Journal of Aeronautics and Space Technologies <p>As National Defense University Hezârfen Aeronautics and Space Technologies Institute,&nbsp;our vision is to educate innovative academic personnel with an enterprising spirited professionalism. Aiming to give superior qualifications for both national and international standards, we are striving for our academic potential to contribute scientific and technologic developments parallel to social demands and becoming a pioneer on their respective fields of studies.</p> <p>The Journal of Aeronautics and Space Technologies is published as an international refereed journal that consists of scientific and academic knowledge in January and July biannually by Hezârfen Aeronautics and Space Technologies Institute.</p> <p>The Journal of Aeronautics and Space Technologies is publishing the article without charging any fee from the author (Free of charge) and offering their readers to read/download articles freely (Open-access) without any type of fee.</p> National Defense University Hezârfen Aeronautics and Space Technologies Institute en-US Journal of Aeronautics and Space Technologies 1304-0448 <p>The manuscript with title and authors is being submitted for publication in Journal of Aeronautics and Space Technologies. This article or a major portion of it was not published, not accepted and not submitted for publication elsewhere. If accepted for publication, I hereby grant the unlimited and all copyright privileges to Journal of Aeronautics and Space Technologies.<br><br>I declare that I am the responsible writer on behalf of all authors.&nbsp;</p> <p>&nbsp;</p> Dual-band Frequency Selective Surface Design for GSM Shielding Applications <p>Global Mobile Communications (GSMs) systems have developed very rapidly over the past decades. Mobile phone base stations are located almost everywhere nowadays. However, there is a deep concern about the health associated risks of electromagnetic radiation of GSM signals. Unwanted interference between GSM systems and electronic devices is another important issue to be considered. Transforming building surfaces to frequency selective filters is an efficient solution approach to decrease RF exposure levels inside the buildings and to prevent unwanted interference. As a solution approach, single-layer frequency selective surface (FSS) geometry is proposed in this work, which reflects 900 MHz, 1800 MHz and 2100 MHz GSM frequency bands. 1800 MHz and 2100 MHz GSM bands are considered as a single frequency band in this work since they are very close to each other. Ansoft HFSS software is used for simulation, design, and optimization purposes. The equivalent circuit model is also utilized at the design and optimization stages. Achieved results show that proposed FSS element geometry has a stable frequency response up to 60 degrees of incidence angle with minimum of 10 dB attenuation.</p> Bora Döken İhsan Güney Koç Ali Berkay Koç Mikail Altan ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 1 7 Investigation of Flow Field Around a Naca Airfoil With OpenFoam and Fluent CFD Software <p>In the last years, Fluent and OpenFoam are the two most reliable CFD software used in simulations of different flow fields in both academic and industry. In this study, the performance of these two CFD simulation software relative to each other was determined for the same boundary conditions for a selected flow area. The highlight of OpenFoam CFD software is that it is free software with open source. In this context, our primary goal is to lead the spread of open-source and free software in the implementation of engineering processes in our country. As the flow area, an airfoil with Naca 2415 section manufactured by Harran-Ravens team was selected for Teknofest competition. As a result of the simulations carried out, the aerodynamic forces and moments that affect the airfoil have been determined. In terms of lift force, the deviation between the two simulations is 6%, while in the drag force the said deviation increases up to 15.5%. Also, the lift and drag coefficient calculated by both simulation results are in good agreement with Airfoil Tools database</p> Zeynel Abbidin Firatoglu Yusuf İlhan Hakki Keskin Yusuf ISIKER ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 9 18 Prediction of Fuel Tankering in Aviation Industry with Machine Learning Algorithms <p>Fuel tankering is a method that is used in the aviation industry to reduce fuel expenses caused by fuel price differences between departure and arrival airport. It provides profitable transport of required fuel for the next flight. Today, there are some basic customizable formulas/models used in the fuel tankering calculation in the literature; however, the customizability of the formulas/models reveals different parameter preferences (such as weather, route, etc.) for the researchers making calculations, and accordingly, the results to be obtained for fuel tankering may vary. Also, an explanatory study in which artificial intelligence, which is used in various fields such as flight planning, diagnose aviation turbulence, is used in fuel tankering estimation/prediction, could not be found in the literature. For these reasons, in this study, it is aimed to predict