Fluid Mechanics
Payam Rahim Masharei; Seyed Mostafa Hosseinalipour; Mohammad Javad 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
Saman Khalilpourazary; jamal 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.
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.
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
Ali Akbar Azemati; Hossain Khorasanizadeh; Behzad Shirkavand Hadavand; Ghanbar Ali 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
Reza Eslami-Farsani; Hamed Khosravi
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 (3-GPTS). ...
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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 (3-GPTS). The fourier transform infrared (FTIR) spectroscopy revealed that the organic functional groups of the silane were successfully 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. The use 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. From the results obtained for the anisogrid panels loaded from the skin side, it was found 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 (FESEM) 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.
Fluid Mechanics
Neetu Kanaujia; Uday Singh Rajput
Abstract
Unsteady flow with magneto-hydrodynamics and heat generation through porous medium past an impulsively started vertical plate with constant wall temperature and mass diffusion is considered here. The effect studied is a combination of Hall current and chemical reaction. The motivation behind this study ...
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Unsteady flow with magneto-hydrodynamics and heat generation through porous medium past an impulsively started vertical plate with constant wall temperature and mass diffusion is considered here. The effect studied is a combination of Hall current and chemical reaction. The motivation behind this study is the applications of such kind of problems in industry. In many industrial applications electrically conducting fluid is subjected to magnetic field. The fluid is passed through porous medium. The flow may be on a plate. There may be substance on the plate which may cause chemical reaction. The solution of flow model studied here is obtained by using Laplace transform method. The respective profiles have been drawn for velocity. The numerical data have been obtained using latest software techniques available. The profiles have been analyzed and discussed. The values of Nusselt number, Sherwood number, and drag on plate have been tabulated for analysis. The findings have been summarized in conclusion section.
Mechanics of Materials
Aji Abdillah Kharisma; Haris Rudianto; Achmad Benny Mutiara; Sulistyo Puspitodjati
Abstract
Titanium alloys have been extensively explored and fabricated for application in several engineering fields. Its superior mechanical properties, Ti-10Mo-xCu alloy has potential applications in hip implants. Determining mechanical qualities via experimental methods takes a long time, especially when carried ...
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Titanium alloys have been extensively explored and fabricated for application in several engineering fields. Its superior mechanical properties, Ti-10Mo-xCu alloy has potential applications in hip implants. Determining mechanical qualities via experimental methods takes a long time, especially when carried out in compression and tensile testing. Therefore, material design modeling using an MD simulation method approach is used to evaluate the mechanical properties of the compression and tensile tests of the Ti-10Mo-xCu alloy. In this research, material design through computer modeling is carried out at 300 K in the x <100> direction of the Ti-10Mo alloy with the addition of Cu composition at 3, 6, and 9 wt.% to evaluate the properties of the alloy. The simulation results of the Cu addition produces maximum stresses of 603, 160, and 236 Mpa, respectively. The experimental method in the compression test shows a decrease in the maximum stress after adding Cu to the Ti-10Mo alloy. It has the same trend value as the compression test outcomes on the experiment and MD simulation method. The result of tensile strength for the Ti-10Mo-xCu alloy are 7056.8, 7238.2, and 7433.1 Mpa, respectively. MD simulation of the results of crack propagation in tensile strength is successfully performed based on the increase at high strain until plasticity occurs in the alloy.
Heat and Mass Transfer
Majid Kerdarian; Ehsan Kianpour
Abstract
In this study, the finite volume method and the SIMPLER algorithm is employed to investigate forced convection and entropy generation of Cu-water nanofluid in a parallel plate microchannel. There are four obstacles through the microchannel, and the slip velocity and temperature jump boundary conditions ...
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In this study, the finite volume method and the SIMPLER algorithm is employed to investigate forced convection and entropy generation of Cu-water nanofluid in a parallel plate microchannel. There are four obstacles through the microchannel, and the slip velocity and temperature jump boundary conditions are considered in the governing equations to increase the accuracy of modeling. The study is conducted for the Reynolds numbers in the range of 0.1<Re<10, Knudsen numbers ranging of 0<Kn<0.1, and volume fraction of nanoparticles ranging of 0<φ
Heat and Mass Transfer
Sandeep Naramgari; Raju C.S.K; Jagadeesh Kumar M.S
Abstract
In this study, we presented a mathematical model for analyzing the heat source/sink effect on magnetohydrodynamic two-dimensional ferrofluid flow past a cone and a vertical plate in the presence of volume fraction of ferrous nanoparticles. The governing partial differential equations are transformed ...
