Research Paper
Heat and Mass Transfer
Javad Zareei; Seyyed Hissein Hoseyni; marischa 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 convection. There is no such increase for water-aluminum oxide nanoparticles. If the volumetric percentage of 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 and then 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%.
Research Paper
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, 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, 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 model's annual efficiency 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.
Research Paper
Heat and Mass Transfer
Ravi Kumar
Abstract
Theoretical investigation of Ohmic heating (Joule heating) and radiation on MHD Jeffery fluid model with porous material along the tapered channel with peristalsis is the focus of this study. Long wavelength and low-Reynolds number approximations are used in the mathematical modelling. Axial rate, pressure ...
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Theoretical investigation of Ohmic heating (Joule heating) and radiation on MHD Jeffery fluid model with porous material along the tapered channel with peristalsis is the focus of this study. Long wavelength and low-Reynolds number approximations are used in the mathematical modelling. Axial rate, pressure gradient, temperature, and heat transfer coefficient rate expressions are calculated. Plotting diagrams were used to analyse the impact of physical parameters on flow characteristics, which were then addressed in depth. It’s worth noting that raising the gravitational parameter, Jeffery fluid parameter, Hartmann number and Porosity parameter raises the fluid’s velocity. It's worth mentioning that as the Ohmic heating (Jeffery fluid) parameter and porosity parameter increases, the axial pressure gradient drops, and the temperature of the fluid rises. The rate of heatt transfer coefficient rises in region with an increase in the Radiation parameter, Heat generator parameter and Jeffery fluid parameter. Mathematica software is employed to seek out numerical results.
Research Paper
Robotics
Mohammad Mohammadi; Reza Dehghani; Ali Reza Ahmadi
Abstract
In this paper, a quadrotor with two manipulators constrained on a straight path is modeled and a robust adaptive controller is proposed for it. Adding two manipulators to quadrotor increases its capabilities and applications in industry. Here, these two manipulators are used to place the robot on a constraint ...
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In this paper, a quadrotor with two manipulators constrained on a straight path is modeled and a robust adaptive controller is proposed for it. Adding two manipulators to quadrotor increases its capabilities and applications in industry. Here, these two manipulators are used to place the robot on a constraint path so that the quadrotor can perform monitoring operations more accurately, because the under-actuated quadrotor becomes over-actuated by these constrained manipulators and one can use this feature to accurately control the position of the robot. Reduced form of motion equations are derived for the constrained quadrotor and based on this a robust adaptive controller is proposed. The nonlinear terms in the dynamic model are approximated by basic functions with constant weights and adaptive laws are designed by projection operator. Stability analysis is performed based on the Lyapunov theory. Evaluation of the presented controller is done by some numerical simulations. The simulation results showed that the robot tracks the reference path with bounded error in spite of dynamic uncertainties and wind force and satisfies the considered constraints.
Research Paper
Automation
Ali Mirmohammad Sadeghi; Abdollah Amirkhani; Behrooz Mashadi
Abstract
Recognizing a driver’s braking intensity plays a pivotal role in the development of modern driver assistance and energy management systems; and therefore, it is especially important to autonomous and electric vehicles. This paper aims at developing a system for recognizing a driver’s braking ...
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Recognizing a driver’s braking intensity plays a pivotal role in the development of modern driver assistance and energy management systems; and therefore, it is especially important to autonomous and electric vehicles. This paper aims at developing a system for recognizing a driver’s braking intensity based on the pressure produced in the brake master cylinder. In this regard, a model-based, synthetic data generation concept is used to generate the training dataset. This technique involves two closed-loop controlled models: an upper-level longitudinal vehicle dynamics model, and a lower-level brake hydraulic, dynamic model. The adaptive particularly tunable fuzzy particle swarm optimization algorithm is recruited to solve the optimal K-means clustering problem and to determine the best number of clusters and centroids into which the brake pressure data are to be divided. The obtained results reveal that the brake pressure data for a vehicle traveling the new European driving cycle can be best partitioned into two clusters. A driver’s braking intensity may, therefore, be clustered as moderate or intensive. With the ability to automatically recognize a driver’s pedal feel, the system developed in this research could be implemented in intelligent driver assistance systems as well as in electric vehicles equipped with intelligent, electromechanical brake boosters.
