Aerospace Science and Technology
Amir reza Kosari; Elahe Khatoonabadi; Vahid Bohlouri
Abstract
In this paper, the control of a three-axis rigid satellite attitude control system with a fractional order proportional-integral-derivative (PID) controller is investigated in the presence of disturbance and parametric uncertainties. The reaction wheel actuator with the first-order dynamic model is used ...
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In this paper, the control of a three-axis rigid satellite attitude control system with a fractional order proportional-integral-derivative (PID) controller is investigated in the presence of disturbance and parametric uncertainties. The reaction wheel actuator with the first-order dynamic model is used to control the attitude of the satellite. Uncertainties are considered on satellite moment inertia, actuator model and amplitude and frequency of external disturbances. External disturbances are modeled with two fixed and periodic parts and uncertainty is also considered on the disturbances model. The integer order controller is also used for the same conditions to compare the results with the fractional order controller. The usual Granwald-Letinkov definition is used to solve integrals and fractional order derivatives. The mean absolute of the pointing error of the satellite pointing maneuver has been selected as an objective function of the optimization problem. The controller gains in integer and fractional order are obtained by particle swarm evolution algorithm (PSO) optimization method. The performance criterion has been studied in terms of the controller time response and also in terms of the standard deviation of the mentioned uncertainties and external disturbance. The results show that the fractional order controller performs more accurate and robustness than the integer order controllers in the face of uncertainty and disturbance.
Aerospace Science and Technology
Hamed Arhami; Mohammad Mazidi Sharfabadi
Abstract
In this research, combustion modeling inside the combustion chamber of a typical turboprop engine has been investigated. The complex geometry of this combustion liner was modeled according to the technical drawings and the turbulent flow and internal combustion were simulated numerically and three-dimensionally. ...
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In this research, combustion modeling inside the combustion chamber of a typical turboprop engine has been investigated. The complex geometry of this combustion liner was modeled according to the technical drawings and the turbulent flow and internal combustion were simulated numerically and three-dimensionally. The non-premixed combustion model is used to simulate combustion and the K-ω method is used to simulate turbulent flow. This study investigated how the combustion phenomenon occurs, the internal temperature distribution, the outlet, and the wall of the combustion tube, for which comprehensive three-dimensional data were not previously available. These simulations have identified the weaknesses of the combustion tube and by eliminating these weaknesses, the problem of reducing the efficiency of several gas turbine engines has been solved. Comparison of the results of the present study with a similar numerical analysis showed that the results of this study are more in line with laboratory results. The results of the simulation of combustion pipe defects show that the combustion liner that had a welding line near the outlet had a 25% higher pressure drop than a typical combustion liner and the effective cross-sectional area of the fluid flow was reduced by 11%. The output of a repaired combustion tube is different from a typical type.
Aerospace Science and Technology
Mahdi Karami Khorramabadi; Ali Reza Nezamabadi
Abstract
In this paper, the buckling behavior of functionally graded simply supported nanocomposite beams reinforced by nano clay is studied. The specimens were prepared and the experimental tensile and buckling tests are carried out. The elastic modulus of epoxy/clay nanocomposite for functionally graded and ...
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In this paper, the buckling behavior of functionally graded simply supported nanocomposite beams reinforced by nano clay is studied. The specimens were prepared and the experimental tensile and buckling tests are carried out. The elastic modulus of epoxy/clay nanocomposite for functionally graded and uniformly distributed of nanoclay are estimated through a model based on the genetic algorithm approach. The results show that GA can be considered as an acceptable optimization research technique to identify Young’s modulus of nanocomposites with maximum accuracy. For simply supported beam, the first order shear deformation beam theory is applied for displacement field and the governing equations are derived by using Hamilton principle. The influence of nanoparticles for functionally graded and uniform distribution on the buckling load of a beam is presented. Comparison study is conducted to assess efficacy and accuracy of the present analysis. A comparison for theoretical analysis with the experimental results demonstrated the high accuracy.
Aerospace Science and Technology
Mahdi Miralam; Amir Rahni
Abstract
In multi-stage Missiles, stabilizer wings are responsible for stabilizing the Missile. The control fins located upstream of the stabilizer wings affect the flow by spinning, which influences stability as well as control. One method for resolving this problem is to design stabilizer wings with less affectability ...
