Havada asılı konumdaki çırpan kanat profilinin sayısal ve deneysel analizi. Mikro hava araçları'na uygulaması

The aerodynamics phenomena of flapping motion in hover are considered in view of the future Micro Air Vehicle applications. The aim of this work is to characterize the vortex dynamics generated by the wing in motion using direct numerical simulation and experimental analysis then to propose a simplified analytical model for prediction of the forces in order to optimize the parameters of the motion leading to maximum force. A great number of cases are investigated corresponding to different angles of attack, location of start of change of incidence, location of start of change of velocity, axis of rotation, and Re number. The airfoil used is symmetrical. The flow is assumed to be incompressible and laminar with the Reynolds numbers between 500 and 2000. The experimental results obtained by the laser sheet visualization and the Particle Image Velocimetry (PIV) techniques are used in parallel with the direct numerical simulation results for the phenomenological analysis of the flow. The model developed for the aerodynamic forces is an indicial method based on the use of the Duhamel Integral and the results obtained by this model are compared with the ones of the numerical simulations.Ph.D. - Doctoral Progra

On the wake pattern of symmetric airfoils for different incidence angles at Re=1000

In the current study, numerical simulations are performed in order to investigate effects of incidence angle and airfoil thickness on alternating vortex pattern of symmetric airfoils at Re = 1000. This alternating vortex pattern is found to be significantly varying in shape as the incidence angle increases. The results are obtained with 1 degrees increment from 0 degrees to 41 degrees and then with 10 degrees increment from 40 degrees until 180 degrees. The instantaneous and mean vortex patterns are investigated around 2% thick (NACA 0002) and 12% thick (NACA 0012) airfoils. The mean lift, drag, and pitching moment coefficients in addition to Strouhal number are computed and compared with the results available in literature. It is found that the wake behind the airfoil exhibits a continuous vortex shedding pattern below 8 degrees incidence angle for NACA 0002 and below 7 degrees incidence angle for NACA 0012 at Re = 1000. The wake structures are classified into five different modes according to their pattern obtained from instantaneous and mean vorticity fields by also taking into account the amplitude spectrum of the lift coefficient, the instantaneous and mean aerodynamic force coefficients, velocity fields, and the longitudinal and lateral vortex spacings

On the Unsteady Behavior of the Flow Around NACA 0012 Airfoil with Steady External Conditions at Re=1000

Even for the stationary airfoils, due to the boundary and shear layer interactions of upper and lower surface of the airfoils, alternating vortex patterns form and the flow becomes time dependent. In the current study, the unsteady behavior of the flow around a symmetric airfoil is considered as incidence angle increases. The flow patterns are presented for wide range of angles of attack values. The vortex pattern generated is analyzed numerically for different angles of attack at Re=1000 around NACA 0012 airfoil. At this Reynolds number, the flow is laminar and boundary layers are quite thick. Flow separation and unsteady vortex shedding is observed even at low angles of attack. For NACA 0012 airfoil, the unsteady vortex pattern is observed at about 8 degrees angle of attack for Re=1000. Spectral analysis is performed for angles of attack ranging from 0 degrees to 90 degrees. It is presented that amplitude spectrum of lift coefficient (C-l) start to shows a peak at 8 degrees for NACA 0012 and the aerodynamic forces presents oscillatory behavior afterwards. The effect of angle of attack to wake pattern and instantaneous and mean aerodynamic coefficients are discussed. The time-averaged streamlines, pressure and skin friction coefficients are analyzed to observe the vortex formation and separation from the airfoil upper surface at this low Reynolds number

Vortex flow aerodynamics behind a symmetric airfoil at low angles of attack and Reynolds numbers

The low Reynolds number aerodynamics is important to investigate for micro air vehicle applications. The current paper covers numerical simulations to present the downstream development of the wake patterns and detailed analysis of the vortices generated at the downstream of NACA 0012 airfoil around the critical angle of attack where the instantaneous vortex patterns are oscillatory and differ from the mean vortex pattern for low Reynolds numbers ranging from 1000 to 4000. The instantaneous and mean aerodynamic forces, pressure and skin friction coefficients, and vorticity values are compared in addition to the path of the vortex centers, their longitudinal and lateral spacings, Karman spacing ratios, and distortion ratios at the wake of the airfoil in regard to the different Reynolds numbers investigated. The streamwise and crosswise velocities of the vortex cores and relative velocities at different transverse locations are also discussed and presented in detail. The correlations between different non-dimensional numbers (St, Re, Ro) are obtained at these low Reynolds numbers investigated

Ability to forecast unsteady aerodynamic forces of flapping airfoils by artificial neural network

The ability of artificial neural networks (ANN) to model the unsteady aerodynamic force coefficients of flapping motion kinematics has been studied. A neural networks model was developed based on multi-layer perception (MLP) networks and the Levenberg-Marquardt optimization algorithm. The flapping kinematics data were divided into two groups for the training and the prediction test of the ANN model. The training phase led to a very satisfactory calibration of the ANN model. The attempt to predict aerodynamic forces both the lift coefficient and drag coefficient showed that the ANN model is able to simulate the unsteady flapping motion kinematics and its corresponding aerodynamic forces. The shape of the simulated force coefficients was found to be similar to that of the numerical results. These encouraging results make it possible to consider interesting and new prospects for the modelling of flapping motion systems, which are highly non-linear systems

