Pilotuojamiems orlaiviams keliami vienodi skrydžio saugumo reikalavimai nepriklausomai nuo jų dydžio ir skrydžio greičio. Sparčiai vystantis mažų greičių aviacijai aktualu mažinti tokių orlaivių projektavimo, gamybos ir bandymų išlaidas, išlaikant tą patį skrydžio saugumo lygį. Kadangi orlaivio skrydžio savybes daugiausia nulemia sparno aerodinaminės savybės, ypač aktualu pigiai ir greitai kurti sparnus mažų greičių orlaiviui. Tam reikalingas patikimas, sąlyginai paprastas sparno projektavimo metodas, kurio tikslumas būtų pagrindžiamas sparno profilių matavimo rezultatais aerodinaminiame vamzdyje. Mažų grei��ių orlaivio projektavimo procese tiesioginių sparno matavimų rezultatų aerodinaminiame vamzdyje panaudojimas yra apribotas, nes dėl didelės sparnų įvairovės kiekvieno sparno atveju būtina atlikti unikalius kompleksinius matavimus. Čia išvardintos aplinkybės sudarė sąlygas pradėti tyrimus, skirtus pritaikyti matavimų inžinerijoje naudojamus matavimų metodus matematiškai modeliuojant orlaivio sparno aerodinamines jėgas. / Dissertation presents a method of aircraft wing modeling. The method combines wing modeling by means of flat elements and horseshoe-shaped vortices with an algorithm what takes into consideration non-linear characteristics of wing airfoils. This algorithm provides for a possibility of using the results of both numerical and measurement results in calculation of aerodynamic forces of a wing. A methodology is included to evaluate convergence of the calculation process and to establish conditions of reliability of the results. Calculation results are presented for lift and drag force coefficients of 24 different wings. These results are compared with the results obtained by other authors and measurement results in wind tunnel. Dissertation consists of Introduction, 4 chapters, Conclusions, List of Literature, List of Publications and Addendum. The total scope of the dissertation - 90 pages, 96 pictures, 1 table and 1 addendum.

The aim of this research is to develop and examine a method for analysis of aerodynamic parameters of the aircraft wing based on the airfoil measurement results and mathematical simulation using non-linear characteristics of airfoils constituting the wing. / Pilotuojamiems orlaiviams keliami vienodi skrydžio saugumo reikalavimai nepriklausomai nuo jų dydžio ir skrydžio greičio. Sparčiai vystantis mažų greičių aviacijai aktualu mažinti tokių orlaivių projektavimo, gamybos ir bandymų išlaidas išlaikant tą patį skrydžio saugumo lygį. Kadangi orlaivio skrydžio savybes daugiausia nulemia sparno aerodinaminės savybės, ypač aktualu pigiai ir greitai kurti sparnus mažų greičių orlaiviui. Tam reikalingas patikimas, sąlyginai paprastas sparno projektavimo metodas, kurio tikslumas būtų pagrindžiamas sparno profilių matavimo rezultatais aerodinaminiame vamzdyje. Mažų greičių orlaivio projektavimo procese tiesioginių sparno matavimų rezultatų aerodinaminiame vamzdyje panaudojimas ribotas, nes dėl didelės sparnų įvairovės kiekvieno sparno atveju būtina atlikti unikalius kompleksinius matavimus. Čia išvardintos aplinkybės sudarė sąlygas pradėti tyrimus, skirtus pritaikyti matavimų inžinerijoje naudojamus matavimų metodus matematiškai modeliuojant orlaivio sparno aerodinamines jėgas.

Motivated by a practical interest in noise generated by turbofan engine, this thesis studies the stability of parallel coaxial jets with velocity and temperature profiles characteristic of the exhaust region of the engine. Because the bypass stream mixes with both the exhaust and the ambient air, these profiles contain thin layers in which the velocity and temperature may vary rapidly. As a consequence, multiple instability modes are possible. In accordance with Rayleigh's theorem for axisymmetric incompressible shear flows, it follows that there are three possible modes, only two of which are unstable. To complement the study of parallel flow stability, this thesis also includes the derivation of the amplitude evolution equation for slowly varying axisymmetric incompressible flows.

Due to more and more aggressive designs in turbomachinery, assuring the structural integrity of its components has become challenging. Also influenced by this trend is blade design, where lighter and slimmer blades, in combination with higher loading, lead to an increased risk of failure, e.g. in the form of blade vibration. Methods have been proposed to reduce vibration amplitudes for subsonic engines, but cannot directly be applied to transonic regimes due to the additional physical phenomena involved. Therefore the present work investigates numerically the influence of two methods for reducing blade vibration amplitudes in transonic turbomachines, namely varying the blade count ratio and clocking. As it is known that clocking affects the efficiency, the concurrent effects on vibration amplitudes and efficiency are analyzed and discussed in detail. For the computational investigations, the proprietary Fortran-based non-linear, viscous 3D-CFD solver VolSol is applied on two transonic compressor cases and one transonic turbine case. In order to reduce calculation time and to generate the different blade count ratios a scaling technique is applied. The first and main part of this work focuses on the influence of the reduction techniques on aerodynamic forcing. Both the change in blade count ratio and clocking position are found to have significant potential for reducing aerodynamic force amplitudes. Manipulation of the phasing of excitation sources is found herein to be a major contributor to the amplitude variation. The lowest stimulus results are achieved for de-phased excitation sources and results in multiple blade force peaks per blade passing. In the case of blade count ratio variation it was found that blockage for high blade count ratios and the change in potential field size have significant impacts on the blade forcing. For the clocking investigation, three additional operating points and blade count ratios are analyzed and prove to have an impact on the force reduction achievable by clocking. The second part of the work evaluates the influence of clocking on the efficiency of a transonic compressor. It is found that the efficiency can be increased, but the magnitude of the change and the optimal wake impingement location depend on the operating point. Moreover it is shown that optimal efficiency and aerodynamic forcing settings are not directly related. In order to approximate the range of changes of both parameters, an ellipse approximation is suggested. / <p>QC 20130911</p> / TURBOPOWER

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Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2009) Includes bibliographical references.