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In multi-stage Missiles, stabilizer wings are responsible for stabilizing the Missile. The control fins located upstream of the stabilizer wings affect the flow by spinning, which influences stability as well as control. One method for resolving this problem is to design stabilizer wings with less affectability against the upstream flow. The present paper deals with this issue by considering multiple planar fins and grid fins. Once validation is performed, after selecting the appropriate turbulence model and choosing the planar and grid fins, the appropriate Missile model is established; then, on a model with speeds of 0.6, 0.7, and 0.8 Mach, at attack angles of 0, 2, 4, and 6 degrees, and with control fins, variation at angles of 0, 1, 3, and 6 degrees, the aerodynamic coefficients as well as the effects of the upstream stabilizer wings are investigated in pitch and roll modes at an appropriate trim angle . The obtained results indicated that the use of grid fin downstream of the control surfaces would be less affected due to its physical nature; thus, the lower capacity of the control surface would be used for control during the flight, which would significantly facilitate the process of designing.
Aerospace Science and Technology
Seyed Sam Saham; Saeed Karimian Aliabadi
Abstract
The use of urban and rural scale wind turbines that in addition to generating power can play the role of old wind turbines in arid areas will be very attractive. In this research it has been tried to first evaluate the wind energy potential in Zahedan city and then to evaluate a sample of vertical axis ...
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The use of urban and rural scale wind turbines that in addition to generating power can play the role of old wind turbines in arid areas will be very attractive. In this research it has been tried to first evaluate the wind energy potential in Zahedan city and then to evaluate a sample of vertical axis wind turbine. First, a three-dimensional semi-analytic code based on the DMST method was developed, the validation of which was studied and presented. Using this tool, the performance of the turbine in terms of power and ventilation has been investigated and in the results of this parametric study, the effect of the cone angle on the power and ventilation coefficient has been explained in detail. Based on the results of this study, it can be seen that increasing the cone angle to 20 degrees, although it reduces the power of the turbine, but does not have a significant effect on the power coefficient and at the same time causes a ventilation coefficient of about 1.6 percent. It was also observed that at a conical angle of 10 degrees and at the working point of the turbine, the output power will be 30 kW and the ventilation flow will be 30,000 m^3⁄h.
Aerospace Science and Technology
Seyed mohammad navid ghoreishi; Nabi Mehri-Khansari; Houman rezaei
Abstract
Regardless of the initiation or propagation procedure of crack in a gas turbine blade, the precise expectation of the fracture behavior, such as mixed-mode Stress Intensity Factors (SIF), plays a significant role in acquiring its operational life. Therefore, multilateral three-dimensional fracture solutions ...
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Regardless of the initiation or propagation procedure of crack in a gas turbine blade, the precise expectation of the fracture behavior, such as mixed-mode Stress Intensity Factors (SIF), plays a significant role in acquiring its operational life. Therefore, multilateral three-dimensional fracture solutions are required, including real-based mixed-mode loading (I/II/III) conditions and geometrical considerations. In this study, three-dimensional semi-elliptical crack in a gas turbine blade with various geometrical parameters and inclination angles under mixed-mode loading (I/II/III) conditions were investigated based on the employing finite element techniques and analytical procedure. In this context, the semi-elliptical crack has been considered in the critical zone of the rotating blade to achieve the effect of crack aspect ratio, rotational velocity, crack location, and mechanical properties. Fluid Solid Interaction (FSI) analysis was also performed in addition to solid functional enriched elements. Structural simulation is done at the speed of 83.776 m/s based on CFD simulation. The results indicated that Al Alloys blade shows a profitable resistance in crack propagation. Moreover, as the crack domain is near the location of x/c= 0.25 and 1.9 of crack front, the mode II SIF will be independent of rotational velocity and the blades' mechanical properties. Similarly, for the location of x/c= 1.1 in crack front, the mode III SIF is independent of rotational velocity and blades' mechanical properties.
