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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781725081031
Category :
Languages : en
Pages : 28
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Book Description
The study of dynamic stall of rapidly pitching airfoils is being conducted at NASA Ames Research Center. Understanding this physical phenomenon will aid in improving the maneuverability of fighter aircraft as well as civilian aircraft. A wind tunnel device which can linearly pitch and control an airfoil with rapid dynamic response is needed for such tests. To develop a mechanism capable of high accelerations, an accurate model and control system is created. The model contains mathematical representations of the mechanical system, including mass, spring, and damping characteristics for each structural element, as well as coulomb friction and servovalve saturation. Electrical components, both digital and analog, linear and nonlinear, are simulated. The implementation of such a high-performance system requires detailed control design as well as state-of-the-art components. This paper describes the system model, states the system requirements, and presents results of its theoretical performance which maximizes the structural and hydraulic aspects of this system. Andrews, Daniel R. Ames Research Center NASA-TM-101076, A-89051, NAS 1.15:101076 RTOP 505-61-51...
Author: Daniel R. Andrews
Publisher:
ISBN:
Category :
Languages : en
Pages : 13
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Book Description
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781725081031
Category :
Languages : en
Pages : 28
Get Book Here
Book Description
The study of dynamic stall of rapidly pitching airfoils is being conducted at NASA Ames Research Center. Understanding this physical phenomenon will aid in improving the maneuverability of fighter aircraft as well as civilian aircraft. A wind tunnel device which can linearly pitch and control an airfoil with rapid dynamic response is needed for such tests. To develop a mechanism capable of high accelerations, an accurate model and control system is created. The model contains mathematical representations of the mechanical system, including mass, spring, and damping characteristics for each structural element, as well as coulomb friction and servovalve saturation. Electrical components, both digital and analog, linear and nonlinear, are simulated. The implementation of such a high-performance system requires detailed control design as well as state-of-the-art components. This paper describes the system model, states the system requirements, and presents results of its theoretical performance which maximizes the structural and hydraulic aspects of this system. Andrews, Daniel R. Ames Research Center NASA-TM-101076, A-89051, NAS 1.15:101076 RTOP 505-61-51...
Author: JoAnn L. Gravitt
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 144
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Author: Christopher Eldon Whitmer
Publisher:
ISBN:
Category :
Languages : en
Pages : 282
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The aeroelastic modeling and robust control design for a morphing airfoil concept is presented. A finite dimensional linear time invariant aeroelastic model was developed for a multi-input, multi-output morphing airfoil structure. The shape of the airfoil (NACA airfoil series 2415) was controlled by actuators distributed along the top airfoil surface that produced vertical deflections of the top surface at several locations. The resulting airfoil shape change caused changes in the aerodynamic loading on the wing. The primary objective of this thesis was to control the deformation of the airfoil to achieve desirable aerodynamic forces on the wing. The structural model was developed using a finite element approach. A finite element toolbox in Matlab (FEMLAB) was used to obtain eigenfrequencies and mode shapes. A finite dimensional dynamic model of the structure was then obtained by the assumed modes method. A static aerodynamic model was developed with a vortex lattice method and coupled with the structural dynamic model to yield a linear aeroelastic model of the morphing wing. The developed control model is presented along with robust designs that controlled the deformation of the airfoil. Robust LQG, H[subscript infinity], McFarlane Glover, and mu-synthesis methods are described and control designs compared in the presence of additive, parametric, and input multiplicative uncertainties. Simulation results are given to demonstrate the viability of the proposed modeling and control methodology for morphing wing concept.
Author: Brian G. Allan
Publisher:
ISBN:
Category :
Languages : en
Pages : 22
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 39
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A high-order non-uniform compact finite-difference algorithm with numerical filtering and low storage Runga-Kutta scheme is developed to perform numerical simulations on orthogonal grids generated about plunging and pitching airfoils. The grids, which move with the pitching and plunging airfoil, are generated using "Streamfunction as a coordinate approach" (SFC). SFC is widely used in combination with lower-order schemes in Computational Fluid Dynamics. The straightforward implementation of SFC create rather coarse grid at the solution accuracy, non-uniform SFC grid with appropriate grid stretching and filtering of solution is implemented. The different kinds of SFC grid generation methods and the grid clustering in the vicinity of stagnation point are discussed. The applications of the developed grid generator and numerical solver to problems based on linearized Euler equations, for which analytical solutions are available, are shown first. Then, the methodology is applied to unsteady aerodynamics of pitching and plunging airfoils. The application of the developed grid generator and numerical solver to plunging airfoil problems are discussed and compared with available experimental data including lift force for plunging NACA0012 airfoil and visualization of vortical flowfield for plunging SD7003 airfoil. Finally, the use of flapping airfoil for control of gust-induced oscillations of airfoil lift force is discussed.
Author: Nurbaiti Wahid
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 108
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Author: Robert M. Bennett
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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As a portion of the Benchmark Models Program at NASA Langley (Ref I), three models with the same rectangular plankton, but with different airfoils were flutter tested on the Pitch and Plunge Apparatus (PAPA. Ref 2-3). These models were designed and tested to provide flutter data for evaluating Computational Aeroelasticity (CA) programs with emphasis on transonic flows The geometry of the wings was kept simple to reduce the complexity of the geometry processing for computation and in the interpretation of the results. One model was built with the NACA 0012 airfoil culled the B0012, one with the NACA 64A0lC airfoil called the B64AOlO. and one with an NASA SC(2)-0414 airfoil called BSCW. These airfoils, shown in Fig I, were not selected to provide a systematic empirical trend study of thickness or airfoil type, hut to provide flutter data for wings with different transonic airfoil characteristics. The NACA 0012 airfoil has a forward loading and for transonic flows, a shock long initially ahead of midchord. The NACA 64A010 airfoil has a more mild evolution of the shock which forms initially near midchord. The NASA SC(2)-0414 has a strong aft loading and the associated low oft upper surface. There was considerable experience in two dimensions with the NACA 0012 and 64A01C airfoils based on comparisons with the early two- dimensional unsteady aerodynamic data of Ref 4. The supercritical airfoil (Ref I) was chosen as a relatively modem airfoil for comparison.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 892
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Author:
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 1430
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