Research Paper
Hydraulic and Pneumatic Systems
Amir Saidani; Ali Fourar; Fawaz Massouh
Abstract
< p>The paper investigates temperature effect on water hammer in an isothermal pressurized copper pipe rig, for single and two phase flow. The study concerns pressure wave’s intensity, celerity and attenuation. Also, the cavities volume created during low pressure periods is inspected. The mathematical ...
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< p>The paper investigates temperature effect on water hammer in an isothermal pressurized copper pipe rig, for single and two phase flow. The study concerns pressure wave’s intensity, celerity and attenuation. Also, the cavities volume created during low pressure periods is inspected. The mathematical model of hyperbolic equations is described by the dynamic and continuity equations, which have been transformed by the characteristics method (MOC) into ordinary differential equations. Water hammer solver was built considering two different models of cavitation and column separation, the discrete vapor cavity model (DVCM) and the discrete gas cavity model (DGCM). In addition of the quasi-steady friction model, two unsteady friction models were incorporated into the code, the convolution based model proposed by Vardy & Brown and the instantaneous acceleration model proposed by Brunone. The simulations concern temperature range within 4°C to 95°C. Although the single and the two phase water hammer don’t behave with the same manner, the results obtained with the different models, show a significant influence of the temperature.
Research Paper
Heat and Mass Transfer
Sreenivasulu Pandikunta; Barinepalle Malleswari; POORNIMA T T; N Bhaskar Reddy
Abstract
This study emphasis on the upshots of non-linear radiation and electrical resistance heating on a three dimensional Jeffrey dissipating nanoflow in view of convective surface conditions. The initial set of nonlinear dimensional boundary layer equation are transformed into a system of ordinary differential ...
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This study emphasis on the upshots of non-linear radiation and electrical resistance heating on a three dimensional Jeffrey dissipating nanoflow in view of convective surface conditions. The initial set of nonlinear dimensional boundary layer equation are transformed into a system of ordinary differential equations with suitable similarity variables and then This study emphasis on the upshots of non-linear radiation and electrical resistance heating on a three dimensional Jeffrey dissipating nanoflow in view of convective surface conditions. The initial set of nonlinear dimensional boundary layer equation are transformed into a system of ordinary differential equations with suitable similarity variables and then solved by shooting method using Mathematica software. For various representative quantities, the behavior of the momentum, energy and species diffusion along with engineering quantities near the surface are figured for different estimations of the fluid properties. The examination of present outcomes has been made with the existing work which is good agreed. This study helps in understanding the heat transfer rate is predominant in the non-linear radiation compared to linear radiation. Jeffrey fluid model has the capacity of describing the stress relaxation property, which usually viscous fluid lags and this is exhibited clearly in the study. Shear stress descends as the fluid pertinent parameter ascends.
Research Paper
Computational Fluid Dynamics (CFD)
Mithilesh K Sahu; Moughbul Basha Shaik
Abstract
The new and advance technologies for higher performance and lower maintenance are required to operate the 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 the 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 the work is to investigate the cooling performance of 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. Result shows, for highest effectiveness hole (E3 hole), the Model 1 and Model 2 comparison suggest that Model 1 has 1.2% more cooling effectiveness for air as coolant. For E3 hole comparison of Model 1 between two coolants show that film cooling effectiveness of air gives 0.6% more film cooling effectiveness compared to nitrogen. The article concludes that 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.
Research Paper
Composite Materials
Aidin Ghaznavi; Mohammad Shariyat
Abstract
Studying the behavior of sandwich panels is very important due to their widespread use in different industries. Therefore, over the past decades, various theories have been proposed to study the behavior of these panels. In this paper a higher order global-local theory with 3D equilibrium-based corrections ...
