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- Hirschel, Ernst Heinrich, et al.
(författare)
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Separated and Vortical Flow in Aircraft Wing Aerodynamics : Basic Principles and Unit Problems
- 2020
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Fluid mechanical aspects of separated and vortical flow in aircraft wing aerodynamics are treated. The focus is on two wing classes: (1) large aspect-ratio wings and (2) small aspect-ratio delta-type wings. Aerodynamic design issues in general are not dealt with. Discrete numerical simulation methods play a progressively larger role in aircraft design and development. Accordingly, in the introduction to the book the different mathematical models are considered, which underlie the aerodynamic computation methods (panel methods, RANS and scale-resolving methods). Special methods are the Euler methods, which as rather inexpensive methods embrace compressibility effects and also permit to describe lifting-wing flow. The concept of the kinematically active and inactive vorticity content of shear layers gives insight into many flow phenomena, but also, with the second break of symmetry---the first one is due to the Kutta condition---an explanation of lifting-wing flow fields. The prerequisite is an extended definition of separation: “flow-off separation” at sharp trailing edges of class (1) wings and at sharp leading edges of class (2) wings. The vorticity-content concept, with a compatibility condition for flow-off separation at sharp edges, permits to understand the properties of the evolving trailing vortex layer and the resulting pair of trailing vortices of class (1) wings. The concept also shows that Euler methods at sharp delta or strake leading edges of class (2) wings can give reliable results. Three main topics are treated: 1) Basic Principles are considered first: Boundary-layer flow, vortex theory, the vorticity content of shear layers, Euler solutions for lifting wings, the Kutta condition in reality and the topology of skin-friction and velocity fields. 2) Unit Problems treat isolated flow phenomena of the two wing classes. Capabilities of panel and Euler methods are investigated. One Unit Problem is the flow past the wing of the NASA Common Research Model. Other Unit Problems concern the lee-side vortex system appearing at the Vortex-Flow Experiment 1 and 2 sharp- and blunt-edged delta configurations, at a delta wing with partly round leading edges, and also at the Blunt Delta Wing at hypersonic speed. 3) Selected Flow Problems of the two wing classes. In short sections practical design problems are discussed. The treatment of flow past fuselages, although desirable, was not possible in the frame of this book.
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| 2. |
- Bannova, Olga, 1964
(författare)
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Space Architecture Education for Engineers and Architects
- 2016
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- This book considers two key educational tools for future generations of professionals with a space architecture background in the 21st century: (1) introducing the discipline of space architecture into the space system engineering curricula; and (2) developing space architecture as a distinct, complete training curriculum. Professionals educated this way will help shift focus from solely engineering-driven transportation systems and “sortie” missions towards permanent off-world human presence. The architectural training teaches young professionals to operate at all scales from the “overall picture” down to the smallest details, to provide directive intention–not just analysis–to design opportunities, to address the relationship between human behavior and the built environment, and to interact with many diverse fields and disciplines throughout the project lifecycle. This book will benefit individuals and organizations responsible for planning transportation and habitat systems in space, while also providing detailed information on work and design processes for architects and engineers.
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| 4. |
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| 5. |
- Kirkwood, S., et al.
(författare)
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Polar mesosphere winter echoes by ESRAD, EISCAT and lidar
- 2002
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- The ESRAD 52 MHz MST radar (67° 53 ‘ N, 21 ° 06 ‘ E) has observed thin layers of enhanced radar echoes in the winter mesosphere during several recent solar proton events. The detection of these polar mesosphere winter echoes (PMWE) is generally found to correlates well with low values of λ (the ratio of negative ion density to electron density). However PMWE are found to persist for values of λ up to ~100. Present knowledge of the nature of neutral turbulence in the winter mesosphere suggests that such turbulence cannot generate electron density fluctuations with scale-sizes as short as the 3 m needed to produce radar echoes at 52 MHz. This is particularly true as λ increases to ~100. Joint observations from ESRAD and the EISCAT 224 MHz radar suggest that PMWE is also detectable at 67 cm scale-sizes, further increasing the difficulty in explaining the echoes by neutral turbulence. Joint observations from ESRAD and lidar are also inconsistent with the expected behaviour of turbulence. Together with results concerning the thickness, echo aspect-sensitivity and echo spectral-width of the PMWE, these observation leads to the conclusion that the layers cannot be explained by turbulence alone. A role for charged aerosols in creating PMWE is proposed. The presence of aerosols is supported by the lidar observations.
