Hydraulic and Pneumatic Systems
Mahdi Moghimi
Abstract
Using experimental models along with conducting numerical analysis have been widely used in performance recognition and optimization of hydraulic equipments. Numerical modeling has lower cost rather than experimental one; however practical tests are commonly used because of the hydraulic structure importance ...
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Using experimental models along with conducting numerical analysis have been widely used in performance recognition and optimization of hydraulic equipments. Numerical modeling has lower cost rather than experimental one; however practical tests are commonly used because of the hydraulic structure importance especially in dams. Meanwhile numerical methods could be used for future designs through validating numerical models. In this paper, volume of fluid method, VOF, has been employed to simulate the free surface flow at the dam bottom outlet form bell mouth section up to the downstream channel. Since the flow through the gates has high Reynolds number, the standard k-ε and also Reynolds Stress Model, RSM, turbulence models is used and the results compared. The discharge coefficient and the ventilated air velocity through the vents is computed numerically and compared with the experimental data. Comparison between the experimental data and numerical simulation results shows good compatibility, especially in RSM turbulence model rather than k-ε turbulence model. The results show that the maximum error percentage in simulation of the discharge coefficient and the ventilated air velocity is 9% and 3% respectively.
Computational Fluid Mechanics (CFM)
S. Rasoolzadeh; M. Y. Hashemi
Abstract
The purpose of this paper is to numerically simulate unsteady, incompressible, and laminar flow with natural and mixed convection heat transfer in a square lid-driven cavity filled with Cu-Water nanofluid. Jameson method is used in conjunction with the Artificial compressibility method on the unstructured ...
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The purpose of this paper is to numerically simulate unsteady, incompressible, and laminar flow with natural and mixed convection heat transfer in a square lid-driven cavity filled with Cu-Water nanofluid. Jameson method is used in conjunction with the Artificial compressibility method on the unstructured grid in a viscous flow. Effects of Grashof number and nanoparticle volume fraction on the flow and heat transfer characteristics are investigated. Two-dimensional Navier-Stokes equations as the governing equations of the problem are discretized with the finite volume method. Spatial discretization is performed with a two-order central scheme; and Jameson artificial dissipation terms are added to equations to stabilize the solution. Unsteady terms are discretized with an implicit two-order scheme and are solved with fourth-order explicit Runge-Kutta method in pseudo-time. It is found that the Jameson method has good performance with a reasonable convergence rate. Results show that an increase in the volume fraction of nanoparticles improves heat transfer characteristics while the increase in the Grashof number, weakens the heat transfer due to the domination of natural convection.
Mechanics of Materials
Fulufhelo Nemavhola; Simon Dhlamini; Rudzani Sigwadi; Touhami Mokrani
Abstract
This paper presents the results of mechanical strength of wet and dry zirconia/ Nafion® nano-composite membrane. The tensile tests were conducted to determine elastic modulus and stiffness of dry and wet pristine Nafion® membrane and modified Nafion® membrane. The composite membranes were ...
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This paper presents the results of mechanical strength of wet and dry zirconia/ Nafion® nano-composite membrane. The tensile tests were conducted to determine elastic modulus and stiffness of dry and wet pristine Nafion® membrane and modified Nafion® membrane. The composite membranes were prepared by recast method of different synthesized zirconium oxide with the zirconia content of 10% by weight. The uniaxial mechanical properties of nano-composite membranes and recast Nafion® membrane were captured using a CellScale UStretch uniaxial testing system. The length, width, and thickness of samples were measured using a Vernier caliper and recorded prior to testing. It was found that elastic modulus of the wet Nafion recast is 62.06 %, 35.26 %, 30.79 % and 35.26 % higher than that of Nafion®/ Zr-100, Nafion/® Zr-80, Nafion®/Zr-50, and Nafion®/Zr-0, respectively. The elastic modulus of dry Nafion recast, Nafion®/Zr-100, Nafion®/Zr-80, Nafion®/Zr-50, and Nafion/Zr-0 membranes are 46.29 %, 83.31 %, 64.81 %, 59.84 %, and 78.36 % higher than those of wet Nafion® recast, Nafion®/Zr-100, Nafion®/Zr-80, Nafion®/Zr-50, and Nafion®/Zr-0 membranes, respectively. Furthermore, the results showed that when the water content increases in the nano-composite membranes the mechanical strength also decreases.
