Wall correction for a supercritical airfoil in the low speed wind tunnel
Mehran
Masdari
Aerospace Department, Faculty of New Sciences and Technologies, University of Tehran
author
Mohsen
Bashna
Aerospace Department, Faculty of New Sciences and Technologies, University of Tehran
author
Arshia
Tabrizian
Aerospace Department, Faculty of New Sciences and Technologies, University of Tehran
author
text
article
2018
per
One of the most important reasons for the difference between the results of wind tunnel experiments and flight conditions is the effect of the wind tunnel walls. The walls in the test section affect the air flow in the longitudinal and lateral directions, causing a difference between the measured values and the free stream. In this paper, the effects of blockage associated with an supercritical airfoil in a steady state for different attack angles have been investigated and a specific method for correcting the effects of walls has been developed. The Experiments were carried out in a low speed and closed circuit wind tunnel at a speed of 30 m / s and Reynolds No. equal to 600,000 using the pressure distribution measurement on the model and the tunnel wall. Using the pressure distribution on the tunnel wall, the flow field around the model with source and sink potential was estimated approximately. Then, using a rapid algorithm, the distribution of these potentials was calculated along the central line of the tunnel and finally corrected by calculating the effects of blockage, pressure distribution on the model, dynamic pressure and measured aerodynamic coefficients. Also, modified aerodynamic coefficients were compared with each other separately. The results obtained from these two methods differed slightly in relation to the attack angles, with the highest difference of 7% in the angle of attack of 20 degrees. Also, the developed methods indicated the accuracy of the corrections on the aerodynamic coefficients.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
7
22
http://www.astjournal.ir/article_31743_d41d8cd98f00b204e9800998ecf8427e.pdf
Aerodynamic and noise simulation of compressible supersonic gas flow exiting from tube
Sepideh
Roshdi
دانشجوی دکتری / دانشگاه علم و صنعت ایران
author
Rahman
Mahdiani
سازمان صنایع دفاع
author
Alireza
Mostafavi
defense industries organization
author
Mortezai
Razaghi
سازمان صنایع دفاع
author
Hossein
Ashrafi
عضو هیات علمی / دانشگاه کاشان
author
text
article
2018
per
Simulation of supersonic compressible gas flow has been investigated while exiting from 7.62 mm diameter tube in the axis-symmetric geometry. Density-based solver and adaptive dynamic mesh methods were applied based on static pressure gradient. Simulations have been carried out using inviscid and k-ɛ turbulence models. Time of first, second, and main flow shock waves and their progress were also investigated. Existing experimental Schlieren shadowgraphs were compared with density contours of simulations and static pressure results within the shock waves were also compared with the results of literature and good agreements have been achieved. After verification, simulation results have been applied in order to extract sound pressure level values using Ffowcs-Williams and Hawkins (FWH) model. Sound pressure receivers have been located in1, 2,6,10 and 15 m far from the sound source and sound pressure levels have been obtained and compared at the three different times. Results were in good agreement with test data of existing literature. Maximum sound pressure level was obtained in the time of 0.58 millisecond equaling 119 dB. Simulations results showed that changing viscous model from inviscid to k-ɛ turbulence model had an insignificant effect on the noise values.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
23
34
http://www.astjournal.ir/article_31764_d41d8cd98f00b204e9800998ecf8427e.pdf
Experimental determination of PE regression rate with an axial GOX injection
Mohammad Mahdi
Heydary
عضو هیات علمی / دانشگاه صنعتی مالک اشتر
author
Nooredin
Ghadiri Massoom
دانشجوی دکتری / دانشگاه صنعتی مالک اشتر
author
text
article
2018
per