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In this study, we presented a mathematical model for analyzing the heat source/sink effect on magnetohydrodynamic two-dimensional ferrofluid flow past a cone and a vertical plate in the presence of volume fraction of ferrous nanoparticles. The governing partial differential equations are transformed as ordinary differential equations making use of similarity solutions and solved numerically with the aid of Runge-Kutta based shooting technique. The limiting case of the present results shows a good agreement with the published results. We presented solutions for the flow over a cone and a vertical plate cases. The influence of dimensionless parameters on velocity and temperature profiles along with the friction factor coefficient and the heat transfer rate are analyzed with the help of graphs and tables. It is found that the rising value of the volume fraction of ferrous nanoparticles enhances the friction factor coefficient and heat transfer rate. It is also found that heat transfer performance of the flow over a plate is comparatively higher than the flow over a cone.
Dynamic Response
Y. H. Park
Abstract
A hydraulically driven mold oscillator challenges estimating the dynamic state variables precisely. Significantly, the additional stiffness effect of hydraulic oil is variable according to operating conditions, and it is hard to formulate it as a mathematical expression. This study investigates the dynamic ...
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A hydraulically driven mold oscillator challenges estimating the dynamic state variables precisely. Significantly, the additional stiffness effect of hydraulic oil is variable according to operating conditions, and it is hard to formulate it as a mathematical expression. This study investigates the dynamic characteristics of a mold oscillator operated by two hydraulic cylinders with other springs and dampers to determine the non-linear effect and estimate exact dynamic state variables to improve the accuracy control. The mold oscillator is excited in either step oscillation or sine-sweeping oscillation to measure its dynamic behaviors, including mold displacement and hydraulic cylinder pressure. Due to non-linear properties, the dynamic behavior change according to excitation conditions during sine-sweeping oscillation. Primarily, peak frequencies around 50 Hz are found from experimental pressure-displacement data in the frequency domain. To identify the oscillating mechanisms, equivalent 1-DOF and 2-DOF mass-damper-spring models for the mold oscillator are established. The fundamental system property is derived by experiment and a finite element multi-body dynamics model. In addition, inverse dynamics and numerical analysis are applied to derive the unknown force from the hydraulic servo system and structural characteristics. The unknown force is related to a friction problem and an elastic deflection by relative components near the mold. For high accuracy control, the unknown force model by an additional mass-spring model that causes high-frequency vibrations at 49, 48, 47, 46, or 45 Hz is suggested to formulate the equation of motion with the additional vibrations without any arbitrary modeling process.
Energy Science and Technology
H. Khoshkam; K. Atashkari; M. Borji
Abstract
Carbon deposition has a serious effect on the failure mechanism of solid oxide fuel cells. A comprehensive investigation based on a two-dimensional model of a solid oxide fuel cell with the detailed electrochemical model is presented to study the mechanism and effects of carbon deposition and unsteady ...
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Carbon deposition has a serious effect on the failure mechanism of solid oxide fuel cells. A comprehensive investigation based on a two-dimensional model of a solid oxide fuel cell with the detailed electrochemical model is presented to study the mechanism and effects of carbon deposition and unsteady state porosity variation. Studies of this kind can be an aid to identify the SOFC optimal working conditions and provide an approximate fuel cell lifetime. It has been revealed that, due to carbon deposition, the porosity coefficient of the fuel cell decreases. Consequently, a reduction in the amount of fuel consumption along the fuel cell and the chemical and electrochemical reaction rates are resulted which can be clearly seen in the off-gases molar ratio. The percentage of output fuel changes in the timeframe is useful information for optimizing CHP systems including fuel cells. The percentage of the output water vapor, which usually increases compared to the input, decreases by 17% at the end of the working period. Also, unreacted methane in the output of the fuel cell increased by 12%; in other words, it is wasted. The other consequence of carbon deposition reduced electrochemical and chemical reaction rates and the reduction of temperature difference along the cell. The study shows that after 145 working days, the temperature difference along the cell varies from 117 °C for the starting time to 7 °C. Also, by reducing the current density, the cell output power density decreases by 72% after 145 working days.
Fluid Mechanics
Ganesh Kumar; Ramesh G K; Sabir Ali Shehzad; Gireesha B.J
Abstract
In this article, we examined the behavior of chemical reaction effect on a magnetohydrodynamic Prandtl nanofluid flow due to stretchable sheet. Non-linear thermally radiative term is accounted in energy equation. Constructive transformation is adopted to formulate the ordinary coupled differential equations ...
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In this article, we examined the behavior of chemical reaction effect on a magnetohydrodynamic Prandtl nanofluid flow due to stretchable sheet. Non-linear thermally radiative term is accounted in energy equation. Constructive transformation is adopted to formulate the ordinary coupled differential equations system. This system of equations is treated numerically through Runge Kutta Fehlberg-45 method based shooing method. The role of physical constraints on liquid velocity, temperature and concentration are discussed through numerical data and plots. Also, the skin friction co-efficient, local Nusselt number and local Sherwood numbers are calculated to study the flow behavior at the wall, which is also presented in tabular form. A comparative analysis is presented with the previous published data in special case for the justification of the present results. The output reveals that for larger values of elastic and Prandtl parameter, the thickness of momentum layer enhanced and the rates of both heat and mass transport reduced. Also, increment of slip parameter decelerated both temperature and concentration filed while nonlinear form thermal radiation rapidly increases the temperature.
