Papers by Dilek Funda Kurtulus
55th AIAA Aerospace Sciences Meeting, 2017
This paper exploresthedesign and testing ofa flapping wing four-bar mechanism. A four-bar linkage... more This paper exploresthedesign and testing ofa flapping wing four-bar mechanism. A four-bar linkage system kinematic analysis is introduced for flapping wing motion. Four-bar mechanism is activated by a servo motor which is driven by microcontroller. The wing undergoes apure flapping motion at afixed pitchangle. Force measurements are performed for hover modeby using a force transducer. In addition, 3D numericalanalyses are performed and the results are compared with the experimental measurements. Overall, CFD results showgood agreement with the experimental data
Engineering Research Express
This study aims to create an interdisciplinary, multi-level design approach for fixed wing aircra... more This study aims to create an interdisciplinary, multi-level design approach for fixed wing aircrafts. A case study is performed using Cessna 172N aircraft characteristics that is based on a mathematical model having six degrees of freedom (DOF). A Model Based Aircraft Design Software (MAD) is developed using a mathematical dynamic model in Python environment for use in the optimization phase of the Cessna 172N aircraft. The MAD environment is composed of analysis tools that communicate with each other by an automated process chain system. The model includes aerodynamics, engine, mass, control, atmosphere, and landing gear submodules. In addition, the model has trim and 6 DOF simulation analysis capabilities which provide a diversity of analyses that can be considered in early design phases. In order to get trimming and simulation capability, MAD software does not need any precalculated aerodynamic database. The force and moment calculations are performed instantly via DATCOM and AVL...
International Journal of Sustainable Aviation, 2020
Aerodynamics and structural dynamics of the insect wings are widely considered in flapping wing m... more Aerodynamics and structural dynamics of the insect wings are widely considered in flapping wing micro air vehicle (FWMAV) applications. In this paper, the aerodynamic characteristics of the three-dimensional flapping wing models mimicked from the bumblebee and hawkmoth wings are numerically investigated under steady flow conditions. This study aims to simulate the one-way fluid-structure interaction (FSI) of these bio-inspired wings by transferring the aerodynamic load obtained from the computational fluid dynamics (CFD) into the finite element method (FEM) solver as a pressure load. The static aeroelastic responses of the wings under the pressure load are compared for different materials, namely, cuticle, aluminium alloy, and titanium alloy at various angles of attack (α = 0°-90°). CFD analysis shows that the hawkmoth wing model at α = 5° has the highest lift-to-drag ratio (L/D). FSI analysis demonstrates that the cuticle hawkmoth wing model at α = 90° undergoes the highest tip deflection.
Serpentine inlets (S-ducts) are used to supply air to the engine when it is buried in the aircraf... more Serpentine inlets (S-ducts) are used to supply air to the engine when it is buried in the aircraft. An intake is expected to transport the air mass flow required by the engine with minimum total pressure losses to the aerodynamic interface plane. Separation occurs inside the S-duct and generates distortion leading to instabilities. The flow structure in a diffusing S-duct is numerically investigated. Mesh dependency and different turbulence models are studied. Furthermore, it is surveyed that how the inlet profile influences the upstream flow structure. Results reveal the streamwise flow separation within the duct. Secondary flows due to spatial pressure gradient are detected. Total pressure loss is observed due to the flow structure and total pressure distortion at the AIP is calculated. Numerical results coincide well with the experimental results. Reynolds stress model is found to give the best solutions among other turbulence models.
Sürdürülebilir Havacılık Araştırmaları Dergisi, Dec 11, 2017
Son yıllarda çırpan kanatlı mikro insansız hava araçları aerodinamiği üzerine çokça incelemeler y... more Son yıllarda çırpan kanatlı mikro insansız hava araçları aerodinamiği üzerine çokça incelemeler yapılmaktadır. Kuşlar, böcekler gibi doğal uçan hayvanların uçuş mekanizmaları analiz edilerek insan yapımı robotik insansız hava araçları üretilmektedir. Genel olarak düşük Reynolds sayısındaki akışların incelendiği çalışmalar hem biyolojik uçan hayvanları hem de insan yapımı Mikro Hava Araçları (MHA) kapsamaktadır. Bu çalışmada kanatlı böceklerin uçuşları ve özellikleri mikro hava araçları tasarımına ilham teşkil etmeleri adına özetlenmiştir. Çalışmada ayrıca deneysel çalışmalarda kullanılabilecek boyut analizi gösterilmiştir.
TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2021
The aerodynamic design and analysis of an Unmanned Air Vehicle, capable of vertical takeoff and l... more The aerodynamic design and analysis of an Unmanned Air Vehicle, capable of vertical takeoff and landing by employing fixed four rotors on the tilt-wing and two rotors on the tilt-tail, will be presented in this study. Both main wing and the horizontal tail can be tilted 90°. During VTOL, transition and forward flight, aerodynamic and thrust forces have been employed. Different flight conditions, including the effects of angle of attack, side slip, wing tilt angle and control surfaces deflection angle changes, have been studied with CFD analysis. For a Tilt-Wing UAV, there are challenges like high non-linearity, vulnerability to disturbances during hover and transition, cross-coupling between three axes, very low time to double amplitude of the open-loop system. Therefore, the aerodynamic analysis has been done in detail considering especially the challenges in transition phase of the flight envelope.
European Archives of Oto-Rhino-Laryngology, 2016
Glottic obstruction is a major cause of dyspnea. Without understanding the normal function of the... more Glottic obstruction is a major cause of dyspnea. Without understanding the normal function of the glottis in breathing, treating dyspnea does not restore normal physiology. Therefore, we designed a computational fluid dynamics (CFD) model that tested the respiratory cycle in larynges with normal glottis and congenital glottic web (CGW). A CGW case and a control subject (CC) were selected from the computed tomography (CT) archive. 3D computational models of the larynges with structured boundary layer were constructed from axial CT images after mesh refinement study. CFD analyses were based on the Reynolds-averaged Navier-Stokes approach. Incompressible flow solver (pressure-based) and SST k-w turbulence model were chosen for this study. To simulate a real-time breathing process, time varying flow rate boundary condition was derived from the spirometer of a healthy, non-smoking woman. Glottic areas were measured as 51.64 and 125.43 mm(2) for the CGW patient and CC, respectively. Time-dependent velocity contours and streamlines for the CC and CGW patient were drawn. The CC showed uniform flow, all through the inspiration and expiration phases. However, the CGW patient showed separation of flow at the glottis level, which caused areas of stagnation in the supraglottis (during expiration) and the subglottis and trachea (during inspiration). Specialized geometry of the normal larynx maintained uniform flow with low shear stress values on the wall even at high mass flow rates. Distortion of this geometry may cause obstruction of flow at multiple levels and, therefore, should be evaluated at multiple levels.
First Issue of 2019
In this study, 3D model of the bio-inspired blow fly wing Callphere Erytrocephala is created and ... more In this study, 3D model of the bio-inspired blow fly wing Callphere Erytrocephala is created and aeroelastic analysis is performed to calculate its aerodynamical characateristic by use of numerical methods. In order to perform the flapping motion, a sinusoidal input function is created. The scope of this study is to perform aeroelastic analysis by syncronizing computational fluid dynamics (CFD) and structural dynamic analysis model and to investigate the unsteady lift formation on the aeroelastic flapping wing. Keywords: Micro air vehicle, Fluid-structure interaction analysis, Computational Fluid Dynamics, Structural dynamic analysis, Finite element analysis
Sustainable Aviation, 2019
Since the beginning of the aviation industry, fossil fuel is being used as the only source of fue... more Since the beginning of the aviation industry, fossil fuel is being used as the only source of fuel to power airplanes. Each year the popularity of aviation industry among the passengers is increasing dramatically because of its short journey time. Therefore, the demand of fossil fuel is also increasing to support the additional need. However, the stock of fossil fuel is reducing and will all be consumed within a couple of decades. In addition to this, the increment of greenhouse gas has become another issue, which should be dealt with urgently in order to not contribute to global warming. Because of these upcoming problems, another source of fuel and a significant development in aircraft design are a must for the future of aviation industry. Some new sources of fuels are being tested as alternative fuels. Solar power, biofuels, and hydrogen fuel are some of them. New techniques for aircraft design have also been developed within the last couple of years. To make these new ideas avai...
The study presents the newly developed fast three-dimensional grain burnback tool. The computatio... more The study presents the newly developed fast three-dimensional grain burnback tool. The computational method that has been developed is based on minimum distance calculation technique. Structured grid for computational domain modeling has been used, and grid based-surface propagation method has been utilized for grain burnback simulation by using STL and SLP file formats. The developed simulation tool is able to solve very complex grain geometries. The auto mesh interface tool has been tested for quite complex grain geometries. The solution domain has been created properly without any user interference. It is observed that the determined specific distance ratio gives an acceptable accuracy within a short computation time. The burnback simulations of a real solid rocket motor indicate that the symmetrical model used with the initial distance calculation method provides an important computational time improvements. The burnback analysis of symmetrical models, initial distance calculati...