In this paper, a hybrid motor performance with high density poly ethylene (HDPE) as fuel and gaseous oxygen (GOX) as oxidizer was studied. Oxidizer was injected into nozzle with an axial injector. Effect of parameters such as mass flux, combustion chamber pressure, and distance from grain lead were studied through tests and by means of data reduction techniques. Besides, effect of utilizing pre-combustion chamber was studied. It was shown that using pre-combustion chamber helps to have an even regression in axial direction. In this case, regression rate was independent from axial location from grain lead. Dependency of regression rate to combustion chamber pressure was also determined which showed a good agreement with available empirical data. Finally, a classic regression rate relation for poly ethylene was determined in terms of total mass flux and combustion chamber pressure.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
35
46
http://www.astjournal.ir/article_31765_d41d8cd98f00b204e9800998ecf8427e.pdf
Approximate miss distance formulas of proportional navigation due to time delay based on worst case analysis
Ali
Arabian Arani
دانشجوی دکتری / دانشکدة مهندسی مکانیک، دانشگاه تربیت مدرس
author
Seyed Hamid
Jalali Naini
عضو هیات علمی / دانشکدة مهندسی مکانیک، دانشگاه تربیت مدرس
author
text
article
2018
per
In this paper, the effect of system time delay on the miss distance of proportional navigation guidance law is studied for high-order binomial guidance and control systems. For this purpose, a linearized model is utilized in one dimension. The normalized miss distance due to heading error (HE), step, ramp, and parabolic target maneuvers, and seeker noise is computed using normalized adjoint equations. The glint, range-independent, and (semi-) active range-dependent noises are considered for the seeker, and the results are verified by straight-forward method. Moreover, the effects of system time lag, system time constant, effective navigation ratio, system order up to 30 in proportional navigation miss distance are also investigated. An extremum effective navigation ratio is also obtained to minimize the worst case miss distance with respect to the final time. Furthermore, approximate miss distance formulas are presented based on worst case analysis on final time using curve fitting for mentioned miss distance sources. Finally, the approximate formulas of steady state nondimensional coefficients due to seeker noise in terms of effective navigation coefficient, for example for system orders of 5 and 10, are obtained.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
47
62
http://www.astjournal.ir/article_31785_d41d8cd98f00b204e9800998ecf8427e.pdf
Closed form position of airborne targets in new design of geometric constrained problem by bearing measurements
Majid
Khanlarzadeh
دانشجوی دکتری / دانشکدة هوافضا، دانشگاه خواجه نصیرالدین طوسی
author
Kamal
Mohamedpour
عضو هیات علمی / دانشکدة برق، دانشگاه خواجه نصیرالدین طوسی
author
text
article
2018
per
Positioning involves a wide range of military and industrial applications. In a positioning based on directional measurement, the transmitter's position is the intersection of the hypothetical orientation lines that send out the sensors to the transmitter. In the absence of noise, the location of these lines will be unique. But in reality, existing noise causes uncertainty in measurements and positioning. So far, various approaches have been introduced for orientation measurement based positioning. Most of these methods are based on numerical algorithms and the traditional maximum likelihood in order to estimate the optimal target position. These methods are equivalent to minimizing the total measurement errors by assuming Gaussian noise. Although TML is accurate, but due to the use of a recursive numerical algorithm, when the noise measurements are large or the geometry of the problem is undesirable, it causes a divergence of algorithm. Because of the use of numerical algorithms, these methods do not have a mathematical closed form for the answer. In addition to these methods, limited efforts are made to solve the problem and extract the closed form answer based on the geometric properties of the problem, most notably the Stansfield method. This algorithm is based on the assumption that the Gaussian noise is small and that the transmitter's approximate distance from the sensors is known. In this paper, attention is paid to the geometric properties of the problem in order to extract the closed form answer. But the assumption of the small Gaussian noise and the approximate distance between the transmitter and the sensors are not required. In most papers, the response of the TML algorithm as a benchmark has been compared in order to determine the precision of the proposed method. In this paper, it is shown in several scenarios that the proposed algorithm has a lower RMSE error than the TML, in addition to providing a mathematical closed form answer.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