Manufacturing Processes
A. Ravendran; S. Rianmora
Abstract
Edge is an indispensable characteristic of an image, defined as the contour between two regions with significant variance in terms of surface reflectance, illumination, intensity, color, and texture. Detection of edges is a basic requirement for diverse contexts for design automation. This study presents ...
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Edge is an indispensable characteristic of an image, defined as the contour between two regions with significant variance in terms of surface reflectance, illumination, intensity, color, and texture. Detection of edges is a basic requirement for diverse contexts for design automation. This study presents a guideline to assign appropriate threshold and sigma values for the Canny edge detector to increase the efficiency of additive manufacturing. The algorithm uses different combinations of threshold and sigma on a color palette, and the results are statistically formulated using multiple regression analysis with an accuracy of 95.93%. An image-based acquisition technique system is designed and developed for test applications to create three-dimensional objects. In addition, a graphical user interface is developed to convert a selected design of a complex image to a three-dimensional object with the generation of Cartesian coordinates of the detected edges and extrusion. The developed system reduces the cost and time of developing an existing design of an object for additive manufacturing by 20% and 70%, respectively.
Computational Fluid Dynamics (CFD)
A. Moughbul Basha Shaik; B. Mithilesh Kumar Sahu
Abstract
The new and advance technologies for higher performance and lower maintenance are required to operate gas turbines at higher operating temperatures. Higher turbine inlet temperature results in higher blade metal temperatures. These variations in temperatures of the blade material must be limited ...
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The new and advance technologies for higher performance and lower maintenance are required to operate gas turbines at higher operating temperatures. Higher turbine inlet temperature results in higher blade metal temperatures. These variations in temperatures of the blade material must be limited such that the blades have a sufficient life span. To make blade material temperature within the limits, the coolant air is bled from the compressor to protect the outer surface of the turbine blade from the hot gases. The purpose of this study is to investigate the cooling performance of a blade with leading edge cooling holes. The numerical simulation approach using ANSYS Fluent has been considered. The analysis is performed by taking different hole geometries namely cylindrical (model 1) and tapered (model 2) on the leading edge of the turbine blade for different blowing ratios. The analysis also compares the cooling effectiveness of the blade for two different coolants namely air and nitrogen. The results show that for highest effectiveness hole (E3 hole), Model 1 and Model 2 comparison suggest that Model 1 has 1.2% more cooling effectiveness for air as coolant. For E3 hole, the comparison of Model 1 between two coolants show that film cooling effectiveness of the air gives 0.6% more film cooling effectiveness compared to nitrogen. The presented work helps researchers and blade manufacturers to select the correct hole geometry, coolant type, and determine the best blowing ratio to improve the film cooling efficiency of gas turbine blades with leading edge holes.
Vibration
M. Moradi; M. Bagheri Nouri
Abstract
In this paper, a new algorithm for studying elastic wave propagation in the phononic crystals is presented. At first, the displacement-based forms of elastic wave equations are derived and then the forms are discretized using finite difference method. So the new algorithm is called the displacement-based ...
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In this paper, a new algorithm for studying elastic wave propagation in the phononic crystals is presented. At first, the displacement-based forms of elastic wave equations are derived and then the forms are discretized using finite difference method. So the new algorithm is called the displacement-based finite difference time domain (DBFDTD). Three numerical examples are computed with this method and the results are compared with experimental measurements and the conventional FDTD method. Also, the computational cost of the new approach is compared with the conventional FDTD method. The comparison showed that the calculation time of the DBFDTD method is 37.5 percent less than that of the FDTD method.
Optimization
Omid Fathi; Hadi Kargarsharifabad
Abstract
Improving the efficiency of compressors has been one of the most important goals of researchers over the years. In this paper, three different methods are presented for parameterization and blade optimization of axial flow compressor. All methods consist of flow analysis tool, optimization algorithms, ...
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Improving the efficiency of compressors has been one of the most important goals of researchers over the years. In this paper, three different methods are presented for parameterization and blade optimization of axial flow compressor. All methods consist of flow analysis tool, optimization algorithms, and parametric geometry generation tool, that are different in each approach. Objective function is defined based on the aerodynamic performance of blade in the acceptable incidence angles range. A DCA blade is used as the initial guess for all methods. The performance of optimized blades and the initial blade are compared for evaluating the capability of various methods that a good agreement has been achieved. The results show that the value of performance improvement in each method depends on the number and type of the chosen parameters. All three methods have improved blade performance at the design incidence angle. However, only the first method shows significant performance improvement in off-design conditions.
