Modares Mechanical Engineering
Year:2018 | Volume:18 | Issue:4 |Papers Count:30

Increasing of capacity in lead-acid batteries and reducing charging time in lower temperature are considered as some main challenges of designers and manufacturers. Geometrical properties of battery plates such as thickness and maximum activated area are some of effective parameters on battery performance. Thus, determining of optimum values for independent variables is an important problem for battery industry. In the present study, a numerical solution code is developed using computational fluid dynamic method to simulate battery behavior. Numbers of 50 runs are suggested using response surface method. For each response one empirical model is extracted as a function of independent variables and from these models the optimization process is done. The results shows that in positive electrode thickness of 0. 078 cm, negative electrode thickness of 0. 53 cm, separator thickness of 0. 04 cm and maximum activated areas for positive and negative electrode of 80 cm-1 is an optimum condition to get maximum capacity, minimum charging time and temperature. A confirmation test is done and it demonstrates that the results are in good agreement to predicted optimum results. In conclusion, the present study shows that by changing geometrical properties of the battery one can improve its performance.

The use of new energies, including geothermal energy, is rapidly devoloping in the world. In Iran, the Sabalan area has a great potential for generating energy from geothermal energy sources. In this paper, a new power generation combined cycle (flash combined cycle with supercritical carbon dioxide and organic Rankine cycle) is proposed with respect to two wells with different temperatures and pressures for Sabalan geothermal sources. For the organic Rankine cycle, four fluids are considered appropriately and then proposed combination cycle is investigated by energy and exergy analysis. In this study, a new method proposed for the determination of Pinch point for carbon dioxide heat exchangers. In the end the proposed cycle has been optimized relative to seprators pressure, the second evaporator temperature and the carbon dioxide cycle pressure ratio. The results show that the n-butane agent has been selected as the most suitable fluid for the Rankine cycle. For the optimal condition, the net power of the proposed cycle is 19934 kW, the cycle efficiency will be 17. 05% and the exergy efficiency will be 65. 38%. The results of exergy analysis show that the low pressure turbine in geothermal have the highest value of exergy destruction. The results show that net power output, energy and exergy efficiencies of the proposed cycle in this paper is 15. 29 %, 17. 06% and 18. 35% higher than the corresponding values obtained for the previously proposed system.

Large and/or complicated sandwich structures are often manufactured by connecting pre-fabricated sandwich panels by means of connections, adhesive or bolts. In nearly all sandwich constructions certain types of joints have to be used for assembly but little is known about their mechanical behavior. This paper deals with the investigation of the behavior of two aluminum joints with different geometries under low velocity impact tests. These two joints are used to connecting sandwich panels with glassepoxy skins and aluminum honeycomb core. The joints and sandwich panels are connected by means of epoxy resin. After construction of the specimens, low velocity impact tests were performed on the specimens. Finite element analysis were used to simulate the behavior of sandwich panels with connection. Verification of the numerical results was performed by comparing the numerical and experimental results. There was a good compliance between numerical and experimental results. Also, the effect of increasing the length and the thickness of the connections on the behavior of the sandwich panel was done through a parametric study using the FEM model.

In this research, three-layered composite of brass-IF steel-brass was fabricated by cold roll bonding process (CRB) and formability of composite were investigated. Due to high work hardening of composite during rolling process, specimens were heat treated at annealing temperatures at 500° Ϲ through 700 ° Ϲ for 10 min. Formability properties of composite were investigated by using tensile, anisotropy and Erichsen tests. The results showed that, heat treatment after rolling resulted in occurrence of recrystallization phenomenon in composite, consequently a reduction tensile strength and rising strain hardening rate. Dome height created by Erichsen test prior to heat treatment was 10. 53 mm, by annealing composite at 500 ℃ , Dome height reached at 14. 62 mm. By increasing annealing temperature to 600℃ and owing to relatively high stacking fault energies of IF steel, recrystallization solitary occurred in brass layer. Nevertheless, as a result of upward trend of annealing temperature up to 650 ℃ as well as resultant driving force, recrystallization occurred in all layers and gradient of formability properties increased. As at 700℃ , recrystallization phenomenon was completed in the composite and dome height was peaked at 17. 29 mm. Moreover, by increasing annealing temperature, normal anisotropy and planer anisotropy respectively increased and decreased. Anisotropy properties of composite in comparison with brass and IF steel during complete recrystallization, it was clear that production of brass-IF steel-brass composite caused to improve normal anisotropy in brass and reduce negative effects of planer anisotropy in IF steel.

