Modares Mechanical Engineering
Year:2016 | Volume:15 | Issue:10|Papers Count:40

Fire spread from one body to another in a road tunnel is investigated in this study, with respect to the phenomena and the physical concept. Fire Dynamics Simulator will be used as a CFD tool. Two wood boxes representing cars are modeled in a 40m long tunnel with longitudinal ventilation and fire transmission from one to another is considered. Ignition temperature is assigned to the second box surface as the ignition start condition. Indeed, ignition start of the second box depends on its temperature rise to a certain value that is extracted from experimental data. At each case, ignition time of the second box is captured. Furthermore, fire spread phenomena is considered quantitatively and qualitatively. The results show that increase of ventilation velocity causes first an increment and then a decrease in ignition time, due to both cooling and smoke plume inclination effects. Also, with increasing the distance, ignition time increment rate is faster at low HRRs. In addition, the results show that the tunnel height reduction has stronger effect on ignition time for lower HRRs. Finally, because of forced ventilation dominance in high ventilation velocities, no noticeable influence on ignition time is observed by changing the tunnel slope. To confirm accuracy of the numerical model, validation with experiments will be presented too.

This paper presents a trajectory controller for a Hovering type Autonomous Underwater (HAUV) Vehicle to meet the demands of in-water ship hull inspection. Accomplishing this task can just be done by a vehicle that has all special requirements like high maneuverability, precise controllability and especially, Hovering Capability. Utility of such vehicle causes increasing precision, saving time and money and less health hazard for divers. Thrusters' configuration in terms of the number of thrusters, position and the thrust direction of each thruster is presented to provide the most suitable formation in terms of less energy consumption, reduced complexity of control strategies and controlling the most degrees of freedom. In this paper, roll degree of freedom is just constrained. The controller that is demonstrated was designed based on the linear dynamic model and then applied to the non-linear model to validate the controller's practicality. This controller consists of 3 different loops, one for horizontal plane, another for the vertical plane, both were designed in state space and the last one is a PID controller which is developed to control the forward speed. In the next step, the robustness of the controller is investigated in the presence of underwater disturbance and uncertainty of the hydrodynamic coefficients. State feedback controllers have advantages such as being suitable for non-linear models, useful for MIMO system and simplicity in application development.

Metal bipolar plates are key components in fuel cells, which are considered to be the best alternative to replace graphite plates. Material selection in bipolar plates depends on its weight and corrosion resistance. Metallic bipolar plate can be considered the best alternative to graphite and composite plates. One of the new processes in order to produce this plate is gas blow forming process. In this study, forming of AA8111 bipolar plates with 200 mm thickness in concave groove dies is investigated by gas blow forming process at various pressures (20, 30 and40 bar) and temperatures (300 and 400oC). The filling percentage of die at various wall angles and depth to width ratios are examined. According to the dimension of channels, maximum and minimum thinning percentage at high temperature and pressure are investigated. Results show that at wall angle of a= 0, and the depth to width ratio of h/w=0.5, rupture occurs at pressure of 20bar and at temperature of 300oC and at pressures of 20 and 40 bar at temperature of 400oC. The best channel filling with lowest thinning obtained at a= 15 and h/w=0.5.

The aerodynamic characteristics of nine configurations of supersonic continuous deflectable nose guided missiles have been investigated. Then the optimized geometry is achieved based on the maneuverability from aerodynamic and flight dynamic point of view. The studied configurations consist of a spherical nose tip, a tangent ogive, one set of stabilizing tail fins and a cylindrical body whose mid-section is flexible to form an arc of a circle. So the cylindrical body consists of a fixed part in the vicinity of nose, middle flexible part and main body with stabilizers. The effects of fixed length and flexible length parameters on the aerodynamic and flight dynamics of guided missile have been studied. A code has been developed to solve full Navier-Stokes equations using finite volume and modified Baldwin-Lomax turbulence model. Multi-block technique is also used to solve main body and fin parts flow field. Further, a 3 degree of freedom code has been developed to compare planar flight dynamic of missiles. It is found that missiles with bigger lengths for fix and flexible parts show more aerodynamic maneuverability, but drag force grows concurrently. Flight dynamic analysis shows that drag effect is negligible and aerodynamic maneuverability analysis is compatible with flight maneuverability.

