Heat and Mass Transfer
Isa Ahmadi
Abstract
The non-Fourier effect in heat conduction is important in strong thermal environments and thermal shock problems. Generally, commercial FE codes are not available for analysis of non-Fourier heat conduction. In this study, a meshless formulation is presented for the analysis of the ...
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The non-Fourier effect in heat conduction is important in strong thermal environments and thermal shock problems. Generally, commercial FE codes are not available for analysis of non-Fourier heat conduction. In this study, a meshless formulation is presented for the analysis of the non-Fourier heat conduction in the materials. The formulation is based on the symmetric local weak form of the second-order non-Fourier heat conduction equation in terms of the temperature. Using the local weak form of heat transfer equations in the sub-domains, the governing equation of the non-Fourier heat conduction is discretized in the space domain to the second order ordinary differential equations for the time. The discretized equations are integrated into the time domain with an appropriate finite difference method. The fictitious numerical oscillations are completely suppressed from the front of temperature waves in the presented method. An analytical series solution is developed for the non-Fourier heat transfer in one-dimensional heat transfer for special boundary conditions and the accuracy of presented numerical meshless method is validated by comparison of the results of the numerical meshless solution and the series solution. The numerical results are presented for non-Fourier heat conduction for various Vernotte numbers and boundary conditions and the results are compared with the results of the classical Fourier heat conduction.
Vibration
N. Nadirian; H. Biglari; M. A. Hamed
Abstract
The purpose of this paper is to control simply supported flexible core sandwich beam's linear vibration equipped with piezoelectric patches under different loads. The effects of external forces imposed on the sandwich beam can be reached to a minimum value by designing an appropriate controller and control ...
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The purpose of this paper is to control simply supported flexible core sandwich beam's linear vibration equipped with piezoelectric patches under different loads. The effects of external forces imposed on the sandwich beam can be reached to a minimum value by designing an appropriate controller and control the beam's vibration. Three-layer sandwich beam theory is used for analytical modeling of sandwich beam vibration. Euler-Bernoulli beam theory and linear displacement field are used for the face-sheets and the soft core, respectively. The piezoelectric stress resultants are expressed in terms of Heaviside discontinuity functions. Governing equations of motion are obtained using Hamilton’s principle. The state space equations of the system are derived from governing equations of motion, by defining suitable state variables and using Galerkin’s method. The controller is designed using linear quadratic Gaussian (LQG) technique and Kalman filter is used to estimate the state of the system. The numerical results are compared with those available in the literature. The obtained results show that the controller can play a big role toward damping out the vibration of the sandwich beam. It also shows the difference between the vibration of top face sheets and bottom face sheets because of the flexibility of the core and the situations of sensor and actuator on the top or bottom face sheets have an important role on the dynamic response of sandwich beam.
Solar Energy
H. Hoseini; R. Mehdipour
Abstract
Solar chimney power plants are plants based on solar thermal power including three parts of collector, chimney and turbine, which is able to produce electrical energy. One of the effective parameters in increasing the power production is the collector angles versus horizon. In the present study, a numerical ...
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Solar chimney power plants are plants based on solar thermal power including three parts of collector, chimney and turbine, which is able to produce electrical energy. One of the effective parameters in increasing the power production is the collector angles versus horizon. In the present study, a numerical analysis of a solar chimney power plant for different angles of the collector (divergent, convergent and horizontal type collector) is proposed. The introduced numerical model uses mathematical models of heat transfer. In this regard, effect of various angles of the three considered collectors on temperature distribution and power production of the solar chimney is evaluated. Divergent type collectors produce more power than convergent and horizontal collectors, as they produce more velocity and mass flow rates. It will be shown that by increasing the angle of divergent-type collector (keeping the inlet height constant), the power production will be increased and the output temperature will be decreased, in a way that the angle variation of 0.8 to 1 will increase the divergent type collector output power by 11 % and will decrease the output temperature by 0.78%. In the other case, when the output height is kept constant and the collector angle changes, performance of the divergent type collector is better than the other two collectors. Power production in a constant mean height is shown to be 3 times and 1.5 times more than the convergent and horizontal collectors respectively.
Fluid Mechanics
M. Mahdi; M. Shariatnia; M. Rahimi
Abstract
Microbubbles are used in ultrasound imaging, targeted drug delivery, destruction of cancerous tissues, etc. On the other hand, the demographic behaviors of small bubbles under the influence of Ultrasound have not been fully detected or studied. This study investigates the effect of the radial distribution ...
