https://jast.hho.msu.edu.tr/index.php/JAST/issue/feed Journal of Aeronautics and Space Technologies 2024-01-30T00:00:00+03:00 Journal of Aeronautics and Space Technologies jast@hho.msu.edu.tr Open Journal Systems <p><iframe src="https://jast.hho.msu.edu.tr/iFrames/summary.html" width="100%" height="180" frameborder="0" marginwidth="0" marginheight="0" scrolling="no"></iframe></p> https://jast.hho.msu.edu.tr/index.php/JAST/article/view/552 A Review on Post – Buckling Behaviors of Composites: Crippling Phenomenon 2023-10-13T10:49:58+03:00 Emine Gülşah Yıldırım egulsahyildirim@gmail.com Rahmi Ünal runal@gazi.edu.tr <p>Buckling phenomenon is a common failure mode for composite materials under the effect of compressive loading which is mainly investigated in two stages as pre – buckling and post – buckling. At the pre – buckling phase, the deformations take place temporarily in elastic range. However, load carrying capacity of a member can be increased by regarding the post – buckling process. Therefore, it is important to determine the final and maximum load carrying ability of the structure. Since, at the end of the post – buckling, the body cannot carry load and crippling failure takes place. In this review article, crippling behavior of the composite structures is investigated. After describing the crippling phenomenon, this study mainly investigates both experimental and theoretical points of views. In this scope, affecting parameters such as stacking sequence, geometrical properties and boundary conditions are determined. Then, the improved theoretical approaches are stated. The compatibilities of the test results are assessed with theoretical studies.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies https://jast.hho.msu.edu.tr/index.php/JAST/article/view/555 Aeroacoustic Evaluation of a Simplified Weapon Bay under Transonic Conditions with Doors Oriented at Various Locations 2023-11-07T10:33:29+03:00 Ali Can Fadil alicanfadil@gmail.com Baha Zafer zaferba@itu.edu.tr <p>In this paper, a simplified transonic weapon bay with a L/D=5 and Mach number 0.85 was considered using the large-eddy simulation (LES) with dynamic kinetic energy subgrid-scale (SGS) model. The M219 geometry has been analyzed using OpenFOAM for three different configurations based on the position of the covers. The obtained results have been validated against reference studies and presented in terms of mean streamwise velocity profile, overall sound pressure level, sound pressure level and band-integrated sound pressure level in both spatial and frequency domains. In order to mitigate the high computational cost associated with acoustic analysis, a Cartesian mesh topology has been employed as an alternative approach. The numerical findings have demonstrated a comparable level of accuracy to simulations conducted with high-cell count meshes. Based on these findings, a cavity analysis has been conducted for the configuration with covers positioned at a position of 45°.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies https://jast.hho.msu.edu.tr/index.php/JAST/article/view/559 Entropy-based Constant and Variable Weight Determination for Decision Makers in Multi-Criteria Group Decision Making 2023-11-07T13:43:05+03:00 Tuncay Gürbüz tuncaygurbuz09@gmail.com Sevra Çiçekli sevracicekli@gmail.com <p>Properly assigning weights to decision makers in a group decision making environment is one of the essential processes of utmost importance as it can have a direct effect on the final outcome. This paper, basing on the entropy method, proposes a correct and efficient way to objectively assign weights to decision makers in a multi-criteria group decision making environment. Two approaches namely, constant and variable weighting, have been put forward whilst providing necessary proofs and numerical examples in order to show one of the existing ways in literature is erroneous as it is not resulting in weights that reflects entropy method’s basic intuition.