In this research two-phase slug flow regime in a T-junction branching divider is examined in two regular and irregular groups. Simulation is accomplished by OpenFOAM™ open source software. Simulation uses single fluid with volume of fluid (VOF) method to follow gas-liquid two-phase flow interface. Constant velocity boundary condition for inlet, constant pressure for outlet boundaries and no slip boundary condition are considered for fixed walls. Since slug flow regimes are one of the most complex two-phase flow regimes whose behavior could result in serious damages to the downward equipment, the present research concentrates on the examination of slug flow behavior in the downstream of the T-junction. This study has concluded that using T junction eliminates flow fluctuation so the pressure and air velocity values decrease. Although the inlet of the vertical branch with cross section of 5´5 cm2 is not fully effective in decreasing upward slugs, with the size of the inlet vertical side-branch from 5´5 cm2 to 10´5 cm2 and 20´5 cm2, pressure value of two-phase flow in the whole duct decreases. The consequences are the slug flow decreases in downstream but the plug flow rises which means the objectives of the research have been accomplished. To verify the numerical results, comparison was made with the well justified previous works. The agreement was encouraging.

In this study, an application of support vector machines is presented for fouling detection and estimating the amount of deposit layer development and tube blockage percentage at the radiation section of the crude oil preheat furnace. Crude oil preheat furnaces are the main elements in processing crude oil in distillation towers, which always suffer from fouling and its consequent risks. In order to predict fouling inside the tubes, first by considering independent input parameters effecting the furnace performance and by using a dynamic model of a particular furnace, the behaviors of the furnace in unusual conditions were simulated. The effects of fouling type and its location inside the tubes were considered on the thermal performances and pressure drops of the furnace. In the second part, based on the different fouling scenarios, a fouling detection mechanism was designed. The operational conditions such as pressure drop inside the tubes, temperatures of the tubes and temperatures of the crude oil were employed for fouling detection and evaluating the thickness of deposits. The obtained results indicated the accuracy and feasibility of the proposed approach.

This paper deals with the problem of safe grasping of an object. According to robot maneuvers during movement, the slipping or falling of the objects is possible. Here, an adaptive back stepping control method is used for controlling of slipping and tracking of desirable paths. First, the robot dynamics of grasping of an object including mechanical arm with three rotational joints, one prismatic joint, jaw gripper as well as dynamic of the electrical actuators is derived. Then, back stepping technique, which is a systematic approach based on Lyaponov theory, is applied for this nonlinear system. Because of existence of different uncertainties in this system such as mass and inertia of robot and object mass, it is required to design a controller to be able to cope with these uncertainties. Accordingly, a stable controller using adaptive back stepping control methodology is also designed to estimate of these parameters’ uncertainties. Stability analysis is provided based on Lyapunov theory. Simulations are carried out to evaluate the performance of the proposed controller. Results show the effectiveness of the proposed control method.

In this paper, by applying a new programming mode, thermo mechanical behavior of activated composite with shape memory alloy fiber is extracted subjected to cyclic off axis loading using a 3D analytical micromechanical model. Object-orientation and its applied principles are implemented on the micromechanical model and response of the composite is determined by Newton-Raphson nonlinear numerical solution method at different thermal interval. In order to achieve an optimal response, a factor such as convergence coefficient in the Newton -Raphson nonlinear solution method is employed. Representative volume element of the composite consists of two-phases including shape memory alloy fiber and metal matrix. behavior of the metallic matrix is considered as viscoplastic while shape memory alloys is assumed nonlinear inelastic based on Lagoudas model which is able to model phase transformation and super elastic behavior of the shape memory alloys. Moreover, arrangement of fibers within the matrix is considered randomly. Thermo mechanical responses of composite at different temperature ranges are investigated to display the shape memory effect and super elasticity properties of shape memory fiber. In this regard, at the first, the composite system is exposed to cyclic mechanical loading and unloading and then exposed to thermal loading. Shape memory effect, property of shape memory wire and composite are compared and the effects of forces within the active composite induced via axially constraining the composite are investigated. Furthermore, the effect of fiber orientation is illustrated. Comparison between the present research results and previous available researches shows good agreement.

The sensitivity of the moving platform of parallel mechanisms to the uncertainties in the design and control stages is of paramount importance. The mechanism has to be designed such that the negative effect of the foregoing errors is minimized. The latter issue has encouraged many researchers to derive and propose relevant indices that are responsible for outputting a metric representing the kinetostatic performance of parallel mechanisms. Most of such indices entail severe drawbacks, leading to physically inapplicable interpretation, which was considerably alleviated by the emergence of kinematic sensitivity. Nevertheless, none of the studies heretofore has investigated the influence of the uncertainties in the passive joints on the kinetostatic performance. In other words, the assumption has always been that the aforementioned errors are negligible. This paper proposes a novel formulation for the kinematic sensitivity index, which, apart from that of the active joints, takes the effect of the uncertainties in the passive joints into account and brings about the advantage that the mechanism can be optimized and improved in terms of kinetostatic performance, together with the workspace. The formulation, for the sake of illustration and verification, is also applied to the 4-bar linkage and 3-RPR parallel mechanisms, as well as the Tripteron robot. The results of the implementation of the proposed kinematic sensitivity index, which takes the effect of the uncertainties in the passive joints into account, show that the values associated with the case-studies considered in this paper fall within the intervals 1-2.4, 0.1-0.9 and 0.6-2.2, respectively.