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Microbubbles are used in ultrasound imaging, targeted drug delivery, destruction of cancerous tissues, etc. On the other hand, the demographic behaviors of small bubbles under the influence of Ultrasound have not been fully detected or studied. This study investigates the effect of the radial distribution of Sonazoid microbubbles on frequency response. It is shown that the optimal subharmonic response is possible by controlling the size distribution. For this reason, the numerical simulation of the dynamic behavior of a coated microbubble is performed using MATLAB coding and the modified Rayleigh-Plesset equation. The Gaussian distribution is then applied, and the frequency response is investigated. It was shown that at a constant excitation pressure of 0.4 MPa and a standard deviation of 0.2, with increasing mean radius, the fundamental response increases. The subharmonic response increases reaches a peak value and decreases. This peak value occurs for frequencies of 4,6, and 8 MHz in the mean radius of 0.8, 1 and 1.6 μm. By increasing the frequency of excitation, it is transferred to a smaller mean radius. It is also observed that the fundamental and subharmonic responses are amplified by increasing the excitation pressure. Studies show that the optimal subharmonic response can be achieved for various applications by controlling the size distribution of microbubbles.
Optimization
Meraj Rajaee; Mina Jalali
Abstract
The solar tree is a combination of technology and art that is considered as the application of solar energy in the art of urban architecture. This study aims to combine solar technology with architectural style and art, to help urban beautification and investigate the increase in solar panels' efficiency ...
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The solar tree is a combination of technology and art that is considered as the application of solar energy in the art of urban architecture. This study aims to combine solar technology with architectural style and art, to help urban beautification and investigate the increase in solar panels' efficiency by focusing on the optimal slope and no shading in the form of a new solar tree structure. In this paper, the best angle for placing panels on tree branches to increase Shiraz's maximum efficiency has been calculated. The best angle is done with the help of the NRI mathematical model. Also, the Fibonacci sequence, which originates from nature and real trees, has been used to minimize shadows on this tree. The panels' optimal slope calculations are performed using MATLAB software. Also, the monthly efficiency changes resulting from the optimal slope have been calculated and displayed. By analyzing the computational relationships and their implementation by PVsyst simulator, the optimal annual slope of solar panels obtained 30 degrees. By implementing it in the solar tree structure, the proposed annual efficiency of the model has increased by 12% compared to the fixed state. This article examines the technical methods of using solar systems in urban architecture with emphasis on integration methods. In the proposed and implemented solar tree model with the ability to adjust the optimal angle and beautify passages, parks and recreation centers, it is possible to charge electronic equipment such as mobile phones, tablets, and electric bicycles through clean solar energy.
Computational Fluid Dynamics (CFD)
Milad Darabi Boroujeni; Ehsan Kianpour
Abstract
In this study, cooling of a hot obstacle in a rectangular cavity filled with water-CuO nanolfuid has been examined numerically. This cavity has an inlet and outlet and the cold nanofuid comes from the left side of the cavity and after cooling the hot obstacle, it goes out from the opposite site. All ...
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In this study, cooling of a hot obstacle in a rectangular cavity filled with water-CuO nanolfuid has been examined numerically. This cavity has an inlet and outlet and the cold nanofuid comes from the left side of the cavity and after cooling the hot obstacle, it goes out from the opposite site. All of the walls are insulated, and the SIMPLER algorithm has been employed for solving the governing equations. The effects of fluid inertia, magnetic field strength, volume fraction of nanoparticles, and the place of outlet on heat transfer rate has been scrutinized. According to the results, the average Nusselt number builds up as the outlet place goes down. In other words, when the outlet is located at the bottom of the cavity, the rate of the heat transfer is maximum. Moreover, by increasing the Reynolds number and volume fraction of nanoparticles, the average Nusselt number builds up as well.
Manufacturing Processes
Faiz F. Mustafa; Sadoon R. Daham
Abstract
Surface layer in many engineering applications is strengthened by ceramic grains where the main parts have higher structure toughness than the original material. This paper presents the effect of four process parameters that have been taken into consideration using Taguchi technique based on L9 orthogonal ...