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Studying the behavior of sandwich panels is very important due to their widespread use in different industries. Therefore, over the past decades, various theories have been proposed to study the behavior of these panels. In this paper a higher order global-local theory with 3D equilibrium-based corrections is presented to study behavior of thick and thin sandwich plate with flexible and auxetic core. In addition to correcting the results with 3D elasticity equations, another important advantage of the presented theory is the ability to consider the transverse core deformation of the sandwich panels. It should be mentioned that to study the behavior of thick sandwich panels, especially with soft core, the existence of this feature is very necessary and has a great effect on the accuracy of the obtained results. Comparison of the obtained results with those existing in valid references showed that the formulation of the provided finite element had a very good accuracy even for thick and thin sandwich plates. Finally, the effect of different material and geometrical parameters on the behavior of sandwich plates are carefully investigated using the presented theory.
Research Paper
Composite Materials
nabard habibi; yasaman 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 has ...
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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 has studied 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 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.
Research Paper
Fatigue
Liela Abbasiniyan; Seyed hamed Hoseini; Shirko faroughi
Abstract
In this paper, the crack propagation and branching in the pre-cracked and notched samples have been modeled using nonlocal peridynamic theory. The bond-based peridynamic model has been numerically implemented which make it possible to simulate the various features of dynamic brittle fracture such as ...
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In this paper, the crack propagation and branching in the pre-cracked and notched samples have been modeled using nonlocal peridynamic theory. The bond-based peridynamic model has been numerically implemented which make it possible to simulate the various features of dynamic brittle fracture such as crack propagation, asymmetries of crack paths and successive branching. The fracture simulation of thin plates made of a brittle material with different crack and notch patterns has been considered. The molecular dynamics open-source free LAMMPS code has been updated to implement the peridynamic theory based modeling tool for two-dimensional numerical analysis. The simulations show that, the simulations time significantly decreases which is the core and distracting deficiency of the peridynamic method. Moreover, the simulated results demonstrate the capability of peridynamic theory to precisely predict the crack propagation paths as well as crack branching during dynamic fracture process. The good agreement between simulation and experiments is achieved.
Research Paper
Stress Analysis
Sidda Reddy Bathini; Vijaya Vumar Reddy K
Abstract
This paper presents closed-form formulations of higher order shear deformation theory (HSDT) to analyse the functionally graded plates (FGPs) acted upon a thermo-mechanical load for simply supported (SS) conditions. This theory assumes nullity conditions for transverse stress on bottom and top face of ...
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This paper presents closed-form formulations of higher order shear deformation theory (HSDT) to analyse the functionally graded plates (FGPs) acted upon a thermo-mechanical load for simply supported (SS) conditions. This theory assumes nullity conditions for transverse stress on bottom and top face of the FGPs. Moreover, considers the influence of both stresses and strains in the axial and transversal direction. In these improvements an accurate parabolic variation is assumed in the thickness direction for transverse shear strains. Therefore, this theory omits the use of correction factor for accurately estimating the shear stress. The physical properties of the FGPs are considered to change along the thickness using a power law. The equilibrium relations and constriants on all edges are attained by considering the virtual work. Numerical evaluations are attained based on Navier’s approach. The exactness and consistency of the developed theory are ascertained with numerical results for deflections and stresses of SS FGPs and it is deemed that numerical solutions for thermo-mechanical load will utilize as a reference in the future.
Research Paper
Optimization
ehsanolah Assareh; Iman poultangari; Afshin ghanbarzadeh
Abstract
A common method utilized in wind turbines is pitch angle control whereby via varying the angle of wind turbine blades around their own axis, power generated at high speeds of wind is held around maximum amount and is kept away from the severe mechanical stress on wind turbine. In current study, in order ...
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A common method utilized in wind turbines is pitch angle control whereby via varying the angle of wind turbine blades around their own axis, power generated at high speeds of wind is held around maximum amount and is kept away from the severe mechanical stress on wind turbine. In current study, in order to control pitch angle, a control method based on using PI controller is suggested. Therefore, gains of the PI controller are regulated through combining the Firefly evolutionary algorithm and MLP neural network in such a way that the controller at its output sends a suitable controlling signal to the pitch actuator to set the pitch angle and so by varying the blades pitch angle suitably at high speeds of wind, the produced generator power remains around its nominal value. A wind turbine 5MW made by NREL (National Renewable Energy Laboratory) has been utilized based on FAST software code to simulate and analyze the results. The simulation results show that proposed method has a good performance.
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