Ship maneuvering in calm water and waves is an important topic to avoid collisions and broaching, therefore reliable ship maneuvering simulations are required for incident analysis and prevention. The maneuverability of planing crafts has been the subject of many research projects during the last few decades. To assess the maneuverability of planing crafts at the early design stage, reliable simulation models are required. Traditionally, these tools have used empiric descriptions of the forces and moments on the planing craft’s hull. However, today new numerical modeling techniques are available, enabling more reliable predictions of the maneuvering behaviour of planing crafts. Ship maneuvering performance evaluation is essential in primary design stages. Ship maneuvering calculations, horizontal plane motion control and development of maneuvering simulators require a mathematical description of ship maneuvering. In recent years, different mathematical models have been suggested for maneuvering of displacement vessels that are capable of estimating vessel maneuvers with acceptable precision. But simulation of planing craft maneuverability through mathematical model is not common yet and is the subject of future research. In this paper different maneuvers are executed through the mathematical model. Then the mathematical model is solved and different maneuvers are simulated. Simulations are validated by model tests. Finally, the influence of rudder angle on maneuverability of planing ship is studied. Difference between simulation results and experimental is less than ten percent. At the end of this paper the effect of the rudder dimension on the tactical diameter of planing ship in turning maneuvering is evaluated.

The unbalancing is a destructive phenomenon and a major cause of undesired vibrations in rotating machinery. One of the new methods used to reduce the imbalance is the implementation of automatic dynamic ball balancer. In previous studies the dynamic behavior of automatic ball balancer has been investigated. These studies indicate numerous advantages of automatic ball balancer. However, the traditional automatic ball balancer has two major deficiencies: First, the rotor vibration amplitude is larger than that of a rotor without an automatic ball balancer in speeds below the first critical speed and, the second deficiency is that it has a limited stable region of the perfect balancing configuration. In this paper, a new design of a three-ball automatic balancer is introduced. The governing equations of motion are derived using the Lagrange's equations, and the balanced stable region is obtained. It is shown that this type of automatic ball balancer can prevent the vibrations of the rotor from increasing at the speed range below the first critical speed. Moreover, the new type of balancer increases the balance stable region of the system. Reducing the vibration amplitude in the mentioned range causes the lifetime of the system to be increased. Moreover, increasing the balanced stable region allows the new design of balancer to balance the systems with a wider range of parameters.

In the seismic vibrations of large and widely used structures such as dams and bridges, as well as the forced vibration tests with artificial vibrators, the dominant excitation forces are generally measurable. Not applying the inputs in the system identification is one of the main reasons for error generation in the operational modal analysis (OMA), so the non-structural dynamic characteristics due to the input excitations can be reduced by applying these inputs in the dynamic model of the system. In this paper, a special modal analysis is presented in the subspace methods field that filters the excitation effect of the measured input forces from the test data using orthogonal decomposition technique and identifies the stochastic system with an optimal subspace method based on Canonical Correlation Analysis. To evaluate the proposed method, the seismic data from the Pacoima dam and forced vibration test results of the Alamosa Canyon Bridge have been used. Non-structural and noisy poles removal, and increased accuracy of the derived modal properties, specially damping ratios, can be mentioned as the important results of the study. At Pacoima dam, the SSI-Data method identifies four non-structural modes, while the proposed method derived the first two modes just like the previous results without any noise. In addition, the damping ratios of the Alamosa Bridge are derived according to the Hammer test, which were not obtained in the previous investigations. At Pacoima Dam the related damping ratios have significant association with force vibration tests.

Due to instability and specific configuration of tailless aircraft, there should be a controller with capability of stabilizing the aircraft in various maneuvers and flight conditions and also to have desired robustness against different parametric and non-parametric uncertainties. In this paper, we design a multi input-multi output combined model-reference adaptive controller for a tailless aircraft. Coordinated turn is itself an unstable maneuver. The addition of the instability of this maneuver and the instability of a tailless aircraft causes a highly unstable situation. Combined model-reference adaptive control benefits the aggregation of the tracking error and prediction error. Combining these two sources of errors alleviates the transient response characteristics, and a combined model-reference adaptive controller has better performance compared to the classical model-reference adaptive controllers (with tracking error as the only source of parameter estimation error), and this property could be useful in highly unstable systems like tailless aircraft. Here, after extracting the equations of motion of an aircraft and exerting the conditions of coordinated turn maneuver, we design a combined model-reference adaptive controller for a tailless aircraft. The simulation results show accuracy of the designed controller in stabilizing the aircraft during the coordinated turn maneuver and its robustness against uncertainties.