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Surface layer in many engineering applications is strengthened by ceramic grains where the main parts have higher structure toughness than the original material. This paper presents the effect of four process parameters that have been taken into consideration using Taguchi technique based on L9 orthogonal array. These parameters are;1) transverse speed, 2) type of nano- powders, 3) rotational speed, and 4) groove’s depth friction stir welding T-joints aluminum alloy 6061-T6. This work combines welding T-joint sections and creating MMNCs in welding region simultaneously. The predicted optimum parameters and their percentage of contribution are estimated, utilizing the analysis of variance and signal to noise ratio techniques, depending on tensile test in skin and stringers direction, and hardness test of the joint. Optical microscope and scanning electron microscope (SEM) analysis are used to verify the microstructure and dispersion of nano-powders in welding joint. The best ultimate tensile stress (UTSskin) equal to (177MPa) for the skin welded part was obtained at the optimal conditions of 1550rpm rotational speed, 15mm/min transverse speed, Al2O3 type of powder and 1mm groove’s depth. SEM micrographic for metal matrix nanocomposite of all nine experiments revealed that the nano-particles are irregularly dispersed in nugget zone due to one pass. The rotational speeds of 960rpm, the transverse speed of 15mm/min, type of powder TiO2, and groove’s depth of 1.5mm, give the greatest hardness value of 80HV in nugget zone. The analysis of variance shows that the groove’s depth is the most significant parameter in this investigation.
Computational Fluid Dynamics (CFD)
M. S. Sharifi; M. Mahdi; K. Maghsoudi
Abstract
The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an ...
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The shape of the air flow in the interior is heavily influenced by the air distribution system and the way air enters and exits. By numerically simulating flow by computational fluid dynamics, one can determine the flow pattern and temperature distribution and, with the help of the results, provide an optimal design of the air conditioning system. In this study, a chamber was first constructed and the temperature distribution inside it was measured. There was a fan installed at the back of the chamber for drainage. At the chamber entrance, three inlet for entering the flow were considered. The air from the middle inlet was heated by a heater. To prevent heat loss, the body of the enclosure was insulated. Several temperature sensors were installed at certain positions of the chamber for temperature measurement. Using Fluent software, the model of a full-sized chamber was created. Meshing is a hybrid and was used as a boundary layer Mesh. The inlet and outlet temperature of the chamber and the air output rates as boundary conditions were used in the simulation. Numerical analysis for K-ε and K-ω turbulence models was performed and different wall conditions were investigated. The numerical simulation results were in good agreement with the measurement results. Using the K-ε turbulence model with a scalable wall function had a better accuracy than other models. Changes in velocity and temperature were presented in graphs and contours at different positions of the compartment.
Computational Fluid Dynamics (CFD)
Aydin Zabihi; Nader Pourmahmoud
Abstract
Cooling tubes are inserted into the desiccant dehumidifier liquid of a 3-fluid liquid-to-air membrane energy exchanger (LAMEE) to regulate the temperature of the dehumidifier liquid. As a result, the 3-fluid LAMEE's performance is significantly influenced by the refrigerated tubes. The numerical ...
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Cooling tubes are inserted into the desiccant dehumidifier liquid of a 3-fluid liquid-to-air membrane energy exchanger (LAMEE) to regulate the temperature of the dehumidifier liquid. As a result, the 3-fluid LAMEE's performance is significantly influenced by the refrigerated tubes. The numerical analysis of the present work shows that the number of chilled tubes and their inner diameter affect the effectiveness (total, latent, and sensible) rate of moisture removal, adequate cooling power, and exergy loss. Additionally, the dehumidifier liquid channel receives the addition of wavy cooling tubes for the first time. The relationship between wave height and wave length is known as wave steepness and its impact on efficiency and energy loss is also examined. Numerical studies show that the number and inner diameter of the cooling tubes have a direct correlation with the efficiency of the 3-fluid LAMEE. The improved the efficiency, the more cooled tubes there are and the larger their diameter. Furthermore, both exergy loss and without dimensions exergy loss increase with the quantity and diameter of refrigerated tubes. The sensible and latent effectiveness of the 3-fluid LAMEE is increased by the wavy refrigeration tubes as compared to straight tubes; the augmentation of the sensible and latent effectiveness increases with wave steepness.