The impact problems associated with water entry have important applications in various aspects of naval architecture and ocean engineering. Also the calculation of impact force is favorable to many researchers. The purpose of this study is to simulate the impact problem of a wedge into the Newtonian and also Herschel Bulkley dilatant non-Newtonian fluids using the Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method. Some non-Newtonian fluids, such as dilatant or Herschel Bulkley dilatant fluids can resist against the wedge entry due to their shear thickening effect. In this research a prediction and correction algorithm is used to solve the governing equations. Density correction and also artificial viscosity (which is used only in Newtonian fluids) are used to prevent the numerical instability. To show the validation, ability and robustness of the generated code to capture the free surface in Newtonian and non-Newtonian fluids, the dam break problem with the image boundary condition is simulated. After validating the code and the used method, the impact problem of a wedge with Monaghan repulsive force boundary condition in Newtonian and Herschel Bulkley Dilatant non-Newtonian fluids are investigated and the results of force, pressure coefficient and velocity of the wedge are presented and compared with experiments and also with each other. To save time, the initial values of hydrostatic pressure are imposed as an initial condition of the fluid.

In this study, the effects of impact of a projectile on a fuel tank are studied using the finite element method and compared with experimental method. Due to penetration of the bullet into the tank, large internal pressures from the fluid are imposed on the tank's walls which can damage it. The considered fluid structure interaction (FSI) problem is solved in an Eulerian-Lagrangian reference frame by using the LS-Dyna software. By comparing of the results obtained from the simulations and the experimental data, it can be seen that the LS-Dyna software is able to model the different phases of event accurately. In previous researches mostly the penetration and cavitation phases are investigated numerically. In this paper all phases namely penetration, cavitation, stresses applied to tank’ s walls and bullet exit are investigated. The comparison between the Von Mises stress of walls in the fluid-filled tank and the empty one signifies 30 percent growth of the maximum Von Mises stress in the wall of the fluid-filled tank compared to the walls of the empty tank. Also in addition to what has been done in previous numerical works, the failure mode of fluid-filled tanks are determined numerically. The numerical results show that because fluid-filled tank walls are pre-stress due to the fluid shock waves, the failure mode of fluid-filled tank is quite different with the failure mode of the empty one.

Turbine tip leakage flow is one of the effective factors in reducing the efficiency and performance of axial turbines, which can also destroy turbine blades. Accordingly, it is important to identify and control the tip leakage flow. In this paper, the effect of tip clearance sizes and changes in tip shape as a passive control method on tip structure and total turbine flow performance is investigated. For this purpose, the flow loss in a two-stage axial turbine is performed using the CFX software. In order to ensure the accuracy of the results, the turbine performance curves were compared with the experimental results which good consistency has been observed. Considering the four cases for tip clearance size (0. 5% to 3% of blade span), the turbine performance curves and pressure loss have been derived. It was found that increasing the tip clearance size leads to reduced efficiency and increased losses in the axial turbine. In the following, we examine the application of the passive control method through the change of the tip geometry. In this regard, the shape of the blade tip is somehow considered that the tip clearance size is variable from leading edge to trailing edge. The results show that in these cases, tip leakage flow and the resulting vertices are weakened, which leads to a decrease in the rotor loss coefficient. Observing the flow contours results in lower temperatures in the blade region due to the formation of a weaker tip leakage flow, which helps cooling the turbine blades.