Dynamic Response
J. Akbari; H. Valaei; M. F. Sepahvand
Abstract
Finite-element modeling of structures using elements without rotational degrees of freedom (DOFs) is usually stiffer than their physical behavior. Therefore, the stiffness of a structural system will be smoothed by adding rotational DOFs in the numerical model. In the traditional displacement-based ...
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Finite-element modeling of structures using elements without rotational degrees of freedom (DOFs) is usually stiffer than their physical behavior. Therefore, the stiffness of a structural system will be smoothed by adding rotational DOFs in the numerical model. In the traditional displacement-based finite-element method, adding drilling rotations is not easy. The main contribution of this paper is performing dynamic analyses using the finite strip element with added drilling rotations to the elements. For this purpose, any quadrilateral area is divided into two independent sets of orthogonal strips comprising truss and Bernoulli-Euler beam elements. Then, by using new shape functions, mass, damping, stiffness matrices, and equivalent nodal forces are derived. Finally, time history analysis for plane stress or strain type problems for direct earthquake records is performed using the developed formulations. The numerical studies show that the results of the finite strip element method using coarse meshes are competitive with the results of the finite-element method using fine meshes. This advantage is valuable in time-consuming computational problems, e.g., dynamic or nonlinear analyses.
Heat and Mass Transfer
Hasan Najafi Khaboshan; Hamid Reza Nazif
Abstract
In this research, the convective heat transfers of turbulent water fluid flow in alternating oval tubes is studied using computational fluid dynamics. The purpose of the study is to analyze the heat transfer enhancement and secondary internal flows under different alternate angles. Also, comparing the ...
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In this research, the convective heat transfers of turbulent water fluid flow in alternating oval tubes is studied using computational fluid dynamics. The purpose of the study is to analyze the heat transfer enhancement and secondary internal flows under different alternate angles. Also, comparing the effect of two schemesfor the domain discretization to be used in the solution variables’ gradients on simulation results is investigated. The secondary flow causes an increase in the numbers of multi-longitudinal vortices (MLV) by changing the angle of pitches. These phenomena permit the cold fluid flow to stream in more paths from center to tube wall and better condition for mixing of fluids. Consequently, the heat transfer enhances by using the alternating oval tubes. However, forming the multi-longitudinal vortices causes an increase in pressure drop. Also, by raising the angle of pitches, the friction factor and the average of Nusselt number are amplified. It is also observed that the average heat transfer coefficient in the transition range is more than other areas. The mean Nussult numbers of this kind of tubes in the angles of 40, 60, 80, and 90 improved 7.77%, 14.6%, 16.93%, and 24.42%, respectively in comparison with the round tube. The performance evaluation criteria (PEC) for all alternating oval tubes under the constant inlet velocity boundary condition indicated that the highest value (PEC=1.09) had been obtained at the lowest Reynolds number (Re=10,000) in the alternating oval tube 90°.
Deepak Kumar Sharma; Tikendra Nath Verma
Abstract
The present study focuses on the optimization in the use of non-petroleum fuel derived from waste fish oil fuels, as a replacement for petroleum diesel fuel for compression ignition engine. The study comprises of comparison between results of fish oil biodiesel-diesel blends in a compression ignition ...
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The present study focuses on the optimization in the use of non-petroleum fuel derived from waste fish oil fuels, as a replacement for petroleum diesel fuel for compression ignition engine. The study comprises of comparison between results of fish oil biodiesel-diesel blends in a compression ignition engine. Fuel properties such as viscosity, density, heat value of fuel, cetane number and a flash point of fish oil biodiesel and its blends with diesel were studied. The fish oil biodiesel (60, 40, 20, and 0%) – diesel (40, 60, 80 and 100%) are blended at volume basis. The results show reduction in thermal efficiency, temperature, particulate matter and nitrogen oxides emission; while showing an increase in higher specific fuel consumption, ignition delay, carbon dioxide and smoke emissions. The B20 fuel blend improves BTE by 4.7%, CO2 emissions has been increased by 2.56%, while SFC is lowered by 7.92% as compared to diesel fuel. In biodiesel blend (B20), the highest reduction in NOx by 14.9%, particulate by 4.22% is observed although smoke emission slightly rises with an increase in fish oil in the blends, as compared to diesel fuel.