Fluid Mechanics
S. M. Hosseinalipour; P. R. Masharei; M. J. Moslemani
Abstract
Laminar mixing of glycerin in a chaotic mixer is carried by means of the blob deformation method. The mixer was a cylindrical vessel with two rotational blades which move along two different circular paths with a stepwise motion protocol. The flow visualization was performed by marking of the free surface ...
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Laminar mixing of glycerin in a chaotic mixer is carried by means of the blob deformation method. The mixer was a cylindrical vessel with two rotational blades which move along two different circular paths with a stepwise motion protocol. The flow visualization was performed by marking of the free surface of the flow with a tracer. The effects of controlling parameters such as rotational speed of blades, blades length, and rotational speed amplitude on mixing efficiency and time were analyzed by measuring of the area covered by the tracer. The results revealed that increasing rotational speed intensifies stretching and folding phenomenon, and consequently better mixing can be obtained. Also, the better condition in flow kinematic was provided to blend as stepwise motion protocol with wider amplitude adopted. A reduction in mixing time could be observed as the blades with longer length were used. In addition, it was also found that the promotion of mixing by rotational speed is more effective than that of two other parameters. The quantitative data and qualitative observations proved the potential of proposed chaotic mixer in wide range of industrial processes including chemical reaction and food processing in which laminar mixing is required.
Meshless Numerical Methods
R. Shamsoddini; B. Abolpour
Abstract
One of the main problems in liquid transfer tanks is the sloshing phenomenon. This phenomenon, which is associated with regular or irregular liquid waves inside the tank, can cause many risks. One of the most widely applied methods to control the fluctuations caused by the sloshing phenomenon is the ...
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One of the main problems in liquid transfer tanks is the sloshing phenomenon. This phenomenon, which is associated with regular or irregular liquid waves inside the tank, can cause many risks. One of the most widely applied methods to control the fluctuations caused by the sloshing phenomenon is the use of baffles. Baffles are usually installed vertically or horizontally on the inner wall of the tank. In uniform samples (simple baffle), the hydrodynamic force on the baffle is significant. Therefore, in this research, mesh baffle from the category of permeable baffles is introduced and tested, which can significantly reduce the hydrodynamic forces on the baffle. Therefore, in the present work, the sloshing phenomenon in a rectangular tank is first modeled by smoothed particle hydrodynamics and validated. Then, the tank with a simple baffle and mesh baffle are modeled and examined. During the numerical solution (in each time interval), the hydrodynamic forces acting on the baffles are monitored and extracted. The comparison of the obtained results shows that in addition to reducing the fluctuations of the sloshing phenomenon, the mesh baffle also creates a lower hydrodynamic resistance force.
Manufacturing Processes
S. Khalilpourazary; J. ahmadi
Abstract
Reaming is a common finishing process for improving the drilled holes surface quality. Choosing an appropriate finishing method in drilling process has a significant effect on the surface quality of holes and in decreasing the process total cost and time. In this study, four similar holes were drilled ...
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Reaming is a common finishing process for improving the drilled holes surface quality. Choosing an appropriate finishing method in drilling process has a significant effect on the surface quality of holes and in decreasing the process total cost and time. In this study, four similar holes were drilled on the AISI 4340 workpiece with different two pair feed rates. The drilling process was performed with a conventional cutting fluid, an emulsion of water and ECOCOOL 3015 GS-W. The surface roughness values after drilling process were measured using a portable roughness tester. Then, two distinct sizes of alumina micro-particles were used in the cutting fluid discretely to perform finishing process of the holes with a specific cylindrical tool. A comparison of the surface roughness measurements after the finishing process showed a significant decrease in the arithmetic surface roughness and ten-point mean roughness values of the drilled holes. The values were very close to the surface roughness limits in reaming process of the holes.
Computational Fluid Dynamics (CFD)
G. Shajari; M. Abbasi; M. Khaki Jamei
Abstract
In this study, comprehensive numerical simulations were conducted to examine laminar pulsatile developing flows through flat channels. The developing velocity fields and the hydrodynamic entry length were explored for the Reynolds numbers from 20 to 200, and the low and intermediate non-dimensional pulsation ...