Cancer is one of the main causes of mortality and morbidity worldwide, Using a single treatment plan for all of the patients is not efficient due to the biological heterogeneity in the individuals, In order to personalize the therapy plan, tumors behavior in each patient must be understood, For this purpose clinical information of the patients are used, Mathematical modeling has gained significant interest in tumor growth investigations, due to its higher flexibility than the other methods, Mass effect and the reaction terms are the key parameters that are investigated in this paper, This is the first time that the effects of these parameters are considered in brain tumor growth modeling and there are few researches that have used personal medical images in this area, The mathematical models are used for predicting the growth of brain tumors based on personal MRIs and introducing intracellular fraction into the model, Results of the comparisons show that considering the mass effect in the growth model would improve the prediction, Furthermore, it is necessary to define the optimum formulation for reaction term according to patients' medical information, to be used in the personalized model of tumor growth prediction, The represented approach can be used as a basis for personalizing the therapy plan in patients with brain tumors,

Composite tubes may be subjected to impact loads during placement or operation. By determining the impact properties of composite tubes and using them in the design process, the accuracy of the behavior of these structures in the loading condition is guaranteed. In this study, the behavior of glass/epoxy composite tubes under dynamic axial loading was experimentally investigated. Also, the effects of parameters such as fiber density, fiber alignment angle, internal diameter of the tube and impact energy on the amount of pipe damage were also studied. To prepare composite specimens, E-type glass fiber was used with two different densities of 200 gr⁄ m2 and 400 gr⁄ m2. The specimens were placed on a drop weight machine of Tafresh University by a fixture, and the Impactor was released from the height of 2 meters. The force-displacement diagrams for each test were extracted and compared with each other. Also, a parameter called specific energy absorption was calculated for all samples in order to compare the efficiency of the samples as energy absorber. The results of this study showed that increasing the fiber density, number of layers and diameter of the tube increases the specific energy absorption. It was also observed that with the increase of the axial dynamic impact energy, the mechanical properties of the specimen will be changed and the specimen will be firmly established.

In this research, an analytical method is presented for predicting the viscoelastic and dynamic behavior of polymer nanocomposite. The analytical model is achieved by coupling the SUC micromechanical model with standard linear solid model. Boltzmann superposition principle is used to develop the constitutive equations. First, the strain associated with a relaxation experiment is considered, and then by using the idea of linearity as embodied in the Boltzmann superposition principle, the resulting stress history is predicted. Eventually, the creep function corresponding to the relaxation modulus is obtained and the hysteresis loop for nanocomposite material is represented. Creep response is sinusoidal in time and a function of stress history. Loss and storage modulus and material behavior in Laplace domain are obtained using standard linear solid model and SUC micromechanical model, respectively. Standard linear solid model is achieved by paralleling the Kelvin model with Maxwell model. The model is validated with experimental results. Effects of different interphase thickness, CNT volume fraction and phase angle on hysteresis loop is studied. Obtained results reveal that increasing the CNT volume fraction and phase angle leads to decreasing and increasing the nanocomposite hysteresis loop area, respectively. Also, Interphase thickness contains considerable effects on the nanocomposite dynamic behavior.

Operational modal analysis (OMA), as a branch of the system identification, plays a very important and practical role in determining the dynamic characteristics of the structures. In the operational approach that is implemented based on the ambient vibration test, the ambient and operation loads are considered as the excitation source of the structure. In the present research, the health monitoring of a concrete arch dam is done using the modal identification of the structural system based on an integrative method composed of frequency domain decomposition and wavelet transform, called FDD-WT method. In the integrative method that is proposed to eliminate the shortcomings of the FDD method in determining the damping values, the spectrum of the first singular value obtained from the single frequency signals extracted from the wavelet transform of the correlation functions of the vibrational responses is used to determine the damping values. In this paper, Pacoima arch dam is selected as the case study and the seismic records related to 1994 Northridge, 2001 San Fernando and 2008 Chino Hills earthquakes are also used to evaluate the dynamic characteristics and structural health monitoring during the period between 1994 to 2008. In addition, the wavelet transform of the seismic responses is also calculated in order to verify the results and to evaluate the time and frequency position of the system modes during the above-mentioned earthquakes. Investigation of changes in the natural frequencies of the structure indicates that the dam had taken serious damage during 1994 Northridge earthquake (about the fourth second), while the vibrations of the concrete structure has been almost linear during the first 4 seconds of the earthquake and also in 2001 and 2008 earthquakes.