Fatigue
L. Abbasiniyan; S. H. Hoseini; S. Faroughi
Abstract
In this paper, the crack propagation and branching in the pre-cracked and notched samples have been modeled using nonlocal peridynamic theory. The bond-based peridynamic model has been numerically implemented which make it possible to simulate various features of dynamic brittle fracture such as crack ...
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In this paper, the crack propagation and branching in the pre-cracked and notched samples have been modeled using nonlocal peridynamic theory. The bond-based peridynamic model has been numerically implemented which make it possible to simulate various features of dynamic brittle fracture such as crack propagation, asymmetries of crack paths and successive branching. The fracture simulation of thin plates made of a brittle material with different crack and notch patterns has been considered. The molecular dynamics open-source free LAMMPS code has been updated to implement the peridynamic theory based modeling tool for two-dimensional numerical analysis. The simulations show that, the simulation time significantly decreases which is the core and distracting deficiency of the peridynamic method. Moreover, the simulated results demonstrate the capability of peridynamic theory to precisely predict the crack propagation paths as well as crack branching during dynamic fracture process. The good agreement between simulation and experiments is achieved.
Heat and Mass Transfer
L. Ramamohan Reddy; M. C. Raju; G. S. S. Raju; S. M. Ibrahim
Abstract
The paper aims at investigating the effects of chemical reaction and thermal radiation on the steady two-dimensional laminar flow of viscous incompressible electrically conducting micropolar fluid past a stretching surface embedded in a non-Darcian porous medium. The radiative heat flux is assumed to ...
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The paper aims at investigating the effects of chemical reaction and thermal radiation on the steady two-dimensional laminar flow of viscous incompressible electrically conducting micropolar fluid past a stretching surface embedded in a non-Darcian porous medium. The radiative heat flux is assumed to follow Rosseland approximation. The governing equations of momentum, angular momentum, energy, and species equations are solved numerically using Runge-Kutta fourth order method with the shooting technique. The effects of various parameters on the velocity, microrotation, temperature and concentration field as well as skin friction coefficient, Nusselt number and Sherwood number are shown graphically and tabulated. It is observed that the micropolar fluid helps the reduction of drag forces and also acts as a cooling agent. It was found that the skin-friction coefficient, heat transfer rate, and mass transfer rate are decreased, and the gradient of angular velocity increases as the inverse Darcy number, porous medium inertia coefficient, or magnetic field parameter increase. Increases in the heat generation/absorption coefficient caused increases in the skin-friction coefficient and decrease the heat transfer rate. It was noticed that the increase in radiation parameter or Prandtl number caused a decrease in the skin-friction coefficient and an increase in the heat transfer rate. In addition, it was found that the increase in Schmidt number and chemical reaction caused a decrease in the skin-friction coefficient and an increase in the mass transfer rate.
Fluid Mechanics
Aminreza Noghrehabadi; Mohammad Ghalambaz; Mehdi Ghalambaz; Afshin Ghanbarzadeh
Abstract
In the present paper, the flow and heat transfer of two types of nanofluids, namely, silver-water and silicon dioxide-water, were theoretically analyzed over an isothermal continues stretching sheet. To this purpose, the governing partial differential equations were converted to a set of nonlinear differential ...
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In the present paper, the flow and heat transfer of two types of nanofluids, namely, silver-water and silicon dioxide-water, were theoretically analyzed over an isothermal continues stretching sheet. To this purpose, the governing partial differential equations were converted to a set of nonlinear differential equations using similarity transforms and were then analytically solved. It was found that the magnitude of velocity profiles in the case of SiO2-water nanofluid was higher than that of Ag-water nanofluid. The results showed that the increase of nanoparticle volume fraction increased the non-dimensional temperature and thickness of thermal boundary layer. In both cases of silver and silicon dioxide, increase of nanoparticle volume fraction increased the reduced Nusselt number and shear stress. It was also demonstrated that the increase of the reduced Nusselt number was higher for silicon dioxide nanoparticles than silver nanoparticles. However, the thermal conductivity of silver was much higher than that of silicon dioxide.