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In this study, comprehensive numerical simulations were conducted to examine laminar pulsatile developing flows through flat channels. The developing velocity fields and the hydrodynamic entry length were explored for the Reynolds numbers from 20 to 200, and the low and intermediate non-dimensional pulsation frequency or the Womersley number (1.08 ≤Wo≤ 8.86). For all simulations, the pulsating amplification factor was considered from zero to one, (0 ≤A≤ 1), and to achieve more practical and relevant outcomes, time-dependent parabolic inlet velocity profiles were applied. The outcomes reveal that for the higher values of the pulsation frequency or the Womersley number (6 ≤ Wo ≤ 8.66), the maximum pulsatile entranced length during a cycle is close to the inlet length of the mean component of the flow. On the other hand, for the rest of the Womersley number range (1.08 ≤ Wo < 6), and high amplification factor (0.5 ≤ A), the value of the entrance length increases and is significantly different from the development length of the steady component. Moreover, the results demonstrate that the entry length correlates with the Womersley number through a power-law function, whilst it has linear correlations with the Reynolds number and the amplification factor. Further, using the result of the accomplished numerical study, a practical correlation of the entrance length is offered to be used in the design phase for any type of pulsatile flow through the flat channels.
Biomechanics
Ali Asghar Taheri; Faramarz Talati
Abstract
Hyperthermia is one of the first applications of nanotechnology in medicine by using micro/nano magnetic particles that act based on the heat of ferric oxide nanoparticles or quantum dots in an external alternating magnetic field. In this study, a two-dimensional model of body and tumor tissues embedded ...
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Hyperthermia is one of the first applications of nanotechnology in medicine by using micro/nano magnetic particles that act based on the heat of ferric oxide nanoparticles or quantum dots in an external alternating magnetic field. In this study, a two-dimensional model of body and tumor tissues embedded is considered. Initially, the temperature distribution is obtained with respect to tumor properties and without the presence of an electromagnetic field. Then, the effect of the electromagnetic field on the temperature distribution is studied. The results are compared with those of other papers. The results indicate that the use of the electromagnetic field causes a significant rise in the tumor temperature; however, the risk of damage to the healthy tissues surrounding the cancerous tissue seems to be high. Then, the micro/nanoparticles are injected into the tumor tissue to focus energy on cancerous tissue and maximally transfer the heat onto the tissue. The temperature distribution in the state is compared with the case with no nanoparticles and other numerical works. The results demonstrate that with the injection of nanoparticles into the tumor, the maximum temperature location is transferred to the center of the tumor and also increases to 6°C. After determining the temperature distribution in the presence of nanoparticles, the effects of different variables of the problem are studied. According to the obtained results, the increase in the concentration and radius of nanoparticles have a positive effect on the temperature distribution in the tissue; on the other hand, the increase in the frequency and size of the electrodes have a negative effect. The relevant equations are solved numerically using the finite difference method.
Smart Material
Majid Jabbari
Abstract
Electrical energy can be harvested from the vibrations of piezoelectric plates. The behavior of the piezoelectric plate is simulated using electromechanical coupling. Given the large strain experienced by the flexible plate, the linear theory is inadequate; therefore, the effect of Von Karman strain ...
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Electrical energy can be harvested from the vibrations of piezoelectric plates. The behavior of the piezoelectric plate is simulated using electromechanical coupling. Given the large strain experienced by the flexible plate, the linear theory is inadequate; therefore, the effect of Von Karman strain must be considered. This paper investigates and validates the vibrational behavior of a piezoelectric nonlinear plate. Specifically, it employs coupled equations for a multilayered plate, incorporates Von Karman’s nonlinear strain, and applies Mindlin’s first-order shear deformation theory. The electrical response is obtained through finite element analysis of the piezoelectric nonlinear plate in Matlab. Different boundary conditions are considered to verify the results, including clamped edges, simply supported edges, and a combination of two simply supported and two clamped edges. The electrical response of the open-circuit case under harmonic excitation is presented. Furthermore, the phenomenon of voltage cancellation during plate vibrations is studied, and a method for enhancing energy harvesting performance using separated electrodes is proposed. The results indicate that, across all cases, the voltage response with a continuous electrode is lower than with segmented electrodes at the first natural frequency.
Power Generation
R. Nasrin; M. Saddam Hossain
Abstract
Photovoltaic (PV) module is one of the most useful, sustainable and non-harmful products in the field of renewable energy. It offers longer service period for least maintenance cost. The elements of PV are abrasive, easy for designing, and their structure like the stand-alone technique gives production ...