fuel tankering in the airline industry with machine learning algorithms that learn from raw data independently of these formulas/models. The dataset is obtained from a commercial airline company in Turkey. In this scope, k-Nearest Neighbors Algorithm, C4.5 Decision Tree Algorithm, Naive Bayes Classifier, and Artificial Neural Networks (ANNs) are used to generate prediction models. According to the results of the study, the best performance is obtained with ANNs by using the Backpropagation algorithm (accuracy = 0.838). Furthermore, an online application for predicting fuel tankering is developed with the ANN model. The machine learning model suggested and the online application developed in this study are one of the most important examples of the integration of artificial intelligence to the airline industry in terms of resource allocation and profitable transport. Also, this study will provide a different insight alternatively to the fuel tankering calculations that are used by aviation companies.</p> İlker Güven Yılmaz Elif Kartal Zeki Özen Sevinç Gülseçen ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 19 34 An Open-Source Hypersonic Solver for Non-equilibrium Flows <p>An implementation of a thermally non-equilibrium modeling on an existing open-source CFD solver is presented in this study. A newly coded open-source Navier-Stokes solver, hyperReactingFoam, including two-temperature model was developed within the framework of OpenFOAM. Disregarding electronic states in ionizing flows, the solver decomposes equilibrium temperature into trans-rotational and vibrational temperatures in thermal non-equilibrium conditions. Relaxations between distinct energy pools are achieved by utilizing an additional vibrational energy equation for each specie in the mixture. Coupling between trans-rotational and vibrational energy modes is governed by Landau-Teller equation. For energy transfers between different vibrationally excited species, formulation that is proposed by Knab et al. is implemented into the solver. The chemistry-vibrational coupling is realized by the Park TTv Model. Due to the multi-component nature of reacting flow, mixture pressure is calculated by using Dalton's Law from partial pressures of each reacting specie. Code validation tests are conducted on frequently used benchmark models such as adiabatic heat bath, blunted cone, and double cone models. It has been shown that hyperReactingFoam solver is in good agreement with other numerical solvers and experiments available in the literature.</p> Davut Vatansever Bayram Celik ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 35 52 Coupling of Peridynamics and Timoshenko Beam Theory for the Stress Analysis of Laminated Composite Materials <p><em>This study investigates the bending behavior of laminated composite beams by using Peridynamic Least Squares Minimization (PDLSM) approach and T</em><em>imoshenko Beam Theory</em><em> (TBT). The PDLSM converts any arbitrary order derivatives of a function in their nonlocal forms with high accuracy. Therefore, it is highly suitable for the solution of TBT equilibrium equations. The influence of span-to-thickness ratios, loading and boundary conditions, as well as laminations on the stress and deformation fields of laminated composite beams, were investigated in detail. The accuracy and robustness of the present approach namely Also, the PDLSM was used for the transverse shear stress calculations from the stress equilibrium equations. It was demonstrated that the PD-TBT successfully predicted the deformation and stress fields in the laminated beams.</em></p> Mehmet Dorduncu ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 53 62 Solar Eclipse Effects on Clear Days: Case of 11 August 1999, Turkey <p>Turkey was one of the perfect sites to watch the total solar eclipse on August 11, 1999. The total eclipse was observed across a diagonal path extending from Bartın (41.63<sup>o</sup>N, 32.33<sup>o</sup>E) on the Black Sea coast to Diyarbakır (37.55<sup>o</sup>N, 40.14<sup>o</sup>E) in southeastern Turkey. The weather was cloudless. Therefore, the eclipse effects were expected to be clearly observable. The cooling effect of total eclipses is observable in temperature and humidity records. It was suggested that the total eclipse can produce a local cyclonic (anticlockwise) rotation of the surface winds within the totality region and the strength of the wind decreases. In this study, we investigate some of these eclipse related effects using surface temperature and wind measured at the meteorological stations located along the totality path of the August 11, 1999 eclipse. Analysis results show a maximum temperature drop of 4<sup>o</sup>C and wind speed decrease of 6 m/s at the maximum time of the eclipse. It was seen that both temperature and wind speed drops increase with the increasing sea level height.&nbsp; In two of the twelve selected &nbsp;stations, an anti-cyclonic rotation of the wind direction within the umbral region was detected.