63
71
http://www.astjournal.ir/article_31786_d41d8cd98f00b204e9800998ecf8427e.pdf
Real time fuzzy model predictive motion cueing design
Abolfath
Nikranjbar
عضو هیات علمی / دانشکدة مهندسی مکانیک و هوافضا، دانشگاه آزاد اسلامی، واحد علوم و تحقیقات
author
text
article
2018
per
Endeavor achieving as much as realistic perception of motion in motion cueing design are shifted towards utilizing the general nonlinear models of the motion systems. However, this approach is computationally more demanding. Hence, using efficient computational algorithms are essential to fulfill the requirements of high computing speed and accuracy without any interruption in real-time operations. Takagi - Sugeno fuzzy system as a major sector of soft computing characterized by effectively dealing with nonlinear processes, high computational speed, and easy implementation is used to approximate the nonlinear inverse kinematic of the motion system model by fuzzy interpolation of the set of linear sub models. The augmented linear parameter varying motion cueing model is constructed incorporating the fuzzy approximated inverse kinematics of the motion system along with the human perception of motion. The complete motion cueing model is computed using real-time model predictive control approach considering all physical constraints. The results of simulation show remarkable improvements in terms of less and smooth movements of actuators, hence much efficient use of motion system’s workspace compared to its general nonlinear counterpart, which reveals an effective alternative in real-time applications.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
73
87
http://www.astjournal.ir/article_31787_d41d8cd98f00b204e9800998ecf8427e.pdf
Hazard rate behavior of interior ballistics performance based on optimal reliability modeling
Mehdi
Karbasian
عضو هیات علمی / دانشکدة مهندسی صنایع، دانشگاه صنعتی مالک اشتر
author
Hamid
Dalaeli
دانشجوی دکتری / دانشکدة مهندسی صنایع، دانشگاه صنعتی مالک اشتر
author
Bijan
Khayambashi
عضو هیات علمی / دانشکدة مهندسی صنایع، دانشگاه صنعتی مالک اشتر
author
Ommolbanin
Yousefi
عضو هیات علمی / دانشکدة مهندسی صنایع، دانشگاه صنعتی مالک اشتر
author
text
article
2018
per
The field of ballistic protection assessment is challenging due to the need of satisfying high precision requirements with a limited sample size. Identifying the probability of perforation at a specified projectile velocity is the most common way to quantify the ballistic resistance of a given protection structure. Recently several techniques have been developed for this purpose to assess perforation for all possible velocities. The main drawback of these techniques is the use of the normality assumption under which perforation velocities are expected to follow a Gaussian normal distribution where . Accordingly, any parameter of interest is estimated using the characteristic identified Gaussian distribution. In this work, Interior ballistic data obtained from real tests of intelligence mortar bomb and each selected life distributions applied to the external ballistic data, using the method of maximum likelihood to estimate the model parameters. Then, estimation results from the models compared and evaluated. Different criteria for assessing the goodness of each model investigated. The objective is to identify criteria that can distinguish which life distribution produces the best estimate of the performance of a particular armor model. Another objective of this work is to apply optimal model for obtaining different probabilities, investigating mission reliability, and studying hazard rate behavior of ballistic performance. Lifetime distributions are considered and the Mixture Normal distribution provided optimal results to assess and compare the estimations of ballistic performance data.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
89
101
http://www.astjournal.ir/article_31788_d41d8cd98f00b204e9800998ecf8427e.pdf
Energy and exergy analyses of a proton exchange membrane (PEM) electrolyzer integrated with concentrating solar plant
Faezeh
Moradi Nafchi
دانشجوی کارشناسی ارشد / گروه مهندسی مکانیک، دانشکدة فنی و مهندسی، دانشگاه اصفهان
author
Ebrahim
Afshari
عضو هیات علمی / گروه مهندسی مکانیک، دانشکدة فنی و مهندسی، دانشگاه اصفهان
author
Ehsan
Baniasadi
عضو هیات علمی / گروه مهندسی مکانیک، دانشکدة فنی و مهندسی، دانشگاه اصفهان
author
text
article
2018
per