Dynamics of an electromechanical energy harvesting cantilever beam deposited by two piezoelectric layers throughout the entire length have been studied. Two different output circuit configurations including parallel and series connections have been investigated. The free and forced vibration problems are studied by discretizing the motion equation and numerically solving the resultant along with the governing electrical equation. The energy conservation law for the proposed electromechanical energy harvesting device has been examined and accordingly verified. The behavior of the energy harvester subjected to various external load resistances was studied and it was concluded that in the absence of mechanical viscous damping, the system exhibited damped response which was attributed to the energy consumption throughout the output circuit. It was proved that as the external load resistance increases, until the special load resistance the attenuation rate of the response amplitude and accordingly the harvested voltage also increase, and for higher load resistance it was reverse. The amount of harvested power for both parallel and series output circuit configurations were examined and it was indicated that in some load resistances in series configuration the harvested voltage compared with that of the parallel connection is considerably higher; however, the harvested current was lower than that of the parallel connection.

In the present study, thermal buckling analysis of functionally graded carbon nanotube reinforced composite (FG-CNTRC) conical shells is presented. The effective material properties of FGCNTRCs are determined using the extended rule of mixture. By employing the Hamilton’s principle and based on first-order shear deformation theory and Donnell strain-displacement relations, the governing equations are obtained. The membrane solution of linear equilibrium equations is considered to obtain the pre-buckling force resultants. Using the generalized differential quadrature method in axial direction and periodic differential operators in circumferential direction, the stability equations are discretized and the critical buckling temperature difference of shell is obtained. The accuracy of the present work is first validated by the results given in the literature and then the impacts of involved parameters such as volume fractions and types of distributions of carbon nanotubes, boundary conditions and geometrical parameters on thermal buckling of functionally graded Nano composite conical shell are investigated. The results indicate that the values of volume fractions and types of distributions of carbon nanotubes along the thickness direction play an important role on thermal instability of FG-CNTRC conical shells.

In critical situations such as floods and earthquakes, the relief forces require a refrigerator for pharmaceuticals and vaccines which can operate without electrical energy and instead, use alternative energies such as solar energy, vehicle exhaust energy, wind energy, etc. In this paper, modeling of a refrigerator with an adsorption refrigeration cycle using activated carbon/methanol as adsorbent/adsorbate pair which utilizes two sources of energy, solar energy and vehicle exhaust energy is presented in MATLAB. The solar refrigeration cycle includes a collector with area of 1m2 and the exhaust gas cycle includes a heat exchanger with temperature difference of 100oC between its inlet and outlet gases. Modeling results represent the temperature profile in adsorbent bed, evaporator and condenser. Moreover, the pressure profile, overall heat transfer coefficient of collector and adsorbent bed, concentration and solar radiation are reported. The results show coefficient of performance of 0.549 and solar coefficient of performance of 0.200 for solar adsorption refrigeration and coefficient of performance of 0.561 with specific cooling power of 2.478 for exhaust heat adsorption refrigeration. These results reveal the good performance of the proposed model in the climate of Iran.

In this research the effect of the screw angle and the depth of the channel were examined on the flow rate of an incompressible Newtonian isothermal and a non-Newtonian fluid flow in a single screw extruder. In the present study only drag force was considered rather than pressure drop. For this purpose, the extruder channel was assumed to be a cubic and spiral channel. Accordingly the Newtonian flow was simulated by Fluent software package and the results were compared with analytical solution in several angles. Then one step from the shallow spiral channel was examined and the results were compared with analytical solution in different angles and also at low Reynolds numbers. Hence, the obtained results reveal the range of validity for the analytical solution at different Reynolds numbers. As the results show, at low Reynolds numbers, up to 10, and the ratio of channel depth to diameter, less than 0.2, numerical and analytical results are the same for Newtonian fluids. Identically, in this range the analytical solution can be used for screw design, calculation of the maximum flow rate, the evaluation of the optimum angle, etc. The results of the study of non-Newtonian fluid showed that the flow rate at low screw angles for non-Newtonian fluids was higher than the Newtonian cases and at high angles, were smaller.