Composite Materials
S. Khalilpourazary; N. Payam
Abstract
Warpage and shrinkage control are important factors in proving the quality of thin-wall parts in injection modeling process. In the present paper, grey relational analysis was used in order to optimize these two parameters in manufacturing plastic bush of articulated garden tractor. The material used ...
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Warpage and shrinkage control are important factors in proving the quality of thin-wall parts in injection modeling process. In the present paper, grey relational analysis was used in order to optimize these two parameters in manufacturing plastic bush of articulated garden tractor. The material used in the plastic bush is Derlin 500. The input parameters in the process were selected according to their effect on shrinkage and warpage values, melt temperature, mold temperature, injection rate, injection pressure, and packing pressure. Then, the Taguchi method was applied to design the experiments, and through the use of Mold Flow software injection molding process was simulated based on these experiments and the input parameters. Based on the results obtained from the simulation, the input parameters were analyzed in three levels using grey relational analysis. Then, analysis of variance and confirmation tests were carried out on the output of grey relational analysis to predict the optimum values of the input parameters and to calculate the dimensional changes of the plastic bush. Gaining these values, the plastic bush sample was manufactured, and its 3D point cloud model was generated by a scanner. At the end, by generating 3D solid model of the plastic bush its dimensional features were studied. The comparison of the warpage and shrinkage values between grey relational analysis and 3D CAD model indicates the precision of the method in controlling and measuring these two parameters.
Manufacturing Processes
Abstract
Laser bending is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. In this paper, temperature distribution in a mild steel sheet metal is investigated numerically and experimentally. Laser heat source is applied through curved paths in square sheet ...
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Laser bending is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. In this paper, temperature distribution in a mild steel sheet metal is investigated numerically and experimentally. Laser heat source is applied through curved paths in square sheet metal parts. Finite element (FE) simulation is performed with the ABAQUS/CAE standard software package. Material property of AISI 1010 is used in FE model and experiments. The aim of this study is to identify the response related to deformation and characterize the effect of laser power with respect to the bending angle for a square sheet part. An experimental setup including a Nd:YAG laser Model IQL-10 with maximum mean laser power of 500 W is used for the experiments to verify FE analysis results. It is observed that numerical results are relatively in good agreement with the experimental results. Results also show that increasing laser power increases the bending angle.
Heat and Mass Transfer
Aminreza Noghrehabadi; Mohammad Ghalambaz; Amin Samimi
Abstract
In this paper, an integration of a symbolic power series method - Padé approximation technique (PS - Padé), was utilized to solve a system of nonlinear differential equations arising from the similarity solution of laminar thermal boundary layer over a flat plate subjected to a convective ...
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In this paper, an integration of a symbolic power series method - Padé approximation technique (PS - Padé), was utilized to solve a system of nonlinear differential equations arising from the similarity solution of laminar thermal boundary layer over a flat plate subjected to a convective surface boundary condition. As both boundary conditions tended to infinity, the combination of series solutions with the Padé approximants was used for handling boundary conditions on the semi-infinite domain of solution. The combination of power series and Padé proposed an alternative approach of solution which did not require small parameters and avoided linearization and physically unrealistic assumptions. The results of the present approach were compared with numerical results as well as those of previous works reported in the literature. The obtained results represented remarkable accuracy in comparison with the numerical ones. Finally, reduced Nusselt number, as an important parameter in heat transfer, was calculated by the obtained analytical solution. The present power series-Padé technique was very simple and effective, which could develop a simple analytic solution for flow and heat transfer over the flat plate. The results of the present study could be easily used in practical applications.
Fluid Mechanics
Javad Shahbazi Karami; GH. Payganeh
Abstract
In this study, hot metal gas forming process of AA6063aluminumtubeis studied with a focus on heat transfer of both fluid and solid phases numerically. An experimental study is simultaneously conducted to validate the numerical method. Some of the most important outputs of the present study, are velocity ...