In two-dimensional flow measurement using hot wire anemometer, directional sensitivity (angular response) of sensor plays an important role in the measurement accuracy. The angular response of the sensor describes the relationship between flow velocity vector and heat transfer from the sensor, which is determined by a sensitivity function. In this paper, two sensitivity functions, namely cosine law and Hinze equation, have been studied using wind tunnel experiments to evaluate the effect of various parameters such as flow conditions (velocity and direction), probe aspect ratio (l/d) and probe operational condition (sensor temperature) on the range of applicability of cosine law and magnitude of the sensitivity coefficient, k. Results show that the angular range of applicability of cosine law depends on flow and probe conditions. At 1% measurement error, the range of applicability of cosine law for flow measurements of velocities exceeding 10 m/s was found to be in the range of ± 30º . Moreover, at geometrical ratios higher than 600, two-dimensional flow measurements using the cosine law presents results with acceptable accuracy. In addition, the sensitivity coefficient is completely dependent on flow condition and probe aspect ratio, and its value decreases with increase in flow angle and velocity and reduction in probe aspect ratio. The results of this research can be used in the selection and proper design of probes for two-dimensional flow measurements using hot wire anemometers.

In this paper, an optimal robust nonlinear model predictive controller based on harmony search algorithm is designed for a type of 3-DOF translational parallel robot. Dynamic model of the mechanism is derived using Lagrange method and the model predictive controller augmented by uncertainty estimator is designed and stability is proved by Lyapanov theorem. Performance of the designed controller is evaluated in different conditions such as presence of disturbance and parameter variation. Furthermore, an optimal trajectory consisting four circular obstacles is designed as the reference trajectory of the robot. In order to obtain the optimum control parameters, an objective function combining control signal rate and error is considered and minimized by harmony search algorithm. In order to compare the performance of the designed controller with other nonlinear controllers, two controllers, an optimal sliding mode and a feedback linearization controller are also designed and their results are compared. Simulation results depict the desirable performance of the three controllers in spite of disturbance and model uncertainty, however, error criteria indicate priority of the robust nonlinear model predictive controller over the two other controllers.

Delamination is one of the major failure modes of the laminated composite material,which is responsible for the stiffness degradation of these materials,Hence,it is necessary to investigate this damage mechanism in these types of materials in order to distinguish their behaviors and their effects on the residual strength of the composite laminates,In this paper,a very capable procedure is proposed to assess delamination using Acoustic Emission (AE) method in composite laminates,Firstly,a novel procedure was established to decompose the fundamental Lamb wave modes in small size specimens,The damage mechanisms in End Notched Flexure (ENF) in woven and unidirectional specimens were then distinguished using Fuzzy Clustering Method (FCM),Subsequently,the crack-arrest phenomenon was inspected in each specimen,Next,experimental and Cohesive Zone Modeling (CZM) methods were done to characterize the delamination using ENF specimens,The results displayed how,it is possible to effectively reduce the effect of propagating media such as attenuation of AE signals using the new proposed procedure,In conclusion,the results of this research could lead to proficiently distinguishing different damages in laminated composite using AE Lamb-based technique,

Due to unique properties, grid stiffened composite cylinder shells are used extensively in aviation, marine and automotive industry. In recent decades, several studies are done to predict the critical buckling load of grid stiffened composite cylinder shells without breakdown or failure. Vibration Correlation Technique (VCT) is one of the most important non-destructive methods that based on nonlinear vibration analysis. The aim of this research is the prediction of the critical buckling load of stiffened composite cylinder shells with lozenge grid by using VCT. For this purpose, linear and nonlinear vibration analysis of composite cylindrical shells were performed in different compressive loads by using finite element software ABAQUS, firstly. In the next step, linear buckling critical load was determined by using numerical methods. Then, non-linear critical buckling load of grid stiffened composite cylinder shells was predicted by using VCT. To validate the results of VCT, five composite cylindrical shells were fabricated by using filament winding method with same conditions and was placed under axial compression test. Finally, the critical buckling load was measured experimentally. The results show that the difference between the critical buckling load of VCT with experimental buckling load is less than 3%. This subject implies that VCT is suitable for prediction of critical buckling load of stiffened composite cylinder shells with lozenge grid with very high accuracy.