Aerospace Science and Technology
Morteza Sharafi; Nasser Rahbar; Ali Moharrampour; Abdorreza Kashaninia
Abstract
This study proposes a new non-linear guidance law for a Falcon 9 missile booster landing's terminal phase using a non-linear vectorized high expansion method. For this purpose, At first, the dynamic modeling of the landing problem is presented, assuming mass, gravity, and density are variables. Then, ...
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This study proposes a new non-linear guidance law for a Falcon 9 missile booster landing's terminal phase using a non-linear vectorized high expansion method. For this purpose, At first, the dynamic modeling of the landing problem is presented, assuming mass, gravity, and density are variables. Then, sensitivity variables are extracted using the vectorized high order expansion method and assuming the parameters constant. Then, the guidance law is extracted to update the path and optimal commands using sensitivity variables. The path and commands of the near-optimal guidance are extracted online using the proposed guidance law. Considering initial deviations, the guidance law performance in simulations are studied using a combination of various initial deviations. The results shown as charts and numerical values of errors indicate that the landing point errors are insignificant, and the vectorized high order expansion method has a desirable performance for the reusable booster's vertical landing.
Aerospace Science and Technology
Hossein Shadmehr; Sajad Ghasemloo; Hamid Parhizkar
Abstract
In this article, the idea of building a supersonic wind tunnel has been provided that uses a high-pressure steam flow of a combined cycle power plant. This has been investigated by CFD method. Using the plant's output steam as a high-pressure source can be used in the ejector to create supersonic airflow ...
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In this article, the idea of building a supersonic wind tunnel has been provided that uses a high-pressure steam flow of a combined cycle power plant. This has been investigated by CFD method. Using the plant's output steam as a high-pressure source can be used in the ejector to create supersonic airflow in the test chamber. For this purpose, first, the numerical model has been validated in comparison with the previous numerical and experimental results. The numerical model used is the viscous compressible flow, which is performed by the k-ω-SST turbulent modeling of the turbulence model. All calculations are performed in ANSYS-FLUENT software. After validating the numerical process, various geometries have been proposed to achieve the ultrasonic secondary flow and each structure is examined numerically separately in a range of functional conditions. Through trial and error method and looking at the achievements of previous research, in a very long process and by testing several different structures, a suitable structure has been obtained to achieve the supersonic testing chamber. This structure has been studied parametrically under different functional conditions. It has been shown that the proposed structure can generate an ultrasonic flow in an acceptable range of power plant steam flow and pressure. This structure has been proposed for the first time in the literature in this field, and in no previous research has such a structure been proposed. Access to the ultrasonic secondary flow is also a major innovation of this research.
Aerospace Science and Technology
Mahdi Amani Estalkhkuhi; Jafar Roshanian
Abstract
In this paper, a multi-input/multi-output sliding controller is proposed and analyzed for a quad tilt-wing unmanned aerial vehicle (QTW-UAV). The vehicle is equipped to do take-off and landing in vertical flight mode and is capable of flight over long distances in horizontal flight mode. The full dynamic ...
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In this paper, a multi-input/multi-output sliding controller is proposed and analyzed for a quad tilt-wing unmanned aerial vehicle (QTW-UAV). The vehicle is equipped to do take-off and landing in vertical flight mode and is capable of flight over long distances in horizontal flight mode. The full dynamic model of the vehicle is originated from the Newton-Euler formulation. For developing the controller, a set of integral type sliding surfaces is selected and it is necessary to mention that in this approach, there isn't any linearization during controller design. Simulation has been conducted for a nonlinear, multivariable model that includes uncertain parameters and in the presence of pitch angle measurement noise and pitch moment disturbance. For verification, the proposed controller is compared with linear based controller design simulation. Results exhibit that the proposed controller is robust in the face of uncertainties, noise and disturbance and meets performance demands with control inputs of low amplitude.
Aerospace Science and Technology
Sajad Ghasemlooy; mahsa dehnamaki; Hamid Parhizkar
Abstract
The calculation of aerodynamic heating is one of the most important steps in designing high speed flying bodies, especially reentry bodies. Because ignoring that, it can damage the thermal protection system and cut off the radar connections to the reentry capsule. Due to the high speed of the capsule ...