Hava ve uzay hukukunda ticari hizmetlerden doğan hukuki sorumluluk

Son dönemlerde özel şirketler tarafından uzaya seyahatler düzenlenmeye başlanmıştır. Bu durum uzay turizmi ile uzay turisti, uzay katılımcısı veya uzay yolcusu gibi kavramların doğmasına sebep olmuştur. Bir uzay aracı ile seyahat eden uzay yolcusunun uğradığı zarardan doğan sorumluluğun tazmini konusu öğretide tartışmalıdır. Uzay cisminde bulunan uzay yolcusuna, yeryüzünde, hava sahasında veya uzayda başka bir fırlatan devletin uzay aracının çarpması halinde söz konusu zararı veren Fırlatan Devlet’in veya Uluslararası Örgütün uluslararası sorumluluğu doğacaktır. Oysa uzay cisminde bulunan uzay yolcusuna fırlatma esnasında, uzayda veya Dünya’ya dönüşü sırasında herhangi bir zararın gelmesi durumunda uzay yolcusunun içinde bulunduğu uzay cismini “Fırlatan Devletin” sorumluluğuna Sorumluluk Sözleşmesi’nin 7. maddesi gereği gidilemeyecektir. Sorumluluk Sözleşmesi Fırlatan Devletin vatandaşlarına ve fırlatma anından itibaren uzay cisminin inişine kadar uzay cismini çalışmasına katılan yabancı ülke vatandaşlarına uygulanmamaktadır. Bu durumda olan ve zarar gören uzay yolcuları ancak fırlatan devletin iç hukuk yollarına başvurarak zararlarını tazmin edebileceklerdir. Türkiye’de de Ulaştırma, Denizcilik ve Haberleşme Bakanlığı’nca hazırlanan “Türkiye Uzay Ajansı Kurulması ve Uzaya Yönelik Faaliyetlerin Düzenlenmesi Hakkında Kanun Tasarısı (Türkiye Uzay Kanunu Tasarısı)” Bakanlar Kurulu’nca 13.02.2017 tarihinde TBMM’ye sunulmuştur. Bu tasarı kanunlaşmamıştır. Bunun yerine, 13 Aralık 2018 tarihinde 30624 sayılı Resmi Gazete’de yayımlanan 23 nolu “Türkiye Uzay Ajansı Hakkında Cumhurbaşkanlığı Kararnamesi” ile Türkiye Uzay Ajansı kurulmuştur. Ne kararnamede ne de kanun tasarısında her ne kadar hüküm bulunmayan hallerde Türk Sivil Havacılık Kanunu (TSHK)’nun uygulanacağına dair bir hüküm bulunmasa da TSHK’nın sorumluluk hükümlerinin ulusal Uzay Hukuku’na uygulanmasından daha uygun bir yaklaşım yoktur. Ayrıca uzay araçları havalanabildikleri ve havada seyredebildikleri için atmosferde (hava sahasında) bulundukları sürece TSHK bakımından da hava aracı sayılmaktadır. Bu sebeple çalışmada iç hukukta uygulanması gereken kuralların düzenlenmesine ışık tutmak adına Hava Hukuku’nun ticari hizmet faaliyetleri ile ilgili hukuk kurallarına da başta TSHK olmak üzere değinilmiştir. In recent years, travels to space by private companies have started to be organized. This has led to the creation of concepts like space tourist, space participant or space traveler with space tourism. The rewards of responsibility for damage caused by a spacecraft to a space participant is a subject of discussion in the literature. The international liability of the Launching State or the International Intergovernmental Organization will result in the case of a damage given to a space participant in a space object of another launching state either on the surface of the earth, in air or in space. However, in the event of any damage to space passenger in the spacecraft during the launch of the spacecraft, in the space, or in the descent phase to the Earth, the space passenger shall not be subject to the 7th Article of the Liability Agreement for the responsibility of its own "Launching State". The Liability Convention does not apply to nationals of the launching State and to foreign nationals participating in space operations from the moment of launching to the descent of space object. In this case, the space passengers will only be able to compensate their damages by resorting to local remedies. In Turkey, Ministry of Transport, Maritime Communications prepared "Draft Law of Turkey Space Agency Establishment and Regulation of Space Activities (Turkey Space Law Draft)" which was submitted to parliament by Board of Ministers on 13.02.2017. This draft law has not been enacted. Instead, on 13 December 2018, Turkey Space Agency was established with "Turkey Space Agency on Presidential Decree" no. 23 published in the Official Gazette numbered 30624. In neither the decree nor the draft law, there is no provision that in cases where there are no provisions, the Turkish Civil Aviation Law (TSHK) should be applied, there will not be any more appropriate approach than applying TSHK's liability provisions to national Space Law. In addition, the space vehicles which could takeoff and cruise in the air, as much as they are in the atmosphere (airspace) they are counted as air vehicles by the provisions of THSK. For this reason, in order to clarify on the regulation of the rules that should be applied in domestic law, the provisions related to commercial service activities of Air Law are mentioned paying attention to provision in TSHK

Mha Tasarımlarına İlham Veren Kanatlı Böceklerin Uçuş Özellikleri

In the last years, there has been lots of investigation on the aerodynamics of flapping wing micro air vehicles. By analysing the flapping mechanics of natural flyers like birds and insects, human made robotical unmanned aircrafts are manufactured. In general, the works which investigates the flows at low Reynolds numbers covers both the biological flyers and human-made Micro Air Vehicles (MAV). In this work, the flight and properties of winged insects are summarized for the purpose of giving inspiration for the designs of Micro Air Vehicles. In addition, dimensional analysis which could be used for the experimental works is shown.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

Experimental Aerodynamics

Experimental techniques in aerodynamics: Pressure, temperature and velocity measurement techniques. Steady and unsteady pressure measurements and various types of pressure probes and transducers, errors in pressure measurements. Measurement of temperature using thermocouples, resistance thermometers, temperature sensitive paints and liquid crystals. Measurement of velocity using hot wire anemometry. Calibration of single and two wire probes. Velocity measurement using Laser Doppler Velocimetry and Particle Image Velocimetry. Data acquisition and digital signal processing techniques