</p> Emine Ceren Kalafatoğlu Eyigüler Zerefşan Kaymaz ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 63 70 Automated Real Time Detection of Suspicious Appearances Using Deep Learning <p>Security camera systems especially in public areas such as airports, courthouses or sports facilities etc. are used to find fugitive persons or detect suspicious behaviors manually under the monitoring of an operator. In hallway-like sections in public facilities, repeated appearances of an unknown ordinary person in a short span of time can be defined as suspicious behavior. However, the fact that multiple cameras are monitored by a single operator makes it harder to detect suspicious behaviors especially in crowded fields. Therefore, support decision systems are required to support operator. If individuals are detected on images automatically and their appearances on the camera are recorded on a database by giving them a temporary identity, suspicious behaviors can be reported to an operator as a support decision system. For this reason, two different methods are used together as a hybrid solution in the study; a MTCNN based facial detection is used on the real time security camera images that currently provide face images, and an identification method, created with facial landmarks produced with a deep learning algorithm that was trained with res-net, was used on the obtained person’s face images. It has been presented that suspicious behaviors can be detected by interpreting the temporary identity information that was obtained. The success of the application was experimentally tested, and the causes of success and failures in the results were discussed.</p> Melek Tursun Ömer Çetin ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 71 78 Unscented Kalman Filter Based Attitude Estimation of a Quadrotor <p>Quadrotors are well - known unmanned aerial vehicle structures that have some advantages such as hovering, vertical take – off and landing, and low – speed flight. On the other hand, quadrotors are subjected to modeling and sensor uncertainties that lead to erroneous state estimation. Kalman filter has been proven to be the optimal estimator for the Gaussian distributed noise for linear processes. However, linear dynamical models of the quadrotors are not accurate representations of the systems due to nonlinearities, and coupling between the states. Extended Kalman filter (EKF) is proposed to solve the above issue. But, first order Taylor series approximation for the nonlinear state model may lead inefficiencies. For this reason, another Kalman filter framework is proposed that employs unscented transformation (UT). Unscented Kalman filter (UKF), can model the state distribution as Gaussian random variable to the third degree for arbitrary nonlinearities.</p> <p>So, in this study, unscented Kalman filter based estimation scheme is presented to overcome the sensor and model noises for nonlinear quadrotor attitude dynamics. According to the statistical analysis, the approach can estimate and reduce the mean absolute error, root mean square error and also variance of the noise for all attitude states.</p> Aziz Kaba ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 79 88 Ensuring Survivability of Spacecraft Attitude Control System at Failures in Flywheel Cluster <p>A method for ensuring the survivability of a spacecraft attitude control system with minimally redundant cluster of the flywheels and magnetic actuator at the faults of any reaction wheels are presented. The results of computer simulation were obtained and it was found if any two of the four flywheels according to the General Electric scheme fail, digital control of the flywheel cluster and magnetic drive allows the land-survey satellite to maintain the ability for observation of given terrestrial targets.</p> Sergey Somov Tatyana Somova ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 89 98 Investigation of Joining Methods of Honeycomb Composite Panels Used in Structural Elements of Aircraft Cabin Units <p>Design, material selection, production and assembly of structural elements used in aircraft are critical problems of the aeronautical industry. The usability of these elements is determined by considering parameters such as strength, cost, and weight. Accordingly, this study aims to optimize the joining methods of different thickness honeycomb composite panels used in the aviation industry, considering these parameters. Panel type, panel thickness and joining methods were determined as input parameters, and fracture force, displacement, cost, and weight as output parameters. Tenon-mortise, double-sided bracket, single-sided bracket, and extrusion methods were investigated for L and T-type panels. Panel thicknesses were determined as 10 mm and 22 mm according to standards, tensile test and finite element analysis were performed. The weight and cost of the panels were determined by the process analysis. The obtained findings were optimized according to multi-criteria decision making, and response surface analysis methods. In the analysis, tensile strength maximization, displacement, cost, and weight minimization were determined as target functions. At the end of the study, the optimum thickness value for both types of panels was determined as 22 mm, and the optimum joining method was tenon-mortise.</p> Sena Kabave Kılınçarslan Aslan Kahraman Erhal Şeyma Korkmaz Hüseyin Çetin ##submission.copyrightStatement## 2021-01-21 2021-01-21 14 1 99 117