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The calculation of aerodynamic heating is one of the most important steps in designing high speed flying bodies, especially reentry bodies. Because ignoring that, it can damage the thermal protection system and cut off the radar connections to the reentry capsule. Due to the high speed of the capsule and the lack of a material medium, the radiation heat transfer rate is important in comparison to the convection heat transfer rate of the displacement in determining the total thermal flux, and ignoring it in the calculations caused many errors in the determination of the total heat flux . In this paper, various parameters affecting the heat transfer rate of the nose of the reentry capsule have been investigated. To calculate the capsule nose radiation, a theoretical method is presented which is compared with the reference simulation results to confirm its correctness. In this simulation, the heat transfer rate of the Apollo4 capsule has been investigated. Due to the low optical thickness of the model, the DO radiation model is used to simulate CFD. This simulation was carried out using Fluent software version 16 and solved with a laminar flow of gray gas and non-gray gas. The results show that the radiation heat transfer rate in non-gray gas mode is lower error than the gray gas state, and it is also observed that at high altitudes, the radiation transfer rate is 80% of the total heat transfer rate.
Aerospace Science and Technology
Mohammad Hossein Bayat; Mohammad Shahbazi; Bahram Tarvirdizadeh
Abstract
The use of Unmanned Aerial Vehicles (UAVs) with different features and for a variety of applications has grown significantly. Tracking generic targets, especially human, using the UAV's camera is one of the most active and demanding fields in this area. In this paper we implement two vision-based tracking ...
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The use of Unmanned Aerial Vehicles (UAVs) with different features and for a variety of applications has grown significantly. Tracking generic targets, especially human, using the UAV's camera is one of the most active and demanding fields in this area. In this paper we implement two vision-based tracking algorithms to track a human by using a 2D gimbal which can be mounted on UAVs. To ensure smooth movements and reduce the effect of common jumps on the trackers output, the gimbal motion control system is equipped with a Kalman filter followed by a proportional-derivative (PD) controller. Various experimental tests have been designed and implemented to track a human. The evaluation results show success in tracking the high speed movements with one of the algorithms and high accuracy in tracking the challenging movements in the other algorithm. Also in both methods, the tracking computation time is short enough and suitable for real-time implementation. The favorable performance of both algorithms indicate the ability of designed system to be implemented on the UAVs for practical applications.
Aerospace Science and Technology
Mohammad Reza Salimi; Mohsen Rostami; Amir Hamzeh Farajolahi; Morteza Ghanbari
Abstract
In this paper, flow and heat transfer inside a helicopter shell and tube heat exchanger is simulated in three dimensions. This converter consists of a shell with 90 U-shaped tubes inside. For further heat transfer, the tubes were simulated and compared once without fins and again with fins, which are ...
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In this paper, flow and heat transfer inside a helicopter shell and tube heat exchanger is simulated in three dimensions. This converter consists of a shell with 90 U-shaped tubes inside. For further heat transfer, the tubes were simulated and compared once without fins and again with fins, which are produced longitudinally and integrally with the tube body. The current flowing in the shell is MIL-PRF 23699 oil and the flowing fluid in the tubes is JP-4 fuel. These two fluids flow in opposite directions and exchange heat with each other. Using Aspen software, the design is done in such a way that the heat exchanger has minimum length and weight to have a better and higher effect on the efficiency of the helicopter. To investigate the effect of tube geometry and oil mass flow on the heat transfer between fuel and oil, simulation has been performed in ANSYS Fluent program. In this simulation, a part of the whole heat exchanger is selected as the geometry and the effect of changing the geometry of the tubes, mass flow of fuel and oil on the heat transfer coefficient, Colburn coefficient, coefficient of friction and their ratio, and outlet temperature changes are investigated. The results of this simulation show that the heat transfer rate between fuel and oil for a heat exchanger with finned tubes is about 11% higher than without a fin. Also, reducing the mass flow of oil entering the shell increases the efficiency of the heat exchanger.
Aerospace Science and Technology
Hossein Faveadi; Ali R. Davari; Farshad Pazooki; Majid Pouladian
Abstract
Flight simulation is a powerful and usefull instrument in design, testing, evaluation and validation of aircrafts; The results of aerolastic simulation along with rigid simulation can be used in the many areas of designs, such as modification or optimization, stability analysis and evaluating field test ...