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Photovoltaic (PV) module is one of the most useful, sustainable and non-harmful products in the field of renewable energy. It offers longer service period for least maintenance cost. The elements of PV are abrasive, easy for designing, and their structure like the stand-alone technique gives production from micro to mega-power level. A 3D numerical system of PV module has been built up and solved applying FEM technique-based software COMSOL Multiphysics in this article. The average solar irradiation and optimum tilt angle for six divisions (Dhaka, Chittagong, Rajshahi, Khulna, Barishal and Sylhet) in Bangladesh have been calculated. The effects of solar radiation, angle of inclination, ambient temperature, and partial shading on temperature of solar cell, electrical power and PV module's electrical efficiency have been investigated. It has been observed from the results that the greatest value of electrical power 15.14 W is found in Rajshahi for solar radiation 209 W/m2. The highest electrical efficiency is found as 12.85% in Sylhet at irradiation level of 189 W/m2. For every 1° increase of inclination angle, electrical power and electrical efficiency level devalue by 0.06 W and 0.05%, respectively. Results also show that the efficiency level decreases from 14.66 to 11.32% due to partial shading area from 0 to 40%. PV module's electrical power; and electrical efficiency reduces approximately 0.01 W and 0.01%, respectively due to every 1°C addition of solar cell temperature.
Composite Materials
Nabard Habibi; Y. Ahmadi
Abstract
Water storage tanks are amongst the essential infrastructures, and the study of their natural frequencies plays a pivotal role in predicting and detecting dynamic behavior. Therefore, it helps to the uninterrupted operation of an industrial plant and the use of tank water in emergencies. This paper studies ...
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Water storage tanks are amongst the essential infrastructures, and the study of their natural frequencies plays a pivotal role in predicting and detecting dynamic behavior. Therefore, it helps to the uninterrupted operation of an industrial plant and the use of tank water in emergencies. This paper studies the influence of different shell materials, including steel, aluminum, and laminated composites with three types of different fiber orientations, on the natural frequencies of thin-walled aboveground water storage tanks that have pinned boundary conditions at the base. Models investigated in this paper, either the roof is without an internal support structure or else a group of columns and radial beams are used for supporting it. These huge tanks had the height to diameter ratio of 0.4, and a water surface at 90% of the height of the tank's cylinder. The thicknesses of the cylindrical shells are tapered. The tanks without internal support included the vibrations that affect the cylinder mode shapes or the roof mode shapes or simultaneously both the cylinder and roof mode shapes. On the other hand, the mode shapes of the tanks with internal support affect predominantly only the cylinder. Among the studied tanks, the third type of composite tanks had the highest rigidity, and the first type of composite tanks had the lowest rigidity. The natural frequencies related to the first modes of vibrations for cylinder and roof shells with a wide range of circumferential wave numbers (n) and an axial half-wave (m) are studied.
Mohammad Reza Shabgard; Reza Rostami Heshmatabad
Abstract
In this study, relationship between effect of machining parameters on machining characteristics and surface morphology was studied in electrochemical machining (ECM). The characteristics were Material Removal Rates (MRR), Over Cut (OC), Surface Roughness (SR) and surface morphology. The results show ...
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In this study, relationship between effect of machining parameters on machining characteristics and surface morphology was studied in electrochemical machining (ECM). The characteristics were Material Removal Rates (MRR), Over Cut (OC), Surface Roughness (SR) and surface morphology. The results show that MRR is increased by increasing current but OC is decreased. Increasing concentration causes to increase MRR, OC and SR. Also, the analysis of surface morphology shows that the electrolyte type affects the dissolution mechanism and surface layer formation in ECM. There are cavities in NaCl and KCl that their diameter, depth and distribution on the machined surface are changed by parameters and their diameters were 4μm to 9μm. Increasing ion concentration causes to enhance the diameter size and depth of created cavities on work piece but their uniform distribution decreases, while the current has a reverse effect on them. On the other hand, an oxide layer is formed on the machined surface in NaNO3 and by increasing current and concentration, breaking and the anion cavity effect are increased on this layer. So, increasing the MRR and SR is due to this phenomenon in NaNO3.
Robotics
k. Alipour; m. Ghiasvand; B. Tarvirdizadeh
Abstract
In this paper, the important formation control problem of nonholonomic wheeled mobile robots is investigated via a leader-follower strategy. To this end, the dynamics model of the considered wheeled mobile robot is derived using Lagrange equations of motion. Then, using ADAMS multi-body simulation software, ...