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies https://jast.hho.msu.edu.tr/index.php/JAST/article/view/578 Free and Random Forced Vibration Analysis of Spherical Sandwich Shells 2024-01-04T10:17:52+03:00 Ufuk Kol kol.ufuk@gmail.com Vedat Ziya Doğan doganve@itu.edu.tr <p>This paper presents a detailed analysis of the free and random vibrations of an all-side-clamped spherical sandwich shell. The sandwich is composed of graphite-epoxy layers, each consisting of four laminas with different fiber orientations and an isotropic Kevlar 29 core layer. The study employs the First-Order Shear Deformation Theory (FSDT) to establish kinematic relations and Hamilton’s principle to derive the equations of motion. The sandwich shell is discretized, and equations of motion are reduced to algebraic equations using the Differential Quadrature Method (DQM). Natural frequencies are found and subsequently, the Generalized Alpha Method is applied to solve the random forced vibration problem. To validate the accuracy of the results, a comparison is made with solutions obtained using the ABAQUS software.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies https://jast.hho.msu.edu.tr/index.php/JAST/article/view/576 Control of a Thermoelectric Cooling Module by Metaheuristic Optimization Algorithms 2024-01-04T08:58:25+03:00 Tufan Koç jast@hho.msu.edu.tr Nevra Bayhan nevra@iuc.edu.tr <p>In this study, the proportional-integral-derivative (PID) controller of a sample thermoelectric cooler (TEC) system model is optimized using four different metaheuristic optimization algorithms. For this aim, the classical PID and the metaheuristic optimization algorithms as Coronavirus Herd Immunity Optimization (CHIO), Atomic Search Optimization (ASO), Artificial Bee Colony (ABC) and Particle Swarm Optimization (PSO) were used for control of a TEC system. The settling time and maximum overshoot criteria are used to compare performances of the optimized controllers. -20°C is the desired temperature for the cold side of this thermoelectric module. Since TEC systems require quick cooling, CHIO-PID performs the best because it is the first to reach the set temperature of -20 ˚C in 42 seconds at the 1% band limit.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies https://jast.hho.msu.edu.tr/index.php/JAST/article/view/560 Effects of Climate Change on Takeoff Distance and Climb Rate; A Case Study: Boeing 737-800 Max Airplane 2024-01-04T08:59:42+03:00 Şeyda Yakçınkaya Çağlıyan yalcinkaya21@itu.edu.tr Deniz Demirhan demirhand@itu.edu.tr <p>The inevitable increase in average air temperature due to global warming undoubtedly affects the aviation sector as well. The increase in maximum and average air temperatures has a significant effect on the weight and fuel intake for takeoff performance, especially at airports with high altitudes and short runways. Air density is a critical factor in lift generation, and it can impact the aircraft's performance, especially during takeoff in warmer conditions. An augmentation in air temperature and pressure altitude is expected to decrease the takeoff performance. In this study, the impacts of climate change on the takeoff distance and climb rate for 10 airports in Türkiye are examined. This article examines the takeoff distance and climb rates in different periods during the summer months: past period from 1980 to 2010, the close future from 2023 to 2053, and the distant future from 2069 to 2099. The analysis reveals that as the air temperature increases, the takeoff distance increases by 4-7% and the climb rates decrease by 3-5% between close and distant future in summer.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies https://jast.hho.msu.edu.tr/index.php/JAST/article/view/579 Thermal Structural Design Aspects of Military Aircraft 2024-01-12T08:52:11+03:00 Mustafa Tolga Yavuz yavuzmusta@itu.edu.tr Ibrahim Ozkol ozkol@itu.edu.tr <p>This study presents the thermal-structural design aspects of military aircraft, exploring key components such as the evolution of fighters, high-temperature effects, airframe construction, and the role of thermal structural tests. From the early days of flight to the present day, the pursuit of supersonic flight has reshaped aviation, defining new thresholds for speed, agility, and combat capability. As known, high-temperature effects in airframes have been a substantial focus, with researchers and engineers grappling with challenges such as material degradation and thermal fatigue cracks resulting from elevated temperatures. The study emphasizes the pivotal role of materials capable of withstanding demanding extreme thermal environments, essential for ensuring the structural integrity and functionality of advanced aerial vehicles. Airframe construction of aircraft stands at the intersection of combat demands and cutting-edge technology, requiring innovative design solutions to address thermal stresses arising from sudden temperature changes. Furthermore, the study highlights the significance of thermal structural tests in validating designs and ensuring the safety, reliability, and performance of aircraft. Through an exploration of these crucial aspects, the study contributes to the broader understanding of the complex interplay between design, materials, construction, and testing in the thermal-structural design of military aircraft.