In recent years, many researches have investigated nanofluids pool boiling and reported some contradictory results. In this study, the pool boiling heat transfer of water-alumina and TiO2-water nanofluids at saturated temperature was investigated experimentally. The experiments were conducted to investigate the impact of concentration and type of nanofluid on the pool boiling heat transfer of brass surface. Water-alumina and TiO2-water nanofluids with volumetric concentration of 0.0025-1% and 0.0025, 0.01, 0.25% were used, respectively. An experimental setup with a cylindrical heated test section made of brass and surface roughness of 0.2mm was designed and fabricated. The experimental results showed that, the heat transfer decreases as the nanoparticles are added into the pure water base fluid. At a constant heat flux, the heat transfer coefficient decreases as the alumina volumetric concentration increments from 0.0025 to 0.01% and then increases for further addition from 0.01 to 1%. The TiO2-water nanofluids performance with respect to the water-alumina nanofluids was not very promising. That means, the boiling heat transfer decreases while the boiling surface temperature increases at a constant heat flux.

Free vibration analysis of a cracked rotating multi-span Timoshenko beam is studied in this article to determine the natural frequencies and mode shapes of this beam. First, the relationships between each two segments are obtained by considering the compatibility requirements in the frame angles and in the cracks. To determine the transformed compatibility requirements, the boundary conditions, and the vibrational equations, the so-called differential transform method (DTM) is used. Then, these equations are performed to determine the natural frequencies. The mode shapes of the beam are determined by using the inverse of differential transform method. The results have been validated against those obtained from Abaqus software for a rotating multispan beam and the ones obtained from transfer matrix method for a non-rotating case in which an appropriate agreement is observed. Finally, the effects of the angle of break, the rotational speed, and the crack location on the natural frequencies are investigated. It is shown that the natural frequencies will be increased by increasing the rotational speed. Also, it is seen that the first natural frequency will be increased by moving the crack location from the cantilever support to free support and the variations of other frequencies are dependent on the crack distance to the vibrational nodes. The validation results show the accuracy of DTM in the process of studying the free vibration of this problem.

This paper presents a numerical study on melting behavior of phase change material (PCM) in a horizontal double pipe heat exchanger. The shell side is filled with RT50 as PCM and water is used as heat transfer fluid (HTF) which flows through inner tube. The aim of the study is to investigate the effect of eccentricity as a geometrical parameter on melting behavior of PCM through downward movement of the inner tube. In addition, effective flow parameters such as mass flow rate and HTF inlet temperature are investigated on thermal storage performance. Enthalpy porosity method is used for modeling phase change process. At the beginning of melting process, conduction is dominant heat transfer mechanism and over time passing natural convection will be the main heat transfer mechanism. Results show that by increasing eccentricity, the dominant area for the natural convection expands and phase front penetration velocity increases which leads to considerable decrease in melting time. By increasing inlet temperature from 70oC to 75oC and 80oC, total melting time decreases up to 16% and 27% respectively. Although by Increasing Reynolds number from 1000 to 1500 and 2000, total melting time only decreases to 1% and 3%, respectively. These results show that Stefan number influences melting time more noticeable than Reynolds number.

Fracture of femur is considered as one of the most significant causes of disability and death, especially among the elderly. Therefore, there is a global effort towards noninvasive assessment of the femoral fractures. This study was aimed at investigation of the mechanical behavior of human femur subjected to various loading orientations, under the two categories of high-stiffness (HS) and low-stiffness (LS) loading conditions. The experimental and computational analysis of deformation and fracture patterns were carried out using the QCT images and finite element analysis. The predictions of the force and fracture pattern of the HS and LS specimens were performed using linear and nonlinear finite element analyses, respectively. Also, the cohesive zone model (CZM) was used to simulate the damage initiation and propagation in the finite element analysis of latter specimens. Comparison between the results of the numerical analysis and the experimentation showed successful simulation and prediction of fracture force of human femur under various loading orientations.

Consumption of cutting fluids imposes high costs on industry. These cutting fluids contaminate the environment and are harmful to human health. Minimum quantity lubrication technique (MQL) is a new approach to reduction of cutting fluids consumption, improving efficiency of cutting fluid at machining zone and using harmless fluids. However, this technique faces cooling limitation in grinding. The purpose of this study is an accurate study of heat transfer mechanism in minimum quantity lubrication technique by its temperature numerical simulation and improving the cooling ability of its air jet by using a simple and inexpensive vortex tube. For this purpose, a system was designed and manufactured to measure the convection heat transfer coefficient of different conditions of MQL environments. The result of convection heat transfer tests shows 95% share of compressed air in heat transfer and also air pressure is a more important factor than temperature in cooling process. The result of temperature numerical simulation shows that by increasing pressure, the increasing rate of convection heat transfer coefficient decreases; also, the cooling ability temperature of the vortex tube at low thermal power is tangible. In grinding of soft steel, the minimum quantity lubrication technique with cold air (CAMQL) in comparison with other methods leads to significant reduction of tangential grinding force and friction coefficient, but in general, except in the case of optimum condition which has the highest heat transfer coefficient, surface finish is worse, which is related to low heat transfer coefficient of gases at low pressures.