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Flight simulation is a powerful and usefull instrument in design, testing, evaluation and validation of aircrafts; The results of aerolastic simulation along with rigid simulation can be used in the many areas of designs, such as modification or optimization, stability analysis and evaluating field test data; It can be said that the use of simulation in the fields of design and optimization, especially during the initial and detailed design, should be considered more than other fields; In this research, by use of simulation, the effect of some design parameters such as slenderless ratio, maneuvering acceleration, propulsion curve, natural frequency of the structure, aerodynamic load distribution , etc. On issues such as flight and tracking behavior, stability and collision accuracy, has been examined; In cases such as: evaluating the initial error or veviation of the thurst vector or its curve, rolling speed, tracking of control commands, etc. aerolastic simulation gives a more realistic output compared to rigid simulation; Further more in cases such as investigating the effect of aerodynamic load distribution or stiffness ans and mass distribution, only aerolastic simulation is able to respond. Accordingly, the main orientation of this research is to develop an approach with acceptable accuracy and speed in order to simulate elastic projectiles in order to achieve some of the mentioned goals; However, due to the wide range of effective parameters and their interaction, in this study, only the role of thrust and body rigidity has been examined.
Aerospace Science and Technology
Ali Khoshnejad; Reza Ebrahimi; Golamhosein Pouryossefi
Abstract
Aero-engine entrance conditions are not always ideal and, for various reasons, inlet distortion may occur and cause inlet blockage and reduction of compressor performance. The aim of this study was to numerically simulate the effects of plasma actuators on the enhancement of low-speed axial compressor ...
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Aero-engine entrance conditions are not always ideal and, for various reasons, inlet distortion may occur and cause inlet blockage and reduction of compressor performance. The aim of this study was to numerically simulate the effects of plasma actuators on the enhancement of low-speed axial compressor rotor performance under radial inlet distortion. First, compressor performance under radial inlet distortion with 15% and 20% blockage and theirs destructive effects on stall margin was investigated. Then, the effect of plasma actuators on rotor loss subjected to inlet distortion was investigated, using an algebraic model based on the plasma actuators physics in form of body force distribution in Naiver-Stokes equations. The results show that radial inlet distortion causes decreasing stall margin of the compressor. In addition, according to the findings, applying plasma actuators boosts the flow momentum behind the distortion screen and reduces the blockage of the rotor tip region, leading to decreasing losses. Furthermore, at 15% blockage, the plasma actuators caused to increase the stall margin from -11% to -5% versus the rotor in clean condition.
Aerospace Science and Technology
Ali Arabian Arani; S.H. Jalali Naini; Mohammad Hossein Hamidi Nejad
Abstract
This study presents the miss distance analysis of the first-order explicit guidance law due to seeker noise using the adjoint method. For this purpose, linearized equations are utillized and the adjoint model is developed. Then the first-order equations are obtained and converted into nondimensional ...
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This study presents the miss distance analysis of the first-order explicit guidance law due to seeker noise using the adjoint method. For this purpose, linearized equations are utillized and the adjoint model is developed. Then the first-order equations are obtained and converted into nondimensional ones. The analysis is carried out for different values of the power of the alpha function, defined as the time decrease rate of the zero-effort miss distance to unit control input. The unity power gives the first-order optimal guidance strategy, minimizing the integral of the square of the commanded acceleration during the total flight time.The seeker and control system is assumed as a fifth-order binomial transfer function. Due to computational error and stability consideration, the effective navigation ratio is kept constant for very small time-to-go until intercept, which its effect on the miss distance is also investigated. Finally, approximate formulas are obtained using curve fitting method for rms miss distance due to seeker noise.
Aerospace Science and Technology
Amir reza Kosari; Ehsan Abbasali; Majid Bakhtiyari; Hamed Golpour
Abstract
The main purpose of this article is to examine the periodic coupled orbit-attitude of a satellite at restricted three body problem considering both primaries oblateness perturbations. The proposed model was based on a simplified coupled model meaning that the time evolution of the orbital state variables ...