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In this paper, the important formation control problem of nonholonomic wheeled mobile robots is investigated via a leader-follower strategy. To this end, the dynamics model of the considered wheeled mobile robot is derived using Lagrange equations of motion. Then, using ADAMS multi-body simulation software, the obtained dynamics of the wheeled system in MATLAB software is verified. After that, in order to generate and keep the desired formation, a Fuzzy Logic Controller is designed. In this regard, the leader mobile robot is controlled to follow a reference path and the follower robots use the Fuzzy Logic Controller to keep constant relative distance and constant angle with respect to the leader. The efficiency of the suggested dynamics-based formation controller has been proved using several computer simulations under different situations and desired trajectories. Also, the performance of the follower robot in path tracking is checked in the presence of receiving noisy data from the leader robot.
Composite Materials
A. A. Azemati; H. Khorasanizadeh; B. Shirkavand Hadavand; G. A. Sheikhzadeh
Abstract
One of the ways to waste energy in buildings is wasting it from the walls. For this reason, insulating materials are used to prevent the loss of energy in buildings. Typically, common insulations are high thickness and thin coatings are used less. The purpose of this research is to introduce nanocomposite ...
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One of the ways to waste energy in buildings is wasting it from the walls. For this reason, insulating materials are used to prevent the loss of energy in buildings. Typically, common insulations are high thickness and thin coatings are used less. The purpose of this research is to introduce nanocomposite thin polymer coatings and its effect on thermal conductivity. For achieving this, chemically modified nano zirconium oxide and nano aluminum oxide in three different weight percentages (1, 3, and 5%) were used in polyurethane matrix for preparing nanocomposite coatings. To study thermal conductivity, the metallic plates are coated with prepared nanocomposites and the thermal conductivity of the samples was measured. The results show that by adding zirconium oxide and aluminum oxide nanoparticles in polyurethane matrix, the thermal conductivity of coatings in all three weight percentages compared to the coating without nanoparticles, decreased. The lowest thermal conductivity was found for 5% nano aluminum oxide composition, which, compared to the conductivity of the pure polyurethane resin, has decreased about 40% that leading to a decrease in the surface heat flux.
Composite Materials
Hamed Khosravi; Reza Eslami-Farsani
Abstract
In the present study, multiscale nanosilica/E-glass/epoxy anisogrid composite panels were investigated for flexural properties as a function of nanosilica loading in the matrix (0, 1, 3 and 5 wt. %). The surface of the silica nanoparticles was firstly modified with 3-glycidoxypropyltrimethoxysilane. ...
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In the present study, multiscale nanosilica/E-glass/epoxy anisogrid composite panels were investigated for flexural properties as a function of nanosilica loading in the matrix (0, 1, 3 and 5 wt. %). The surface of the silica nanoparticles was firstly modified with 3-glycidoxypropyltrimethoxysilane. The Fourier transform infrared spectroscopy revealed that the organic functional groups of the silane were successfully chemically grafted on the surface of the nanoparticles. It was illustrated that flexural properties of the composite panel loaded from the skin side can be significantly enhanced by incorporating silica nanoparticles. From the 3-point flexural test, it was found that using of 3 wt. % nanosilica was the most effective in increasing the load bearing capacity and energy absorption value, while the specimen containing 5 wt. % nanosilica demonstrated the highest flexural stiffness. The results obtained for the anisogrid panels loaded from the skin side showed that these structures displayed excellent damage resistance which is represented by their energy absorption capability. Moreover, a significant portion of energy absorbed after the primary failure at the peak load. Finally, the results correlated well with the observation of field emission scanning electron microscopy micrographs where the nanocomposite panels exhibited higher degree of fiber-matrix interfacial strength and also enhanced matrix characteristics, imparted by the incorporation of surface modified silica nanoparticles.
Nonlinear Solution
Y. M. Kong; W. Y. Tey
Abstract
The theory of superposition of waves has been widely deployed in many engineering applications such as medical imaging, engineering measurements, and wave propagation in structures. However, these applications are prone to the interference of unwanted waves. The root cause of the weakness could be ascribable ...