In the first part of this study the methods of direct and indirect entering the effect of induced velocity in blade element theory to achieve lift force in hover flight of Drosophila flapping insect are investigated. Then a new algorithm for Induced velocity correction based on Rankin-Froude jet theory and direct method is presented. The results of both previous and new methods to aerodynamic simulation of this insect in hovering flight with combined flapping and pitching angles were compared with published experimental results. The results of this comparison indicate one of the models based on the indirect method as the best way to predict the experimental results. In the second part of this work, the sensitivity of the instantaneous and mean force, produced by insect modeled wing, is examined with change in six wing important motion parameters. These parameters include: flapping frequency, phase difference between flapping and pitching angle, flapping and pitching amplitudes and flapping and pitching variations with respect to time in flapping cycle. The results show that with increasing frequency and flapping amplitude lift gradually increases. Also, range of phase difference percentage between flapping and pitching angle that leads to maximum lift of the wings is introduced. Results also show that sinusoidal variation of flapping angle in the cycle has more lifts than rectangular variation.

Thermal creep is often associated with the flowing of a rarefied gas via the effect of temperature difference in solid boundaries. Recently the feasibility of such flow in dense fluids has become a challenge. This paper deals with simulating the thermal creep flow in liquids confined in nanotubes. The investigations are carried out by molecular dynamics simulation method. The goal of this work is to provide a clean picture of the thermal creep phenomenon mechanism in liquids. Simulation results show the existence of such flow in liquids in nanotubes. The thermal creep effect is stronger in nanotubes with narrower cross sections. Molecular data provided by the simulations shows there is a fluid layering phenomenon near the solid wall. The fluid layering together with the wall temperature gradient develops a pressure gradient near the wall. This pressure gradient acts as a planar force and is assumed to be responsible for the thermal creep effect. This force causes the fluid to flow toward the hot side of the tube. The mechanism of thermal creep phenomena is justified by the use of molecular principles and molecular data which are obtained from the molecular dynamics simulations.

In this paper, dynamic stability of a laminated composite beam subjected to a tip follower force is investigated. Using elementary theory of bending, Euler-Bernoulli beam theory and Classical Lamination Theory (CLT), bending moment of laminated composite beam is calculated with respect to it’s extensional, bending and bending-extensional coupling stiffness matrices, A, B and D, and dynamic stability equation of laminated beam is established. Due to similarity between this equation and isotropic stability equation, as an assumption, isotropic beam boundary conditions are used for composite beam. Cantilever- free boundary conditions are used and a closed form solution is established. Flutter instability problems for symmetric and un-symmetric laminated beams are solved by this method and results are compared with finite element results in literatures. Considering the simplicity of the present method, results show good agreement with the finite element method. Finally dynamic stability behavior of laminates with different stacking sequences are investigated by present method and effect of different parameters such as fiber orientation, number of layers, and stacking sequence, on the flutter load and corresponding frequency of symmetric and un -symmetric laminates are investigated.

In the current study, the motion and deformation of an elastic membrane in a two-dimensional channel with and without a groove is simulated using a combined lattice Boltzmann-immersed boundary method. The lattice Boltzmann method is used to solve the fluid flow equations and the immersed boundary method is used to incorporate the fluid-membrane interaction. The elastic membrane is considered as a flexible boundary immersed in the flow domain. In the immersed boundary method, the membrane is represented in the Lagrangian coordinates while the fluid domain is discretized on a uniform fixed Eulerian grid. The interaction between the fluid and the membrane is modeled using Dirac delta function. The effects of no-slip boundary condition are enforced by addition of a forcing term to the lattice Boltzmann equation. Depending on the flow rate (or Reynolds number), the initial location and stiffness of the elastic membrane, the size of the groove, the membrane only rotates inside the groove or the flow moves it out of the groove. The results are presented in terms of flow velocity and pressure fields and membrane configuration at different times. Comparison between the present results and the available numerical and experimental ones shows good agreement between them.