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The main purpose of this article is to examine the periodic coupled orbit-attitude of a satellite at restricted three body problem considering both primaries oblateness perturbations. The proposed model was based on a simplified coupled model meaning that the time evolution of the orbital state variables was not a function of the attitude state variables. Since, the problem has no closed-formed solution, and the numerical methods must be used, so the problem can have different periodic or non-periodic responses to the initial conditions. The initial guess vector of the coupled model’s states was introduced to achieve the optimal initial conditions leading to the periodic responses, and then the P-CR3BP coupled orbit-attitude correction algorithm was proposed to correct this initial guess. Since, the number of periodic solutions is restricted; the suitable initial guess vector as the inputs of the coupled orbit-attitude correction algorithm increases the chances of achieving more accurate initial conditions. The initial guess of orbital states close to the initial conditions of the P-CR3BP periodic orbit, along with initial guess vector of attitude dynamics states with Poincaré mapping was suggested as the suitable initial guess vector of the coupled model.
Aerospace Science and Technology
Mahdi Azizi; Alireza Jahangirian
Abstract
To keep pace with current trends in the wind industry, this paper aims at the improvement of the annual energy production of a horizontal axis wind turbine by aerodynamic optimization of blades at the wind conditions of the Manjil site. To achieve this goal, the Riso wind turbine, whose characteristics ...
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To keep pace with current trends in the wind industry, this paper aims at the improvement of the annual energy production of a horizontal axis wind turbine by aerodynamic optimization of blades at the wind conditions of the Manjil site. To achieve this goal, the Riso wind turbine, whose characteristics are publicly available, is selected, and its twist angle and chord length distributions along the blades are optimized. The blade element momentum theory with appropriate corrections is used to predict the turbine output power. The genetic algorithm optimization tool, and Weibull probability density function, for wind regime representation, are also utilized in this work. Optimization results show a 9.4% and 11.6% increase in annual energy production, respectively, for the blade with optimal twist angle and the blade with optimal chord length and twist angle distributions. Finally, the superiority of selecting annual energy production as the objective function is assessed in comparison with other objective functions.
Aerospace Science and Technology
Alireza Akbari; Sahar Noori; Payman Spahvand
Abstract
The main application of dynamic coefficients is in the flight path simulation and autopilot design of flying objects. This paper reveals a general process for calculating the roll damping coefficient of a typical airship. The process presented in this article has a step-by-step path that can be used ...
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The main application of dynamic coefficients is in the flight path simulation and autopilot design of flying objects. This paper reveals a general process for calculating the roll damping coefficient of a typical airship. The process presented in this article has a step-by-step path that can be used to calculate the roll dumping coefficient of all projectiles and flying objects. The method applied in this paper is fully numerical and the dynamic coefficient will be extracted from the Fluent software using the moving reference frame (MRF) techniques. In this process, first, the roll moment coefficient is extracted from the fluent using the moving reference frame technique, and then the roll damping coefficient will be calculated using some relations presented in this paper. At the beginning of the present work, the general process of calculating dynamic coefficients is discussed. This process is then used to calculate the dynamic coefficient of a typical geometry. The results of the present work and the process of calculating this coefficient, which is fully discussed in this article, can be used to calculate this coefficient in other flying objects with similar geometry. In order to validate the present article, the results of the present work are validated with the results of another article. Acceptable agreement of the results of the present work with references, proves the correctness of the process presented in this paper for calculating this dynamic coefficient.
Aerospace Science and Technology
Mahdi Fakoor; Hamidreza Heidari; Behzad Moshiri; Amir reza Kosari
Abstract
In this study, Adaptive Network-Based Fuzzy Inference System (ANFIS) is presented with sensor data fusion approach to estimate satellite attitude. The active sensors are sun and earth sensors. Satellite attitude dynamic, including attitude quaternion and angular velocities are estimated simultaneously ...