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies https://jast.hho.msu.edu.tr/index.php/JAST/article/view/557 Fault Tolerant Controller Design for the Quadrotor with Variable Actuator Levels 2024-01-22T08:28:14+03:00 Ahmet Ermeydan aermeydan@eskisehir.edu.tr <p>In this study, proportional controller design is performed for different scenarios using a nonlinear quadrotor model. The state-space model of the quadrotor, whose flight principles are explained, and equations of motion are summarized, is obtained using a Taylor series expansion. Using the model, controller coefficients are designed for both fault-free and faulty conditions and compared. Using the controller gains designed for the fault-free condition, simulations are conducted both in a healthy state and, for comparison purpose, in a faulty state. The comparison reveals that the coefficients designed for the faulty condition exhibited much more robust behavior than those designed for the fault-free condition.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies https://jast.hho.msu.edu.tr/index.php/JAST/article/view/556 Robust Flight Control for Unmanned Aerial Vehicles: The Fusion of Full State Feedback and Extremum-Seeking Control 2023-11-24T09:51:54+03:00 Haci Baran baranh16@itu.edu.tr Ismail Bayezit bayezit@itu.edu.tr Ahmad Irham Jambak irhamjambak21@itu.edu.tr <p>The objective of this research is to develop an advanced flight controller that can effectively manage aircraft systems, maintain control, and effectively reject external disturbances and faults. To achieve this goal, the controller is designed using K-control gains in combination with the extremum-seeking control algorithm. The K-gains, crucial for ensuring stability and control of the fixed-wing unmanned aerial vehicle, are determined using the Full State Feedback (FSF) technique. However, FSF, does not have the capabilities to mitigate significant external threats. To mitigate these risks, the Extremum Seeking Control (ESC) method is incorporated into the controller. This adaptive approach enables the system to adapt and adjust parameters in the presence of unknown inputs, ensuring the system's response remains under control. In addition to the ESC-based controller, a Linear Quadratic Gaussian (LQG) regulator is also designed, and our work is compared with it to show the superiority of the proposed method.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies https://jast.hho.msu.edu.tr/index.php/JAST/article/view/580 Affordable and Accurate Numerical Predictions of Helicopter Rotor Noise in Forward Flight 2024-01-02T07:30:01+03:00 Tugrul Teoman Ozturk ttozturk@itu.edu.tr Alim Rüstem Aslan jast@hho.msu.edu.tr <p>In the present work, a numerical methodology is<br />developed for affordable and accurate analysis of<br />helicopter rotor noise in forward flight. The flow<br />field is obtained using unsteady compressible<br />flow analyses using commercially available<br />computational fluid dynamics (CFD) solver<br />FLUENT. Azimuthal variations of the flap and<br />pitch motions of the blades are prescribed a<br />priori as high order polynomial equations<br />through a user-defined function. The rotor noise<br />is predicted using Fluent Acoustic module based<br />on the Ffowcs-Williams and Hawking's equations.<br />Methodology is verified using HART II<br />experimental setup and data which includes<br />flapping, pitching, lead-lag motion and elastic<br />torsion for each rotor blade. Individually defined<br />blade motion is found critical for an accurate<br />acoustic prediction based on the obtained CFD<br />calculation. The present predictions compare<br />very well and performs better than other<br />previous CFD analysis both for minimum noise<br />and baseline case at maximum sound pressure<br />level (SPL) of HART II data, even with meshes of<br />7-8 million cells rather than tens of millions<br />usually needed.</p> 2024-01-29T00:00:00+03:00 Copyright (c) 2024 Journal of Aeronautics and Space Technologies