This study is concerned with optimizing the daily operation of a solar power plant equipped with thermal energy storage system (TES). The modeling is performed by solving a set of non-linear governing equations and is verified through comparison with the literature. "Maximum production period" and "maximum revenue" constitute the objectives of the optimization study which are first considered individually (as two single-objective problems) and are then considered simultaneously (as a multi-objective problem). Genetic Algorithm (GA) is employed as the optimization tool. The results of the first objective (maximum production period) shows a 7 hour increase in the daily production time as a result of employing the TES system. This occurred through saving energy during times of high solar radiation and using the stored energy for electricity generation during times of low or zero solar radiation. The results of the second objective (maximum revenue) indicate 13.5% increase in the produced profit as a result of employing the TES system. This improvement was resulted from saving energy during times of low electricity price and using the stored energy for maximum electricity generation during times of high electricity price. Finally, in the multi-objective study, 5 hour increase in the production period and 8.1% increase in the revenue were simultaneously obtained as a result of a proper tradeoff between the two objectives.

In this paper, a new type of iterative learning control systems with fractional order known as iterative learning control with fractional order derivative and iterative learning control with fractional proportional–derivative for linearized systems of single-link robot arm is introduced. First order derivative of classic Arimoto is used for tracking error in updating law of derivative iterative learning control. The suggested method in this paper implements tracking error for updating control law of iterative learning of fractional order. For the first time, nonlinear robot system is linearized by input feedback linearization. Then, convergence analysis of iterative learning control law of type PDa is studied. In the next step, we define criteria for parameters optimization of proposed controller by using Biogeography-based optimization algorithm. Both updating laws of fractional order iterative learning control (Da-type ILC and PDa-type ILC) are applied on linearized robot arm and performance of both controllers for different value of a is presented. For improving the performance of closed loop system, coefficient of fractional order iterative learning control (proportional kp and derivative kD coefficients and a) is optimized by BBO algorithm. Proposed iterative learning control is compared with common type of system.

In the present article, an improved Learning Classifier System (LCS) is proposed to control the balance of a moving unmanned bicycle. A significant characteristic of learning classifier systems is that they can learn through a set of system actions in the real world (similar to intelligent creatures) while no dynamic model of the system is needed. Contrary to studies reported in the literature where action domain of the controller is discrete and accordingly such controller cannot be used in real world applications, in the present study efficacy of the classifier system is enhanced by definition of continuous domain for the outputs, and then is used to control the balance of unmanned bicycle. A scheme based upon fuzzy membership functions is proposed which makes it possible for the domain of actions to be continuous. The proposed LCS features a dynamic reward assignment mechanism which is invented to cope with the bicycle’s delayed response due to its mass inertias. This allows the rapid calculation of the reward and hence enables the controller to be used in such real time applications as the balance control of unmanned vehicles. A standard 2 degree of freedom (2-DOF) bicycle model is employed to demonstrate the efficiency of the enhanced LCS. Simulation results show that the proposed classifier system outperforms traditional classifier system as well as some of the more common balance-control strategies reported in the literature.

In this paper, a useful method proposed for aerodynamic design of Megawatt wind turbine blade based on Blade Element Momentum (BEM) theory. In this method first a preliminary design is done based on the ideal BEM and then a method have been offered for geometric modifications to approximate the geometry of the blade to a real and functionally one. The advantage of this method is that needed few design parameters that simplify the design procedure, however its results are in good agreement with 5MW NREL reference wind turbine assumed as validation case and show that with use of this method can achieve a good aerodynamic design, Then the twist angle has been optimized using Genetic algorithm and Bezier curve with annual energy production (AEP) as the goal function. At the end, a 2.5 MW wind turbine has been design based on this method with considering the Lootak site specifications in province of Sistan and Baloochestan. Then 3D model of the blade has been made and CFD simulation applied on that for showing the designed turbine operation in real conditions and comparison with BEM method. The results show that is acceptable compatibility between two analytical methods.

Drying of porous materials is a critical step in the production of many products such as ceramics, brick and tile. Quality of dried product is significantly influenced by drying processes. The aim of the present work is modeling of convection drying of a ceramic by using diffusion model. Material properties changes such as Young's modulus and shrinkage factor to moisture content are considered in simulation. Both two and three dimensional configurations have been investigated. The model is solved numerically by a finite element method. A significant difference was observed between the results obtained for the two different configurations, particularly in the intensity of the drying-induced stresses. Validation of results is achieved by comparing the numerical and experimental results. The effect of Young’s modulus variation has been investigated. It was observed that drying-induced stresses are highly affected by Young's modulus variations. According to the results, none of the simulation methods, can be regarded as a safer method in crack prediction. The changes in Young's modulus has no effect on the location of maximum stress, however, its timing is delayed.