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In this study, Adaptive Network-Based Fuzzy Inference System (ANFIS) is presented with sensor data fusion approach to estimate satellite attitude. The active sensors are sun and earth sensors. Satellite attitude dynamic, including attitude quaternion and angular velocities are estimated simultaneously utilizing the measured values by the sensors. The Extended Kalman Filter (EKF) is employed to verify and evaluate the efficiency of the presented method. Additionally, the neural networks with Radial Basis Function (RBF) and Multi-Layer Perceptron (MLP) are also designed to prove the superiority of the proposed ANFIS network among the smart methods of sensor data fusion for satellite attitude estimation. Root Mean Square Error (RMSE) as a numerical criterion and graphical analysis of residues are utilized to evaluate the simulation results. The simulations confirm that the obtained estimations from ANFIS network have more accuracy in modeling of nonlinear complex systems compared to EKF, MLP and RBF networks. In general, using intelligent data fusion, especially ANFIS, reduces attitude estimation error and time in comparison to the classical EKF method.
Aerospace Science and Technology
Hadi Hamedani; Ahmad Mamandi
Volume 14, Issue 2 , October 2021, , Pages 30-51
Abstract
In this paper, the effects of different rotational speed functions in the elastic-plastic deformation and stress analysis of a rotating annular thin disk of functionally graded material (FGM) in Reddy model is studied using the analytical and FEM methods. In this regard, differential equations governing ...
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In this paper, the effects of different rotational speed functions in the elastic-plastic deformation and stress analysis of a rotating annular thin disk of functionally graded material (FGM) in Reddy model is studied using the analytical and FEM methods. In this regard, differential equations governing dynamic equilibrium for displacements and stresses in the elastic region of the FGM rotating disk have been derived using the theory of elasticity in plane stress condition and have been solved by the shooting method. Then, the equations governing the distribution of plastic radial and circumferential stresses on the disk have been extracted using the Prandtl-Reuss theory of plasticity and based on the Ludwig hardening law in conjunction with the von Mises yield criterion. Also, by modeling the annular thin disk in the environment of finite element software ANSYS, the results obtained from the elastic analytical solution and the finite element numerical solution have been compared to each other and to the results reported in the literature for specific cases and validated accordingly. The effects of variation of the disk geometric parameters, functionally graded material power index as well as different type of the time-dependent rotational speed functions such as the constant speed, exponential, and accelerated/decelerated linear, quadratic, and square root functions on the elastic behavior of the disk and distribution of radial displacement, and also distribution of radial, circumferential, and shear stresses on the disk have been studied. Moreover, the results of plastic analysis have been presented for distribution of radial and circumferential stresses on the disk.
Aerospace Science and Technology
Ahmad Sharafi
Volume 14, Issue 2 , October 2021, , Pages 52-65
Abstract
In the present study, the aerodynamic performance of the ducted fan is investigated using the surface vorticity method and the lifting line theory. In previous research, to consider the effects of the duct, most of the parameters derived from empirical tests or computational fluid dynamics. Our goal ...
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In the present study, the aerodynamic performance of the ducted fan is investigated using the surface vorticity method and the lifting line theory. In previous research, to consider the effects of the duct, most of the parameters derived from empirical tests or computational fluid dynamics. Our goal is to present a new method for considering the effects of the duct on the fan enclosed in a duct. In this method, the lift and drag coefficients are only input parameters. The present method requires considerably less computational time than CFD methods. Also, the aerodynamic optimization of fan blades geometry has been carried out using particle swarm optimization method (PSO) to achieve the optimum blade geometry and the maximum output power. The results of this method are in excellent agreement with experimental data in references. By optimizing the geometry of the blade, the output power of ducted fan increased 10 percentage in comparison to ducted fan with old blade geometry.
Aerospace Science and Technology
M.E. Golmakani; M. Moravej; M. Sadeghian
Volume 14, Issue 2 , October 2021, , Pages 66-79
Abstract
In this paper, the nonlinear thermal buckling of moderately thick functionally graded cylindrical panels is analyzed based on the first-order shear deformation theory (FSDT) and large deflection von Kármán equations. The highly coupled nonlinear governing equations are solved using the ...