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In this study, hot metal gas forming process of AA6063aluminumtubeis studied with a focus on heat transfer of both fluid and solid phases numerically. An experimental study is simultaneously conducted to validate the numerical method. Some of the most important outputs of the present study, are velocity distribution of fluid inside the tube as well as the fluid in the gap between tube and matrices. As a result of non-homogenous distribution of temperature on tube surface, circulating flows are generated inside the tube which may have considerable effects on heat transfer phenomenon. It is seen that in 600 s after start, number of the circulating flows doubles. Analysis of temperature distribution reveals thatmiddle part of the tube reaches 500 ̊C after 600 s from process start and other parts have higher temperature. By applying an efficient control method for heater elements, temperature distribution of the tube reaches a homogenous form.
Manufacturing Processes
M. Dastagiri; P. Srinivasa Rao; P. Madar Valli
Abstract
Electro Discharge Machining (EDM) is an incredibly recognizable machining for ticklishness profiles in ’difficult to machine ‘materials. In EDM, the material ejection of the cathode is cultivated through exact controlled electric pulse (the flash), which changes the metals of two terminals ...
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Electro Discharge Machining (EDM) is an incredibly recognizable machining for ticklishness profiles in ’difficult to machine ‘materials. In EDM, the material ejection of the cathode is cultivated through exact controlled electric pulse (the flash), which changes the metals of two terminals into dissolve and vaporize, as a result of the breakdown of the dielectric medium. The most commonly used dielectric media are kerosene, paraffin, glycerin, transformer oil, and EDM oil; all are derived from petroleum. These dielectric media undergo pyrolysis and carbon soot formation is deposited on work electrode, and sometimes carbon precipitates into work. To overcome these effects vegetable oils are tried as alternate dielectric media. Pongamia Pinnetta is abundantly available in most countries; and it is cheaper and non-edible. Pongamia Pinnata (PP) oil is extracted from plant seeds, and is blended with EDM oil and several experimentations are done to find its suitability. Operational variables with respect to input and output parameters are identified. Some of these are best EWR, MRR, TWR, and SR with applied current (I), pulse on time (Ton), and pulse off time (Toff) are the ones picked as the input process factors; because for the industrial application many machinists choose these three as the input parameters; and other is constant and picked under specific requirements only. After the successful completion of this experimentations, Pongamia Pinnata oil blends are fit for the industrial application using technique of order preferancing with similar to ideal solution [TOPSIS]. It is observed that no carbon soot formation takes place in the work component with PP oil as the dielectric fluid.
Fracture Mechanics
Alireza Hassani; Amin Hassani; Mojtaba Mahmoudi Monfared
Abstract
Abstract: The solution to problem of an orthotropic long cylinder subjected to torsional loading is first obtained by means of separation valuables. The cylinder is twisted by two lateral shear tractions and the ends of the cylinder surface of the cylinder are stress-free. First, the domain under consideration ...
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Abstract: The solution to problem of an orthotropic long cylinder subjected to torsional loading is first obtained by means of separation valuables. The cylinder is twisted by two lateral shear tractions and the ends of the cylinder surface of the cylinder are stress-free. First, the domain under consideration is weakened by an axisymmetric rotational Somigliana ring dislocation. The dislocation solution is employed to derive a set of Cauchy singular integral equations for the analysis of multiple axisymmetric planner cracks. The numerical solution to these integral equations is used to determine the stress intensity factors (SIFs) for the tips of the concentric planar cracks A preliminary comparison between results of this study and those available in the literature is performed to confirm the validity of the proposed technique. Several examples of multiple concentric planner cracks are solved and displayed graphically. Furthermore, Configuration of the cracks and the interaction between cracks is studied.
Vibration
Nadia Parandeh Afshar; Farhad S. Samani; Moslem Molaie
Abstract
Recently, a large amount of studies have been related to nonlinear systems with multi-degrees of freedom as well as continuous systems. The purpose of this paper is to optimize passive vibration absorbers in linear and nonlinear states for an Euler-Bernoulli beam with a nonlinear vibratory behavior under ...