There exist satisfactory results in the analysis of the motion control of the vehicles with the assumption of nonslip (pure rolling) condition of robot wheeles, But unfortunately in practice due to the presence of uncertainties such as sliding of wheels especially in agriculture applications where working conditions are rough the results and the quality of the control performance of the system are affected. The ideal control of wheeled systems is performed with the assumption of the existence of nonholonomic non-slip constraints, while in the real system these constraints are violated due to the presence of slippages. In this paper the problem of trajectory tracking control of wheeled vehicles in the presence of sliding is addressed. To take sliding effects into account, sliding models are introduced into the kinematic model. In other words, these effects are added as unknown parameters to the ideal kinematic model. For taking into account the sliding effects their mathematical models are introduced in system kinematic model. In another word these effects as an unknown parameters are added to the system ideal kinematics. An integrating parameter adaptation technique and backstepping control algorithm has been utilized in order to control the system. The backstepping control law is designed to track the reference trajectories and make the robot asymptotically stable around the reference trajectories. Obtained results show that the proposed adaptive controller can guarantee tracking reference trajectories in the presence of sliding of wheels. Finally, the obtained results are presented for tracking reference trajectories and comparison results shows the efficiency of using the estimation of slips in control of the system.

One way of reducing the cutting zone temperature is the use of an appropriate coolant. Common coolants, in addition to the adverse health effects on operator, cause environmental pollution as well. Because of this, interest in dry machining or green cooling methods in recent years has been greatly increased. Cryogenic cooling is one of the green cooling methods where liquid nitrogen is usually used as coolant. In the present paper, the effect of cryogenic cooling by liquid nitrogen on the cutting tool temperature and wear in turning process of AISI 304 austenitic stainless steel has been investigated. Among different methods of cryogenic cooling, the spraying technique due to its direct effect on the cutting zone has been selected. Turning with dry, wet (conventional) and cryogenic cooling methods are done. The obtained results indicated that the cryogenic cooling decreased the tool temperature compared to the dry and wet machining by 83% and 67%, respectively and reduced the flank wear of the tool by 75% and 53%, respectively. Analysis of variance showed that cutting speed relative to feed rate has a much greater impact on the tool temperature and wear. Increase of cutting speed in all cooling cases increased the tool temperature and wear.

In this research, an influence of topology optimization in energy absorption of lattice core sandwich beams by using ABAQUS software was an investigation. Relationships between the force and displacement at the midspan of the sandwich beams were obtained from the experiments. Two types of Steel lattice cores with three cell orientation were subjected to the low-velocity impact test under threepoint bending. The core of sandwich beams was made from expanded metal sheets and a topology optimization with Solid Isotropic Microstructure with Penalization (SIMP) method was used to remove the redundant expanded metal cell. In the following, by studying the topology optimization to evaluate the impact parameters, including Specific Energy Absorption (SEA), as discussed testing purposes. The energy absorbing system can be used in the aerospace industry, shipbuilding, automotive, railway industry and elevators to absorb impact energy. Experimental and numerical results showed that topology optimization could significantly increase specific absorbed energy. Results of three-point bending crushing tests showed that the SEA of a sandwich beam with optimal core structure increased between 45% and 94% compared to the initial design structure of the core. In addition, appropriate orientation of expanded metal cell in the core of sandwich beam caused to increase the specific energy absorption by more than 90%. Finally, an appropriate optimal geometric structure with three tape of volume fraction and the best examples of criteria considered with respect to the objectives were introduced.

Welding is very important in the aerospace industry and widely used in aerospace structures. One of the problems that most industries are facing is created residual stress by the welding process. Residual stresses in the surrounding areas of welding can cause cracks and crack growth so identify and evaluate of residual stresses in the welded structures is necessary. There are different methods for determining the residual stress. In this paper, the laboratory and numerical methods were presented for determining the residual stress. Then, the welding process of two aluminum sheets of 6061-T6 alloy has been done and the residual stresses have been obtained by drilling method. Welding is done in two passes and by spot welding the first, the end and the middle of the weld line are connected to prevent the sheets from moving. Also, the welding process of the two aluminum sheets was simulated in 3D in the ABAQUS finite element software and the residual stresses were extracted. All conditions in the finite element analysis are similar to the welding conditions in the laboratory. Results show high accuracy in the modeling of finite element processes in the welding process. Finally, the effect of residual stress in the value of natural frequencies is studied.