The performance of the modern aeroengines is highly dependent on the turbine inlet gas temperatur... more The performance of the modern aeroengines is highly dependent on the turbine inlet gas temperature. However, the turbine inlet temperatures of the today’s engines are already beyond the material structural limits. Hence, the turbine section must be cooled down to acceptable levels. Various types of cooling methods like internal cooling, film cooling, impingement cooling, etc. are typically applied to the gas turbine blades. Current research focuses on experimentally and numerically investigating the thermal performance of a two-pass channel. A rectangular cross-section tunnel with two passages and a U-turn section that mimic the modern gas turbine cooling configurations was investigated. The ribs with square cross section are located on the bottom wall of both passages. The ambient air is sucked to the wind tunnel by using a blower. The bottom wall of the test section was heated by a foil heater which generates uniform heat flux. The experiments were conducted at Reynolds number of ...
The aerodynamic phenomena of the flapping motion in hover mode is widely considered in micro air ... more The aerodynamic phenomena of the flapping motion in hover mode is widely considered in micro air vehicle (MAV) applications. In this study, the aerodynamics of a three-dimensional rigid wing mimicked from the hawkmoth Manduca sexta is numerically investigated under pure plunge motion. The sinusoidal motion is provided with a user-defined function (UDF) to flap the wing, and the computational fluid dynamics (CFD) is used for the numerical analysis. This paper presents the effects of various parameters such as wingbeat frequency (f), stroke plane angle (β) and stroke amplitude (Φ) on the wing aerodynamics during hovering flight. INTRODUCTION In recent years, the aerodynamic phenomena is widely studied on the low-Reynolds-number regimes to build micro air vehicles (MAVs) with the small sizes (<15 cm of wingspan) and low masses (<100 gr) by inspiring from the flying animals [Kurtulus, 2018]. There are three kinds of MAVs namely fixed wing, rotary wing and flapping wing. In compari...
International Journal of Micro Air Vehicles, 2019
The present paper aims to investigate numerically small amplitude oscillation of NACA 0012 airfoi... more The present paper aims to investigate numerically small amplitude oscillation of NACA 0012 airfoil at Re ¼ 1000. The airfoil is sinusoidally pitching around the quarter chord point with 1 pitch amplitude about a mean angle of attack. The computations are performed for mean angles of attack ranging from 0 to 60 and for pitching frequencies of 1 Hz and 4 Hz. The effect of the mean angle of attack and pitching frequency on the instantaneous forces as well as the vortex structure is investigated in comparison with the non-oscillatory conditions. It was shown that airfoil oscillations at the investigated conditions change the amplitude of oscillation of the aerodynamic loads. The instantaneous drag coefficient is always positive for pitching airfoil at 1 Hz. In the meantime, there are time intervals where instantaneous drag coefficient becomes negative for pitching motion at 4 Hz for mean angles of attack from 3 to 36 .
Sürdürülebilir Havacılık Araştırmaları Dergisi, 2016
Bu çalışma, hibrit insansız hava aracının (HİHA) tasarımı, matematiksel olarak modellenmesi, dene... more Bu çalışma, hibrit insansız hava aracının (HİHA) tasarımı, matematiksel olarak modellenmesi, denetimci tasarımını ve döngüde donanım testlerinden oluşmaktadır. Sabit kanatlı hava aracı olarak uzaktan kumandalı E-Flite Apprentice marka model uçak seçilmiş ve şaside yapılan değişikler ile dikey iniş kalkış özelliği kazandırılmıştır. Bu tarz hibrit bir sistem, döner kanatlı sistemlerde olduğu gibi herhangi bir piste ihtiyaç duymadan dikey olarak iniş kalkış yapabilmekte ve sabit kanatlı sistemler gibi sabit kanat uçuş gerçekleştirebilmektedir. Bu hibrit sistemi matematiksel olarak modelleyebilmek için HİHA'nın sabit ve hareketli bileşenlerine yönelik sistem tanılama işlemlerinin yapılması gerekmektedir. Hava aracında dikey kaldırma ve yatay itki kuvvetlerinin üretimi için fırçasız motorlar; kanatçık, yatay dümen ve dikey dümen gibi kontrol yüzeylerinin denetimi için ise servo motorlar kullanılmaktadır. Fırçasız motorlara yönelik sistem tanılama çalışmaları için bir itki ölçüm sistemi, servo motorların sistem tanılama çalışmaları için ise bir açı ölçüm sistemi kullanılmaktadır. HİHA'nın kütle eylemsizlik momentleri ise çift telli sarkaç deneyi yapılarak bulunmaktadır. HİHA, Matlab/Simulink ortamında, deneysel olarak hesaplanan, sisteme özgü parametreler kullanılarak modellenmektedir. HİHA, dikey kalkış-iniş, sabit kanat-döner kanat uçuşu arasında geçiş ve sabit kanat uçuşu olmak üzere üç ana uçuş moduna sahiptir. HİHA otopilot algoritması olarak oransal-integral-türevsel (PID) ve doğrusal aktif bozucu sönümleme (LADRC) tip denetimci algoritmaları geliştirilip, performansları kıyaslanacaktır.
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Papers by Dilek Funda Kurtulus