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Recently, a large amount of studies have been related to nonlinear systems with multi-degrees of freedom as well as continuous systems. The purpose of this paper is to optimize passive vibration absorbers in linear and nonlinear states for an Euler-Bernoulli beam with a nonlinear vibratory behavior under concentrated moving load. The goal parameter in the optimization is maximum deflection of the beam. The large deformation for beam modeling is considered, i.e. the relation between strains and deflections is nonlinear. The force magnitude and beam length are two effective factors for the beam deflection. Vibration absorber with linear damping and linear or nonlinear stiffness is also considered in this manuscript. The results show that, for normal forces and short beams, linear and nonlinear models have similar behaviors, while surveying nonlinear behavior is necessary by increasing the force and length of the beam, i.e. large deflections. Moreover, the difference between linear and nonlinear beam models for regular force magnitudes and beam lengths is negligible. For higher loads and longer beams, beam model nonlinearity can be important. Results demonstrate that,in the presented numerical values (train bridge application) for cubic nonlinear vibration absorber, there are two optimal locations for vibration absorber installation: one inclined from the middle of the beam to the direction of moving loads and the second which is more interestingly inclined from the middle of the beam to moving loads in the opposite direction. Moreover, depending on the model's numerical parameters, for short beams, linear vibration absorber is more effective, while for long beams, cubic nonlinear beam behaves better than the linear one.
M. Zakyani
Abstract
Large eddy simulations of non-reactive Delft II and Sydney bluff body flow are performed using different sub-grid scale models. Simulation of non-reactive burners is useful when studying flow characteristics inside reactive burners. As turbulent combustion simulation is rather an intricate task, it is ...
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Large eddy simulations of non-reactive Delft II and Sydney bluff body flow are performed using different sub-grid scale models. Simulation of non-reactive burners is useful when studying flow characteristics inside reactive burners. As turbulent combustion simulation is rather an intricate task, it is helpful to study cold air flow inside the combustion chamber before igniting the chamber. In order to study the flow inside the mentioned test cases, different sub-grid scale models, i.e., constant Smagorinsky, dynamic Smagorinsky and dynamic WALE model are used to model the unresolved small scales. For the numerical simulations, a finite volume in-house code is used. The code adopts the projection method to solve the fluid flow equations. A second-order accurate scheme is used for spatial discretization. The time integration is done using a second-order accurate predictor-corrector scheme. For solving the resultant pressure Poisson equation, TDMA (Tridiagonal Matrix Algorithm) is used with multi-grid convergence acceleration. Generally, the results show good agreement with available experimental data. As expected, the dynamic WALE model performs better than the other models. To further improve the results, a rather realistic type of velocity inlet boundary conditions are applied to Sydney bluff body flow, i.e., digital filter velocity inflow boundary conditions. The results show drastic improvement using digital filter inflow, which is mainly due to the turbulent nature of the flow field.
Heat and Mass Transfer
T. Sudhakar Reddy; M. C. Raju; S. V. K. Varm
Abstract
In the present paper, an analysis was carried out to investigate effects of radiation on a free convection flow bounded by a vertical surface embedded in a porous medium with constant suction velocity. It was under the influence of uniform magnetic field in the presence of a homogenous chemical reaction ...
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In the present paper, an analysis was carried out to investigate effects of radiation on a free convection flow bounded by a vertical surface embedded in a porous medium with constant suction velocity. It was under the influence of uniform magnetic field in the presence of a homogenous chemical reaction and viscous dissipation with constant heat and mass flux. The non-dimensional governing equations were solved analytically and the expressions were found for velocity, temperature and concentration fields. Also, the expression for skin friction near the plate was derived and the results were discussed in a table.
Hydraulic and Pneumatic Systems
Lokesh Kumar; Nimai Pada Mandal
Abstract
This study focuses on the flow and pressure fluctuations of a fixed displacement radial piston pump with a valve plate with silencing grooves, and the effect of the number of pistons (5, 6, and 7) is investigated. Over the manifolds of the pump, valve plate silencing grooves are regarded as Top Dead ...