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The theory of superposition of waves has been widely deployed in many engineering applications such as medical imaging, engineering measurements, and wave propagation in structures. However, these applications are prone to the interference of unwanted waves. The root cause of the weakness could be ascribable to the wave propagation pattern, which is not actively controlled. A new concept of imposing a time-lagging effect on the source of the wave as an active wave emission strategy is introduced and discussed in this paper. A numerical solver has been developed based on the finite volume Euler explicit method to investigate the wave propagation pattern when there is a time-lagged effect and frequency difference at the source of the wave. Our results reveal that time-lagged wave propagation will be more immune to the disturbance of other waves. The larger the time lag, the more resilient the wave is to resist the interference of other waves, even at a higher frequency. Time-lagged waves can be regarded as a promising active wave emission method that has many potential and robust engineering applications to be explored in the future.
Heat and Mass Transfer
J. Zareei; S. H. Hoseyni; M. Elveny
Abstract
In this paper, the effect of boundary layer excitation on increasing the heat transfer coefficient of water/carbon nanotube (CNT) nanofluid and water/aluminum oxide (Al2O3) nanoparticles has been investigated. The turbulent flow equations inside the pipe with RNG K-ε turbulence model are solved ...
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In this paper, the effect of boundary layer excitation on increasing the heat transfer coefficient of water/carbon nanotube (CNT) nanofluid and water/aluminum oxide (Al2O3) nanoparticles has been investigated. The turbulent flow equations inside the pipe with RNG K-ε turbulence model are solved employing fluent software. The results show that the use of water/CNT nanofluid significantly increases the heat transfer coefficient of the convection. There is no such increase for water-aluminum oxide nanoparticles. If the volumetric percentage of the carbon nanotube increases, the rate of increase in the heat transfer coefficient and the flow pressure drop will increase. Therefore, the use of water/CNT nanofluid with lower volumetric percentages is better for improving the convective heat transfer. Also, by placing the barrier on the inner wall of the tube and stimulating the boundary layer, the heat transfer coefficient thereafter increases in the excitement area. In the present study, the use of three obstacles behind each other has increased the average heat transfer coefficient by 16.7%.
Control
Mohamed A. Shamseldin; Mohamed Sallam; A. M. Bassiuny; A. M. Abdel Ghany
Abstract
This paper presents a practical implementation for a new formula of nonlinear PID (NPID) control. The purpose of the controller is to accurately trace a preselected position reference of one stage servomechanism system. The possibility of developing a transfer function model for experimental setup is ...
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This paper presents a practical implementation for a new formula of nonlinear PID (NPID) control. The purpose of the controller is to accurately trace a preselected position reference of one stage servomechanism system. The possibility of developing a transfer function model for experimental setup is elusive because of the lack of system data. So, the identified model has been developed via gathering experimental input/output data. The performance of the enhanced nonlinear PID (NPID) controller had been investigated by comparing it with linear PID controller. The harmony search (HS) tuning system had built to determine the optimum parameters for each control technique based on an effective objective function. The experimental outcomes and the simulation results show that the proposed NPID controller has minimum rise time and settling time through constant position reference test. Also, the NPID control is faster than the linear PID control by 40% in case of variable position reference test.
Internal Combustion Engine
Upendra Rajak; Prerana Nashine; Tikendra Nath Verma
Abstract
The unvarying condition diesel engines used for commercial applications, transportation and industries lead to the crisis of petroleum fuel diminution and ecological squalor caused due to exhaust gases. Therefore, in this paper optimization of the use of MSB in naturally aspirated, direct injection diesel ...
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The unvarying condition diesel engines used for commercial applications, transportation and industries lead to the crisis of petroleum fuel diminution and ecological squalor caused due to exhaust gases. Therefore, in this paper optimization of the use of MSB in naturally aspirated, direct injection diesel engines, parameters of pure diesel (D100), 80% diesel + 20% microalgae spirulina (B20), 60% diesel + 40% microalgae spirulina (B40) and pure microalgae spirulina biodiesel (B100) were investigated at various fuel injection pressures (FIP) of 18 to 26 MPa and stationary injection timings (23.5° b TDC). The result shows that optimum effect can be obtained in 22 MPa FIP, with B20 bio-diesel without compromising the performance against diesel. B20 blend presented less NOX and smoke emissions by 13.7% and 22.2% respectively with no significant change in engine performance when compared to diesel at full load operating condition. The simulation and experiment results are verified at the same operating conditions.