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| 7. |
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| 8. |
- Melin, Tomas, 1975-
(författare)
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Parametric Airfoil Catalog Part I, Archer A18 to Göttingen 655 : An Aerodynamic and Geometric Comparison Between Parametrized and Point Cloud Airfoils
- 2013. - 1
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- A fundamental part of aircraft design involves wing airfoiloptimization, establishing an outer shape of the wing which has good aerodynamic performance for the design mission, good internal volume distribution for fuel and systems and which also serves as an efficient structural member supporting the load of the weight of the aircraft. The underlying idea with this parametrization is to couple an appropriate number of parameters, balancing the need of geometric accuracy with the necessity of few airfoil parameters in order to facilitate en expedient optimisation, with the intrinsic value of having parameters that makes sense for a human; such as thickness, camber and trailing edge thickness. Several approaches to parametrization of wing proles can be found in the literature. Airfoils can be described by point clouds as done in most airfoil libraries. The number of parameters is twice as large as the number of points used (x and y coordinates) and in the case of aerodynamic optimization this parametrization will most certainly be not well behaved, since no smoothing function is included and must therefore be employed. Other problems may arise for the fact that the airfoils sometimes are defined with too few coordinate points and/or too few decimals, a problem occurring especially with old airfoils. On the other hand, the design space that this kind of parametrization allows representing is extremely large, as any and all shapes can be reproduced, even degenerate ones. Airfoils can also be represented by mathematical functions. Among the most common representatives of thiscategory are indeed the NACA 4-, 5- and 6-digits formulations. Compared to point clouds, they could be said to represent the opposite case: they are very well behaving parametrizations, but they cannot cover avery large design space, since they only provide four to six parameters respectively to be tuned. The NACA 4digit series is particularly interesting as the parametersare a part of the name of the airfoil. In the case of the 5- and 6 digit series, the name is instead constructed from the airfoils aerodynamic characteristic and geometry. Another known set of theoretically defined airfoils are the Joukowski profiles [4]. Using the conformal mapping method, airfoils with a round nose and sharp trailing edge can be represented. Sadly the method is not to recommend for trying to match known airfoils and the design space it describes is quite confined to airfoils with often poor performances.
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| 9. |
- Melin, Tomas, 1975-
(författare)
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Parametric Airfoil Catalog, Part II: Göttingen 673 to YS930 : An Aerodynamic and Geometric Comparison Between Parametrized and Point Cloud Airfoils
- 2013
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- A fundamental part of aircraft design involves wing airfoiloptimization, establishing an outer shape of the wing which has good aerodynamic performance for the design mission, good internal volume distribution for fuel and systems and which also serves as an efficient structural member supporting the load of the weight of the aircraft. The underlying idea with this parametrization is to couple an appropriate number of parameters, balancing the need of geometric accuracy with the necessity of few airfoil parameters in order to facilitate en expedient optimisation, with the intrinsic value of having parameters that makes sense for a human; such as thickness, camber and trailing edge thickness. Several approaches to parametrization of wing proles can be found in the literature. Airfoils can be described by point clouds as done in most airfoil libraries. The number of parameters is twice as large as the number of points used (x and y coordinates) and in the case of aerodynamic optimization this parametrization will most certainly be not well behaved, since no smoothing function is included and must therefore be employed. Other problems may arise for the fact that the airfoils sometimes are defined with too few coordinate points and/or too few decimals, a problem occurring especially with old airfoils. On the other hand, the design space that this kind of parametrization allows representing is extremely large, as any and all shapes can be reproduced, even degenerate ones. Airfoils can also be represented by mathematical functions. Among the most common representatives of thiscategory are indeed the NACA 4-, 5- and 6-digits formulations. Compared to point clouds, they could be said to represent the opposite case: they are very well behaving parametrizations, but they cannot cover avery large design space, since they only provide four to six parameters respectively to be tuned. The NACA 4digit series is particularly interesting as the parametersare a part of the name of the airfoil. In the case of the 5- and 6 digit series, the name is instead constructed from the airfoils aerodynamic characteristic and geometry. Another known set of theoretically defined airfoils are the Joukowski profiles [4]. Using the conformal mapping method, airfoils with a round nose and sharp trailing edge can be represented. Sadly the method is not to recommend for trying to match known airfoils and the design space it describes is quite confined to airfoils with often poor performances.
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