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This study focuses on the flow and pressure fluctuations of a fixed displacement radial piston pump with a valve plate with silencing grooves, and the effect of the number of pistons (5, 6, and 7) is investigated. Over the manifolds of the pump, valve plate silencing grooves are regarded as Top Dead Center and Bottom Dead Center. The mathematical modeling is run in MATLAB Simulink. Analyzing the flow characteristics and volumetric efficiency of the pump with and without silencing groove valve plate configuration of the pump is done. The opening and closing area pattern of the kidney port is also analyzed. The percentage reduction of flow and pressure fluctuation with the silencing groove is 19% and 16.16%, respectively, for Z = 7, as compared to the model without silencing groove valve plate. The volumetric efficiency of the model with silencing groove valve plate is improved from 1% to 2% as compared to the model without silencing groove valve plate. The lower the flow and pressure fluctuation coefficients, the higher the flow rate and volumetric efficiency of the pump for the model with silencing groove valve plate.
Plasticity
Sadjad Pirmohammad; Sobhan Esmaeili-Marzdashti; Arameh Eyvazian
Abstract
In this article, crashworthiness performance and crushing behavior of tapered structures with four internal reinforcing plates under axial and oblique dynamic loadings have been investigated. These structures have a tapered form with five cross sections of square, hexagonal, octagonal, decagon and circular ...
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In this article, crashworthiness performance and crushing behavior of tapered structures with four internal reinforcing plates under axial and oblique dynamic loadings have been investigated. These structures have a tapered form with five cross sections of square, hexagonal, octagonal, decagon and circular shape. In the first step, finite element simulations performed in LS-DYNA were validated by comparing with experimental data. The code generated in LS-DYNA was then used to investigate energy absorption behavior of the tapered structures. Response surface methodology and historical data design technique were employed to optimize the cross section perimeter (tapered angle) of the tapered structures by considering two conflicting crashworthiness criteria including EA (energy absorption) and PCF (peak crushing force). The optimization results showed that the optimal tapered angle enhanced by increasing the number of cross section sides (or number of corners). Then, the optimized tapered structures with different cross-sections were compared with each other using a ranking method called TOPSIS to introduce the most efficient energy absorber. The decagonal structure was finally found to be the best energy absorber.
Internal Combustion Engine
A. Shaafi; M. J. Noroozi; V. Manshaei
Abstract
In this computational research, the separate and simultaneous impacts of diesel direct injection timing, fuel spraying cone angle, and hydrogen gas addition on combustion characteristics, output emissions, and performance in a single-cylinder direct injection diesel engine was studied. In order to conduct ...
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In this computational research, the separate and simultaneous impacts of diesel direct injection timing, fuel spraying cone angle, and hydrogen gas addition on combustion characteristics, output emissions, and performance in a single-cylinder direct injection diesel engine was studied. In order to conduct the simulations, valid and reliable models for combustion, break-up, and for turbulence was used. The effects of fifteen fuel injection strategies based on characteristics such as time of fuel spraying (-15, -10 CA BTDC, and TDC) and nozzle cone angle (105, 115, 125, 145, and 160 degrees) under neat diesel combustion and diesel-hydrogen combustion engine operations conditions were explored. The obtained results indicated that the addition of H2 due to significant heating value has increased indicated power and improved indicated specific energy consumption at the expense of NOx emissions but considerably decreased CO and soot emissions simultaneously. By advancing injection timing, maximum pressure peak point, maximum temperature peak point, and maximum heat release rate peak point have increased and caused lower indicated specific energy consumption. However, using a wide spray angle (e.g., 160 cone degrees), resulted in lower indicated power and higher indicated specific energy consumption due to more fuel could spray in regions with lower oxygen concentrations compared to baseline operation case.
Manufacturing Processes
Hasan Ghafourian Nosrati; Mahdi Gerdooei
Abstract
In recent years, most industries such as the aerospace, automotive, and others have been pushed to methods for reducing costs. One of these methods is the rubber pad forming (RPF) process, which has been given more attention as a low-cost method than conventional methods. In RPF, unlike conventional ...