Hydrogen production using PEM electrolysers is an effective method to produce a renewable energy resource. Also, the hydrogen and oxygen generated by electrlyzer can be used in a fuel cell of drones. Thermodynamic analysis of PEM electrolyzer is essential to identify key losses and to optimize the performance of the electrolyzer. In this article, the process of water electrolysis in a PEM electrolyser integrated with concentrating solar plant to produce power and hydrogen is studied and the effect of solar intensity, current density and other operating parameters on the rate of the hydrogen production is investigated. The results indicate that increase of current density and consequently the rate of the hydrogen production leads to increase of voltage and decrease of energy and exergy efficiency of the electrolyser. Also, increase of temperature, decrease of pressure and thickness of nafion membrane lead to decrease of voltage and improve the performance of electrolyser. Increase of solar intensity by 145 percent leads to increase of the rate of hydrogen production by 110 percent and decrease the exergy and energy efficiency of electrolyser by 13.8 percent.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
103
115
http://www.astjournal.ir/article_31789_d41d8cd98f00b204e9800998ecf8427e.pdf
Numerical prediction of elastic properties of carbon nanotube reinforced composites using multi-scale method
Sina
Alemi Parvin
کارشناس ارشد / گروه مهندسی مکانیک طراحی کاربردی، دانشگاه آزاد اسلامی واحد تبریز
author
Asghar
Mohammadpour Fattahi
عضو هیات علمی / گروه مهندسی مکانیک طراحی کاربردی، دانشگاه آزاد اسلامی واحد تبریز
author
text
article
2018
per
The main goal of this research is study on longitudinal elastic modulus of nanocomposites reinforced with Zigzag and Armchair carbon nanotubes in different volume fractions and aspect ratios with finite element simulation. A three-phase volumetric element was used to model the behavior of the nanocomposite and used nonlinear spring strain elements to model the interfacial phase interface and the effective force between the nanotube and the resin based on the Lenard-Jones potential. After evaluation and validation of the model, the elastic modulus and Poisson coefficient were extracted from nanocomposites reinforced with Zigzag and Armchair carbon nanotubes in different volume fractions and aspect ratios. By increasing the nanotube volume fraction and aspect ratio, the amount of the elastic modulus of the composite increases. In the same aspect ratio and volume fraction, the modulus of elastic composites reinforced with armchair nanotubes and the Poisson coefficient of composites reinforced with zigzag nanotubes is higher. Also, the results of the study showed that the elastic modulus of the composite is independent of the elastic modulus of intermediate phase.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
117
128
http://www.astjournal.ir/article_31790_d41d8cd98f00b204e9800998ecf8427e.pdf
Optimum design of launch pad structure for ship launched launch vehicle, with simulated annealing algorithm
Asghar
Mahdian
عضو هیات علمی / مجتمع دانشگاهی مکانیک و هوافضا، دانشگاه صنعتی مالک اشتر
author
Masood
Basiri
دانشجوی دکترا / مجتمع دانشگاهی مکانیک و هوافضا، دانشگاه صنعتی مالک اشتر
author
Bizhan
Abdi
دانشجوی دکترا / مجتمع دانشگاهی مکانیک و هوافضا، دانشگاه صنعتی مالک اشتر
author
text
article
2018
per
Design, analysis and optimization of launch pad structure for launch vehicle which starts from a ship are purposes of this article. In this article a Finite Elements code was written in MATLAB software that is used for calculation of stresses and nodal displacements. The loads which missile, ship and wind apply to the launch pad structure for launch vehicle have been considered. Simulated Annealing (SA) algorithm was used for optimization of design. So a SA code was written in MATLAB. This code uses the Finite Elements method for calculation of stresses and the displacements. In this article, the objective function is set to minimize the weight of the structure. The constraints imposed to the analysis are the allowable stress and the displacement which are respectively 153.3 Mpa and 3 mm. The design variables are Specification of cross sections which are thickness and external diameter. By calculating the applied loads to the structure and appropriate modeling, stresses and nodal displacements were obtained as results of Finite Elements code and by using Simulated Annealing algorithm, cross sectional areas were obtained.
Aerospace Knowledge and Technology Journal
Malek ashtar University of Technology
2322-1070
7
v.
1
no.
2018
129
142
http://www.astjournal.ir/article_31791_d41d8cd98f00b204e9800998ecf8427e.pdf