Development of a Simulation and Optimization Framework for Improved Aerodynamic Performance of R/C Helicopter Rotor Blades PDF Download
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Author: Jonathan Wiebe
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Category :
Languages : en
Pages :
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Author: Jonathan Wiebe
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Category :
Languages : en
Pages :
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Author: Kyle Brian Collins
Publisher:
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Category : Aerodynamics
Languages : en
Pages :
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New helicopter rotor designs are desired that offer increased efficiency, reduced vibration, and reduced noise. This problem is multidisciplinary, requiring knowledge of structural dynamics, aerodynamics, and aeroacoustics. Rotor optimization requires achieving multiple, often conflicting objectives. There is no longer a single optimum but rather an optimal trade-off space, the Pareto Frontier. Rotor Designers in industry need methods that allow the most accurate simulation tools available to search for Pareto designs. Computer simulation and optimization of rotors have been advanced by the development of "comprehensive" rotorcraft analysis tools. These tools perform aeroelastic analysis using Computational Structural Dynamics (CSD). Though useful in optimization, these tools lack built-in high fidelity aerodynamic models. The most accurate rotor simulations utilize Computational Fluid Dynamics (CFD) coupled to the CSD of a comprehensive code, but are generally considered too time consuming where numerous simulations are required like rotor optimization. An approach is needed where high fidelity CFD/CSD simulation can be routinely used in design optimization. This thesis documents the development of physics based rotor simulation frameworks. A low fidelity model uses a comprehensive code with simplified aerodynamics. A high fidelity model uses a parallel processor capable CFD/CSD methodology. Both frameworks include an aeroacoustic simulation for prediction of noise. A synergistic process is developed that uses both frameworks together to build approximate models of important high fidelity metrics as functions of certain design variables. To test this process, a 4-bladed hingeless rotor model is used as a baseline. The design variables investigated include tip geometry and spanwise twist. Approximation models are built for high fidelity metrics related to rotor efficiency and vibration. Optimization using the approximation models found the designs having maximum rotor efficiency and minimum vibration. Various Pareto generation methods are used to find frontier designs between these two anchor designs. The Pareto anchors are tested in the high fidelity simulation and shown to be good designs, providing evidence that the process has merit. Ultimately, this process can be utilized by industry rotor designers with their existing tools to bring high fidelity analysis into the preliminary design stage of rotors.
Author: John D. Berry
Publisher:
ISBN:
Category : Rotors (Helicopters)
Languages : en
Pages : 54
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A test to determine the performance differences between the 27-percent-scale models of two rotors for the U.S. Army AH-64 helicopter was conducted in the Langley 14- by 22-Foot Subsonic Tunnel. One rotor, referred to as the baseline rotor, simulated the geometry and dynamic characteristics of the production baseline rotor, and the other rotor, referred to as the advanced rotor, was designed to have improved hover performance. During the performance test, the dynamic pitch-link forces and blade bending and torsion moments were also measured. Dynamic data from the forward flight investigation have been reduced and are presented herein. The advanced blade set was designed to have dynamic characteristics similar to those of the baseline rotor so that test conditions would not be limited by potential rotor instability and blade resonances and so that the measured performance increments could be considered to be due purely to aerodynamic causes. Data show consistent trends with advance ratio for both blade sets with generally higher oscillatory loads occurring for the advanced blade set when compared with the baseline blade set.
Author:
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Category :
Languages : en
Pages : 30
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Author:
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ISBN:
Category :
Languages : en
Pages : 134
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Data for rotors using unconventional airfoils are of interest to permit an evaluation of this technology's capability to meet the U.S. Army's need for increased helicopter mission effectiveness and improved safety and survivability. Thus, an experimental investigation was conducted in the Langley Transonic Dynamics Tunnel (TDT) to evaluate the effect of using slotted airfoils in the rotor blade tip region (85 to 100 percent radius) on rotor aerodynamic performance and loads. Four rotor configurations were tested in forward flight at advance ratios from 0.15 to 0.45 and in hover in-ground effect. The hover tip Mach number was 0.627, which is representative of a design point of 4000-ft geometric altitude and a temperature of 95 degrees F. The baseline rotor configuration had a conventional single element airfoil in the tip region. A second rotor configuration had a forward-slotted airfoil with a -6 degrees slat, a third configuration had a forward-slotted airfoil with a -10 degrees slat, and a fourth configuration had an aft-slotted airfoil with a 3 degrees flap (trailing edge down). The results of this investigation indicate that the -6 degrees slat configuration offers some performance and loads benefits over the other three configurations.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 88
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Author: Aditi Chattopadhyay
Publisher:
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Category : Aerodynamic load
Languages : en
Pages : 24
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722904371
Category :
Languages : en
Pages : 182
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A higher-order theory is developed to model composite box beams with arbitrary wall thicknesses. The theory, based on a refined displacement field, represents a three-dimensional model which approximates the elasticity solution. Therefore, the cross-sectional properties are not reduced to one-dimensional beam parameters. Both inplane and out-of-plane warping are automatically included in the formulation. The model accurately captures the transverse shear stresses through the thickness of each wall while satisfying all stress-free boundary conditions. Several numerical results are presented to validate the present theory. The developed theory is then used to model the load carrying member of a tilt-rotor blade which has thick-walled sections. The composite structural analysis is coupled with an aerodynamic analysis to compute the aeroelastic stability of the blade. Finally, a multidisciplinary optimization procedure is developed to improve the aerodynamic, structural and aeroelastic performance of the tilt-rotor aircraft. The Kreisselmeier-Steinhauser function is used to formulate the multiobjective function problem and a hybrid approximate analysis is used to reduce the computational effort. The optimum results are compared with the baseline values and show significant improvements in the overall performance of the tilt-rotor blade. McCarthy, Thomas Robert Ames Research Center TILT ROTOR AIRCRAFT; THREE DIMENSIONAL MODELS; MULTIDISCIPLINARY DESIGN OPTIMIZATION; ROTARY WINGS; COMPOSITE STRUCTURES; MATHEMATICAL MODELS; AERODYNAMIC LOADS; AEROELASTICITY; BOX BEAMS; TRANSVERSE LOADS; THICK WALLS; STRUCTURAL ANALYSIS; PROPELLER BLADES; SHEAR STRESS; ELASTIC PROPERTIES; STRESS-STRAIN RELATIONSHIPS; RESONANT FREQUENCIES; HIGH SPEED...
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 46
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Author: W. J. McCroskey
Publisher:
ISBN:
Category : Wakes (Aerodynamics)
Languages : en
Pages : 38
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Aerodynamic research relating to modern helicopters includes the study of three-dimensional, unsteady, nonlinear flow fields. A selective review is made of some of the phenomenon that hamper the development of satisfactory engineering prediction techniques, but which provides a rich source of research opportunities: flow separations, compressibility effects, complex vortical wakes, and aerodynamic interference between components. Several examples of work in progress are given, including dynamic stall alleviation, the development of computational methods for transonic flow, rotor-wake predictions, and blade-vortex interactions. (Author).