With the development of computers, the application of numerical methods in solving engineering problems has increased considerably. Methods such as Finite Element Method, Finite Volume Method and Finite Difference Method can be mentioned as some. In this research a Boundary Element Method is applied for numerical simulation. The main difference among the Boundary Element method and other numerical methods is the governing mathematics. At first In this method the governing equation is integrated. This leads to a decrease in the dimensions of the problem and then the simulation is performed. In this research, by a change of variable, the Navier Stokes equation is transformed to Navier equation in Elastostatics at first. Subsequently the methods proposed for solving the problems in Elastostatics is utilized to solve the viscous fluid flow. In fact, the applied fundamental solution is the main difference among the proposed method and other Boundary Element Methods. In the proposed method the fundamental solution of the Navier equation is utilized for simulation. At last, by considering the governing mathematics a computer code is developed for viscous flow simulation. The code is applied to two different geometries, a lid-driven-cavity and a backward facing step. Convergent solutions is achieved up to Reynolsds numbers equal with 600 and 100 respectively.

Hydrogen has become an attractive source of energy for transportation industry, which is adaptable to the environment. Using composite pressure vessel type IV for storing compressed hydrogen gas seems to be a safety solution because of their ratio of strength to weight. Type IV composite pressure vessels consist of three main parts of polymeric liner, metallic boss and carbon fiber/epoxy composite shell. In the dome zones of these vessels, the thickness of composite layers and the fiber angle would increase because of accumulation of resin and reduction in radius. This issue is caused the modeling of these vessels to be a serious challenge. The WCM plug-in is presented for simulation of axisymmetric or three-dimensional composite pressure vessels type III and IV in ABAQUS software. In addition to the parameters like layer thicknesses and fiber angles, manufacturing parameters such as bandwidth, transition angle and end fraction could be also defined in this plug-in in order to achieve more accurate results. In this study, a type IV high pressure composite vessel with inner volume of two liters is modeled using the WCM plug-in in ABAQUS software. Numerical results are assessed by the available experimental results in the literature. Moreover, failure pressure of this vessel has been estimated by calculating the on-axis stresses and using failure criteria such as Tsai-Hill, Tsai-Wu and Hashin which is not done in other investigations.

Heat transfer enhancement is widely applicable in various industries, specifically in heat exchangers. Optimizing of heat transfer in the absence of increased pumping energy will result in increased of total efficiency in different systems. In this paper, forced convection heat transfer and fluid flow of fully developed laminar regime in a horizontal tube under uniform and non-uniform step heat fluxes is investigated experimentally. The effect of uniform, non-uniform increasing and decreasing applied heat fluxes on heat transfer and fluid flow are investigated. The effect of various parameters on heat transfer and fluid flow characteristics in these models are reported. Uncertainty analysis is performed and acceptable maximum of 1. 8 percent is acquired. The primary results compared to well-known Shah and London equation for validation and maximum error of 8. 5 percent is reported. In the present paper, Energy and exergy are two approach of analyzing. Convection heat transfer coefficient enhancement of 19. 3 and 22. 3 percent compared with model 1 are reported for model 2 and 3 respectively, in energy analysis. Furthermore, in this paper, exergy analysis is done and irreversibility values of 0. 0887, 0. 0803 and 0. 1037 are reported for model 1, model 2 and model 3 respectively. Finally, it is concluded that the model number 3 is the best way to enhance heat transfer because of the maximum averaged Nusselt number and the minimum entropy generation values.

Detection of defects in the internal surfaces of pipes due to the inherent feature of these surfaces which is inaccessibility is always a troublesome process. In this study, a novel method has been designed for detection of defect locations on the internal surfaces of pipes and accurate estimation of defect geometrical parameters such as length and average material loss depth. The way that this method works is that a band heater is located on the external surface of the pipe in inspection segment, and specified heat flux is applied to this surface for a short time, and the temperature of these sensors located on rear of the band heater is measured during and after of applying thermal heat flux. The local temperature rise on the section of the external surface of the pipe indicates a defect on its internal surface. In this case, a defect with unknown parameters is supposed on the internal surface of the pipe, and by using the inverse heat conduction method, an iterative numerical simulation procedure continues until the unknown geometrical parameters of defects are estimated in a way to minimize the difference between the measured and simulated temperature in the location of sensors.