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In this paper, the nonlinear thermal buckling of moderately thick functionally graded cylindrical panels is analyzed based on the first-order shear deformation theory (FSDT) and large deflection von Kármán equations. The highly coupled nonlinear governing equations are solved using the combination of dynamic relaxation approach with the finite-difference discretization method at various boundary conditions. The material properties of the constituent components of the FG shell are considered to vary continuously along the thickness direction based on simple power-law and Mori-Tanaka distribution methods, separately. The critical thermal buckling load is considered based on the thermal load-displacement curve derived by solving the incremental form of nonlinear equilibrium equations. In order to consider the accuracy of the present results, a comparison study has been carried out. The effects of the boundary conditions, rule of mixture, grading index, radius-to-thickness ratio, length-to-radius ratio and panel angle are studied on the thermal buckling loads. It is observed from the results that in high values of radius-to-thickness ratios, there is no difference between the values of critical buckling temperature differences for linear and nonlinear distributions.
Aerospace Science and Technology
Hamed Alisadeghi; Parsa Abbasrezaee
Abstract
In this article, we analyze the existing de-orbiting mechanisms in the world and analyze different types of these mechanisms for Nano satellites, also known as CubeSats. Moreover, a new passive and efficient design of the de-orbiting mechanism for the CubeSats have been proposed. Utilizing de-orbiting ...
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In this article, we analyze the existing de-orbiting mechanisms in the world and analyze different types of these mechanisms for Nano satellites, also known as CubeSats. Moreover, a new passive and efficient design of the de-orbiting mechanism for the CubeSats have been proposed. Utilizing de-orbiting mechanisms are important in Nano satellites or CubeSats to prevent production of space debris in LEO (low-earth orbit), and in NASIR-1 CubeSat, Sail Drag method was used to do so. In this method, the satellite is deorbited using passive two-sided de-orbiting approach in 1.7 years on average, or less than a maximum of 2 years. Software analysis is used to calculate membrane size and the required boom mechanisms in LEO, 600 km from the earth’s surface. Drag sail is designed using software and the prototype as well as the final version for engineering model are made and tested. The passive two-sided sail drag design of NASIR-1 is a more efficient mechanism compared to active, four-sided models in terms of volume, weight and the required electrical power and it offers a larger available externa surface on CubeSat’s surfaces.
Aerospace Science and Technology
Majid Sedghi; Rouhollah Khoshkhoo
Abstract
This research aims to numerically investigate the efficiency of the plasma actuator in a small wind turbine. The studies were conducted on a domestic wind turbine with a diameter of 1.93 m and the Suzen-Huang model was employed to simulate the DBD plasma actuator. In this research, first, a wind turbine ...
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This research aims to numerically investigate the efficiency of the plasma actuator in a small wind turbine. The studies were conducted on a domestic wind turbine with a diameter of 1.93 m and the Suzen-Huang model was employed to simulate the DBD plasma actuator. In this research, first, a wind turbine without the plasma actuator was simulated at different tip speed ratios. Then, the DBD plasma actuator was activated at a tip speed ratio of 4.35, and changes in the power output, torque distribution, and surface streamlines were studied. The results indicate with an increase in the power of the plasma actuator, the separation point moved away from the leading edge, the span-wise flows were reduced, and the turbine power output increased. The performance of the plasma actuator is varied along the wind turbine blade length. For the radii r/R=0.4-0.95, a difference in the generated torque can be observed for active and inactive plasma modes, and the plasma actuator did not significantly affect the power output in other sections. The maximum increase in torque due to the plasma actuator has occurred at the radii r/R=0.5-0.7. In these regions, the distance between the separation point and the plasma actuator location is about 0.2 times the chord length of the airfoil.
Aerospace Science and Technology
Amirali Nikkhah; Hoseyn Mojarrab; Fatemeh Mojarrab; Reza Zardashti
Abstract
The design of a ground collision avoidance system for an airplane based on optimal control theory is presented in this paper. A control system is designed by linear quadratic tracker to track desired Euler angles of airplane. The system independent of 3 dimensional maps, works by using a forward looking ...
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The design of a ground collision avoidance system for an airplane based on optimal control theory is presented in this paper. A control system is designed by linear quadratic tracker to track desired Euler angles of airplane. The system independent of 3 dimensional maps, works by using a forward looking camera. In addition, the obstacle is analyzed by digital image processing techniques. An optimal flight control system based on discrete-time linear quadratic tracker is designed, to fly over or pass obstacles like mountains automatically.