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In recent years, most industries such as the aerospace, automotive, and others have been pushed to methods for reducing costs. One of these methods is the rubber pad forming (RPF) process, which has been given more attention as a low-cost method than conventional methods. In RPF, unlike conventional methods which mainly use metals as tools, one of the tools will be made of elastic pads. The RPF process has attracted the attention of many researchers around the world. Researchers from Iran started their work in this field around 2001 and subsequently published several remarkable articles. The first published Iranian study of the RPF process dates back to 2003, indicating that the use of flexible tools has a history of two decades in Iran. However, in the last decade, the number of published Iranian articles in the RPF process field and the introduction of new methods based on RPF and its simulation has increased. This review article aims to outline Iran's involvement in the RPF process, and it emphasizes that Iranian researchers predominantly contribute to the RPF process through simulation, experimental endeavors, and the introduction of innovative methods utilizing flexible tools.
Heat and Mass Transfer
Mohammad Riahi; Mohamad Hoseinpour Gollo; Seiied Nader Ameli Kalkhoran
Abstract
Laser forming is a modern process which is mainly used for forming metals. Different Lasers are used in this regard that includes Nd: YAG and CO2. In this study, forming bi-layer sheets of Aluminum/Ceramic by Laser was investigated. Furthermore, effect of Uniform and Gaussian heat flux distribution in ...
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Laser forming is a modern process which is mainly used for forming metals. Different Lasers are used in this regard that includes Nd: YAG and CO2. In this study, forming bi-layer sheets of Aluminum/Ceramic by Laser was investigated. Furthermore, effect of Uniform and Gaussian heat flux distribution in different power, velocity, and beam diameters on bending angle was studied. FEM simulation indicated that, in the same conditions of analysis, Uniform heat flux distribution caused higher bending angle than Gaussian heat flux distribution. Moreover, the results showed that there was an optimum point at different speeds and laser beam diameters, at which the bending angle was maximum. In order to evaluating the numerical results, a set of experiments was conducted, which showed good agreement.
Fluid Mechanics
Gh. Payganeh; A. Hadidi; M. Hallaji; N. Garjasi
Abstract
Over the last ten years, robustness of schemes has raised an increasing interest among the CFD community. The objective of this article is to solve the quasi-one-dimensional compressible flow inside a “Shubin nozzle” and to investigate Bean-Warming and flux vector splitting methods for numerical ...
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Over the last ten years, robustness of schemes has raised an increasing interest among the CFD community. The objective of this article is to solve the quasi-one-dimensional compressible flow inside a “Shubin nozzle” and to investigate Bean-Warming and flux vector splitting methods for numerical solution of compressible flows. Two different conditions have been considered: first, there is a supersonic flow in the entry and a supersonic flow in the outlet, without any shock in the nozzle. Second, there is a supersonic flow in the inlet and a subsonic flow in the outlet of the nozzle and a shock occur inside the nozzle. The results show that the run time of the flux vector splitting scheme is more than the Bean-Warming scheme, and, the flux vector splitting scheme is more accurate than the Bean-Warming scheme. However the flux vector splitting scheme is more complicated.
Forming
Hashem Zamanian; Mehdi Bostan Shirin; Ahmad Assempour
Abstract
In this work, an inverse finite element formulation was modified for considering material anisotropy in obtaining blank shape and forming severity of deep drawn orthotropic parts. In this procedure, geometry of final part and thickness of initial blank sheet were known. After applying ideal forming formulations ...
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In this work, an inverse finite element formulation was modified for considering material anisotropy in obtaining blank shape and forming severity of deep drawn orthotropic parts. In this procedure, geometry of final part and thickness of initial blank sheet were known. After applying ideal forming formulations between material points of initial blank and final shape, an equation system was obtained in terms of unknown initial positions on the blank sheet. Initial positions of material points were obtained by solving this equation system. In this algorithm, the Hill's anisotropic plasticity and associated plastic flow rule were used. Strain distribution on the final part was obtained by comparing the initial blank and final part. The method was applied for the simulation of drawing an orthotropic blank to a rectangular cup. Accuracy of the presented method was evaluated by comparing the results with numerical forward method and experiment results.