In this research, the effects of flow rate and temperature of supply air on the performance of a bed-based task/ambient air conditioning system (TAC) have been investigated. For this reason, a bed-based task/ambient air conditioning system including a bed, a supply air inlet on the top of the occupant's head and a return air outlet under the bed have been considered and for the mentioned conditions, the equations of flow, energy and thermal comfort have been solved by OpenFoam numerical solver. Also, the thermal comfort conditions, local thermal discomfort and energy utilization coefficient have been evaluated in the present study. The results show that the performance of the mentioned system significantly depends on the supply air temperature and flow rate. So, the low supply air flow rates may cause non-uniform temperature and velocity distributions which leads to unpleasant thermal comfort conditions. Also, in order to achieve the benefits of TAC systems, utilizing the high supply air flow rates must be avoided because in high flow rates a wide area of the room is affected by supply air instead of the bed zone. Also, the results indicate that the energy utilization coefficient decreases with supply air flow rate increment. Therefore, this coefficient has reached to less than 1.5 in 120 lit/s air flow rate that demonstrate the low advantage of using TAC systems in high supply air flow rates.

Computer-aided process planning (CAPP) is a bridge for integrating computer-aided design (CAD) and computer-aided manufacturing (CAM). One of the basic computer-aided process planning tasks is sequencing of machining features. Sequencing of machining features is determined based on technical and geometrical rules. In this paper, the technical rules, geometrical rules and sequencing of machining features method were discussed. At first, some of the technical rules were pointed. Then, the geometrical interactions were studied and two new geometrical rules were introduced for sequencing the machining features having geometrical interaction. These rules can yield unique results and they are identified easily by the computer systems. Also, an algorithm was introduced for automated application of these geometrical rules in computer systems. The conflict between the technical and geometrical rules that may occur in some cases was studied. This conflict must be considered in the sequencing of machining features methods. Finally, an algorithm was introduced for sequencing of machining features based on permutation. In this algorithm the technical and geometric rules were applied separately and step by step. Any conflict between technical and geometrical rules could be detected automatically in this algorithm. Algorithms were programmed and verified in PythonOCC.

In this paper, non-equilibrium molecular dynamic simulation has been employed to study the effect of wall interfacial properties and temperature of system on the hydrodynamics and heat transfer of water molecules in a nanochannel. The charges and Lennard-Jones potential are used to model the interactions between particles. The external forces are applied to the mass center of every water molecule in the x direction to create its flow and the thermal and hydrodynamics behavior of the water molecules was then analyzed. To construct the wall pore model, two silicon solid surfaces were used and the temperature of system was controlled by utilizing Nose-Hoover thermostat. The interaction strength (esi-w) between wall atoms and water's oxygen atoms were adjusted to indicate different surface wettability or wall–fluid interaction. The higher value of (esi-w) causes the higher hydrophilic wall interface. The simulation results showed that the interaction strength (esi-w) and temperature of system are important in determining the Nano rheology of the Nano channel and flow resistance of the confined water. The drag resistance at the solid–fluid interface will increase with increasing the hydrophilicity of walls (esi-w). Also, the heat dissipation of system will increase with increasing the drag resistance at the solid–fluid interface and as a result, the heat flux of system will decrease.

In present study, the impact of a single bubble on an inclined wall and its movement is investigated by applying volume of fluid method (VOF) in OpenFOAM open source cfd package using a solver called interFoam. Both phases are incompressible and surface tension between the two phases is estimated by CSF method. The effect of some parameters such as contact angle, wall slope and Bond and Morton dimensionless numbers on bubble shapes and velocity are studied. The numerical results show bubble velocity along wall increases with the increase of wall slope angle. Three bubble regimes are recognized and introduced in this study named: sliding, bouncing, and zigzagging based on wall slope. The bubble regime changes from sliding to bouncing when wall slope changes from 30 to 40 degrees. In constant Morton number, increment of Bond number increases both velocity and amplitude of fluctuations. In addition, an increment of Morton number in constant Bond number decreases velocity and amplitude of fluctuations. Moreover, by increment of Morton number, the bubble motion will change from an accelerating motion to a constant velocity condition.

In the present study, the pressure equation associated with two-phase, incompressible and immiscible flow in porous media is solved by the multi-scale finite volume method (MsFV) for 2D problems. The MsFV method along with its main source of errors is mathematically and physically described. Associated with the computational grids used in the MsFV method, a set of two-scale isotropic permeability domains is designed. These permeability domains are produced to show how and where the errors are initiated in the pressure domain of the MsFV method. For each permeability domain, the pressure and velocity solutions obtained by the multi-scale method are compared with those of the standard finite volume method (as the reference solutions). The numerical results indicate that the MsFV method is sensitive to the fine cells with low permeability data located at the faces and corners of the dual grid blocks. Most errors are observed when the corners of the dual blocks are located on fine cells with low permeability value. In addition, by introducing the adjusted boundary condition, the effects of the permeability averaging for the edges and corners of the dual blocks on the MsFV errors are also investigated.