Nowadays, magnetic nanofluids have drawn a lot of attention toward themselves due to various applications in different fields such as medicine and industry. In this paper, for the first time new pumping method for magnetic nanofluids and ferro-fluids is presented. Moreover, magnetic nanofluid flow inside a rectangular channel under the effect of nonuniform magnetic field of permanent magnet is investigated. Iron oxide nanoparticles which lie completely homogeneous inside the based fluid of water are used. The governing equations obtained by adding the Kelvin body force term to the Navier-Stokes equations, and the equations are discretized using finite volume method and PISO algorithm. In order to study the effective parameters in the function of the FHD micro pump, a selected ranges of nanoparticles size, volume fraction of nanoparticles, saturated magnetization, and the length and width of the magnet are studied. The results demonstrate the increase in any of the mentioned parameters leads to rise in velocity magnitude inside the channel. Change in the diameter of magnetic nanoparticles has greatest effect on the velocity magnitude inside the channel. Furthermore, vertical magnet has better performance than horizontal one in FHD micro pump.

This study aims to investigate the transverse vibration of single-and double-layered graphene sheets embedded in an elastic medium based on the third-order shear deformation theory considering the axial force effect within the framework of Eringen’ s nonlocal elasticity theory, where the governing equations of motion are obtained using Hamilton’ s principle. The superiority of the studied non-local continuum model to its local counterpart is to consider the effect of size on the mechanical behavior of the structure. The results from a natural frequency analysis are obtained for different conditions such as the effect of size and aspect ratio, axial force, nonlocal coefficient, and change in the stiffness properties of the surrounding elastic medium by using the Navier-type solution for simply supported boundary conditions. Given that in a double-layered graphene sheet, the system has an in-phase vibrational mode and anti-phase vibrational mode with 180-degrees phase difference, the effect of van der Waals force on both vibrational modes is attempted to be investigated and it is shown that the van der Waals force has no effect on in-phase vibrational mode and by increasing it, the anti-phase frequency increases. It is also demonstrated that the nonlocal parameter is not a constant parameter but its value depends on the size and atomic structure, like chiral and zigzag configurations, and even on the type of boundary conditions

In the current study, two-phase flow of water and air over a stepped spillway is probed in the form of a two-dimensional incompressible viscous flow. A novel numerical approach is used for the numerical simulation which is a combination of two models: volume of fluid (VOF) which uses an interface tracking algorithm for the simulation of the two-phase flow and two-fluid model which is based on time and space averaged equations and cannot track the interface explicitly. The most important issue in the introduced approach is to couple the two basic methods and select a proper criterion for status change between two basic methods. The latter criterion is based on an approximation from local distribution of the interface at each cell. In the hybrid method. In order to investigate the aeration effect in the stepped spillway, the air suction is generated by designing some holes at the upper edge of the steps and considering atmosphere pressure for these areas. The obtained results divulge the amount of dispersion is low at the beginning part of the step and also the hybrid model take more advantages from VOF, while in the lower steps where the flow disperses two-fluid model has hegemony. The results are compared in the form of pressure contours and streamlines as well as volume fraction counters. The comparison shows that the results of the proposed method is closer to the experimental results with respect to each of the basic model.

Today, the use of articulated long vehicles is surging. The main reasons for tendency of utilizing these vehicles is use of less tractor unit fitted to carry two or more trailers. In other words, in order to carry the same amount of goods, instead of using some tractor semi-trailers, we can make use of fewer articulated long vehicles. Reduction of fuel consumption, a significant decrease in the production of greenhouse gasses as well as using less manpower to direct the vehicle to carry the same load which is related to typical articulated vehicle is of other advantages of long articulated vehicles. The major problems of these vehicles are poor maneuverability at low speed and inappropriate lateral performance at high speed, which would lead to crashes and financial damages. Hence, a control system is required for enhancing the safety of these vehicles, improving the performance of long vehicles and preventing from being unstable. In this study, after mining and verifying the dynamic model, a new control method based on a combination of active disturbance rejection control and backstepping sliding mode control for adjusting lateral dynamic of articulated long vehicles has been utilized. The results portray the superiority of this new method than LQR and sliding mode controllers.