; P. Naderi
Abstract
To maintain the stability trajectory of vehicles under critical driving conditions, anti lock-anti skid controllers, consisting of four anti-lock sub-controllers for each wheel and two anti-skid sub-controllers for left and right pair wheels have been separately designed. Wheel and body systems have ...
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To maintain the stability trajectory of vehicles under critical driving conditions, anti lock-anti skid controllers, consisting of four anti-lock sub-controllers for each wheel and two anti-skid sub-controllers for left and right pair wheels have been separately designed. Wheel and body systems have been simulated with seven degrees of freedom to evaluate the proper functioning of controllers. Anti-lock controllers control brake torque through persistent monitoring of wheels velocity and acceleration and prevent them from locking up by cutting and releasing the brake fluid flow into wheel brake cylinder. On the other hand, anti-skid controllers have been designed in order to maintain the vehicle along a stable trajectory, calculated from the stable spin theory, and to monitor the vehicle’s trajectory during braking. This controller maintains the vehicle along the desirable trajectory by monitoring vehicle yaw angle and comparing it with the reference yaw angle, and also by adjusting the level of brake fluid input into each wheel’s caliper, and subsequently by adjusting brake torque. At the end of the current research, the use of yaw rate control input in place of yaw angle control input in anti-skid controllers has been suggested through a comparative analysis.
Manufacturing Processes
Ghader Faraji*; Mahmoud Mosavi Mashhadi; Karen Abrinia
Abstract
The current study conducted a finite element (FE) and experimental investigation on tubular channel angular pressing as a noble severe plastic deformation technique for producing ultrafine grained and nanostructure tubular components. To examine the effects of the TCAP process on the strain distribution ...
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The current study conducted a finite element (FE) and experimental investigation on tubular channel angular pressing as a noble severe plastic deformation technique for producing ultrafine grained and nanostructure tubular components. To examine the effects of the TCAP process on the strain distribution and deformation behavior, FE simulations were employed. The FE results demonstrated that equivalent plastic strain of 2.1-2.9 was developed after applying one pass TCAP. Analytical investigations were carried out to calculate the accumulated strain during the process. Tube thinning in the early stages of the process was observed as a result of tensile circumferential strains but this could be compensated for by the back pressure effect resulting from the next shear zones and also compressive circumferential strain resulting from decreasing the tube diameter. Microstructural observations showed significant grain refinement after one pass TCAP on AZ91 magnesium alloy at 300 ºC. Microhardness measurements demonstrated increasing hardness to 78 HV from the initial value of 51 HV.
Thermodynamics and Cumbustion
A. H. Kakaee; J. Zareei
Abstract
Engine performance depends on two main factors of engine speed and ignition time. Ignition timing can affect engine life, fuel economy and engine power. In this paper, to study engine performance of Peugeot 206 TU3A with comparison ratio of 10.5:1 and displacement of 1361CC in MATLAB software, a two-zone ...
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Engine performance depends on two main factors of engine speed and ignition time. Ignition timing can affect engine life, fuel economy and engine power. In this paper, to study engine performance of Peugeot 206 TU3A with comparison ratio of 10.5:1 and displacement of 1361CC in MATLAB software, a two-zone burned/unburned model with the fuel burning rate described by aWiebe function was used for modeling in-cylinder combustion. For studying this issue, thermodynamic models such as Woshni, Isentropic, etc. were used. Then, the experiments were carried out to validate the calculated data. The objective of the present work was to examine effect of ignition timing on the performance of an SI engine. For achieving this goal, at the speed of 3400 rpm, ignition timing was changed in the range of 41 degrees before the top dead centre to 10 degrees after TDC. By changing the ignition timing, the results of some characteristics such as power, torque, indicatory pressure, exhaust emission and efficiency were obtained and compared. The results demonstrated that optimal power and torque and the maximum efficiency were achieved at 31 degrees before the top dead centre and engine performance was improved by changing timing angle. It was also indicated that the maximum thermal efficiency could be accomplished while peak pressure occurred between 5 and 15 degrees of ATDC. The amounts of O2, CO2 and CO were almost constant but HC increased with increase of ignition timing.
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