摘要 :
An experiment was conducted to study the aerodynamic response of a wing to large amplitude pitching motions, including dynamic stall. A two-dimensional model was tested at Mach numbers of 0.2, 0.3, and 0.4, corresponding to Reynol...
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An experiment was conducted to study the aerodynamic response of a wing to large amplitude pitching motions, including dynamic stall. A two-dimensional model was tested at Mach numbers of 0.2, 0.3, and 0.4, corresponding to Reynolds numbers between 2 x 1000000 and 4 x 1000000. A total of 49 unsteady conditions were studied, including both sinusoidal oscillations and constant pitch rate ramps. The ramp motions ranged up to 0 to 30 deg at pitch rates between 17.5 and 350 deg/sec. A preliminary analysis of the results shows significant effects of pitch rate and Mach number on the surface pressures, integrated airloads, and locations of boundary layer transition and separation. A pressure oscillation was detected in the post stall region that appears to result from periodic vortex shedding that has synchronized to the imposed pitching motion. A more detailed analysis of these results will be conducted during the remainder of this activity. Keywords: Unsteady aerodynamics; Dynamic stall; Aerodynamic testing; Unsteady measurement techniques.
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Unsteady aerodynamic methods adopted for the study of aeroelasticity in helicopters are considered with focus on the development of a semiempirical model of unsteady aerodynamic forces acting on an oscillating profile at high inci...
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Unsteady aerodynamic methods adopted for the study of aeroelasticity in helicopters are considered with focus on the development of a semiempirical model of unsteady aerodynamic forces acting on an oscillating profile at high incidence. The successive smoothing algorithm described leads to the model's coefficients in a very satisfactory manner.
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Analytical and experimental research in the area of unsteady aerodynamics of turbomachinery has conventionally been applied to blading which oscillates when placed in a uniformly flowing fluid. Comparatively less effort has been o...
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Analytical and experimental research in the area of unsteady aerodynamics of turbomachinery has conventionally been applied to blading which oscillates when placed in a uniformly flowing fluid. Comparatively less effort has been offered for the study of blading which is subjected to nonuniformities within the flow field. The fluid dynamic environment of a blade-row embedded within multi-stage turbomachines is dominated by such highly unsteady fluid flow conditions. The production of wakes and circumferential pressure variations from adjacent blade-rows causes large unsteady energy transfers between the fluid and the blades. Determination of the forced response of a blade requires the ability to predict the unsteady loads which are induced by these aerodynamic sources. A review of research publications was done to determine recent investigations of the response of turbomachinery blading subjected to aerodynamic excitations. Such excitations are a direct result of the blade-row aerodynamic interaction which occurs between adjacent cascades of blades. The reports and papers reviewed have been organized into areas emphasizing experimental or analytical efforts.
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摘要 :
Analytical and experimental research in the area of unsteady aerodynamics of turbomachinery has conventionally been applied to blading which oscillates when placed in a uniformly flowing fluid. Comparatively less effort has been o...
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Analytical and experimental research in the area of unsteady aerodynamics of turbomachinery has conventionally been applied to blading which oscillates when placed in a uniformly flowing fluid. Comparatively less effort has been offered for the study of blading which is subjected to nonuniformities within the flow field. The fluid dynamic environment of a blade-row embedded within multi-stage turbomachines is dominated by such highly unsteady fluid flow conditions. The production of wakes and circumferential pressure variations from adjacent blade-rows causes large unsteady energy transfers between the fluid and the blades. Determination of the forced response of a blade requires the ability to predict the unsteady loads which are induced by these aerodynamic sources. A review of research publications was done to determine recent investigations of the response of turbomachinery blading subjected to aerodynamic excitations. Such excitations are a direct result of the blade-row aerodynamic interaction which occurs between adjacent cascades of blades. The reports and papers reviewed have been organized into areas emphasizing experimental or analytical efforts.
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This report summarizes the status of computational unsteady aerodynamics methods for aeroelastic analysis and makes recommendations for future research activities. The flight conditions for which various types of flows exist are d...
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This report summarizes the status of computational unsteady aerodynamics methods for aeroelastic analysis and makes recommendations for future research activities. The flight conditions for which various types of flows exist are described and the aeroelastic phenomena that can occur in those flight regimes are discussed. Some important aeroelastic problems of current interest are described, and the aerodynamic methods needed to analyze them are presented. The capabilities and limitations of existing unsteady aerodynamics methods are discussed. Computer resources required to perform aeroelastic analysis of various flight vehicle configurations are presented. Recommendations for future research are made, and schedules for completion of proposed research tasks are presented.
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This paper presents a general method for investigating the unsteady aerodynamics of flapping wings for micro air vehicle application. For this purpose, a dynamically scaled robotic flapper was designed and fabricated which can fla...
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This paper presents a general method for investigating the unsteady aerodynamics of flapping wings for micro air vehicle application. For this purpose, a dynamically scaled robotic flapper was designed and fabricated which can flap the wings in a desired kinematic pattern. A quasisteady aerodynamic model and wing testing methodology was developed based on unsteady aerodynamic mechanisms. This model additionally accounts for the wing twisting. The experimental results show a good agreement with published data. 24 kinematic patterns were tested and the quasi-steady aerodynamic model compares well with the experimental results. The focus of the present work is on hovering flight, however, the methodology is general and can be extended to slow forward flight in future.
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Future vehicle designs will see a paradigm shift from: 1) Steady to the unsteady world (e.g. flow control, adaptive morphing); 2) Passive to active; 3) Rigid designs to exploitation of flexibility and adaptability; 4) Few discrete...
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Future vehicle designs will see a paradigm shift from: 1) Steady to the unsteady world (e.g. flow control, adaptive morphing); 2) Passive to active; 3) Rigid designs to exploitation of flexibility and adaptability; 4) Few discrete to numerous distributed (e.g. sensors, control surfaces); 5) To obtain a vehicle that is always at optimum performance. Therefore, future designs will be inherently multidisciplinary, and the greatest technical challenges and opportunities occur at the intersection of disciplines COMSAC appears to be a step towards enabling the future vision.
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A simple vortex system is used to model unsteady aerodynamic effects into the rigid-body longitudinal equations of motion of an aircraft. With the formulation used, only steady-state aerodynamic derivatives appear in the equations...
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A simple vortex system is used to model unsteady aerodynamic effects into the rigid-body longitudinal equations of motion of an aircraft. With the formulation used, only steady-state aerodynamic derivatives appear in the equations. It is found expedient to transform the equations into the frequency domain to make them useful for extracting aerodynamic parameters from flight data. The equations are used in the development of a parameter-extraction algorithm. If the algorithm is used with the unsteady aerodynamic modeling included, all extracted aerodynamic derivatives are the steady-state derivatives. If unsteady aerodynamic modeling is omitted, some extracted parameters include the effects of unsteady aerodynamics and are interpreted as combinations of steady-state and acceleration parameters. Use of the two parameter-estimation modes, one including and the other omitting unsteady-aerodynamic modeling, provides a means of estimating some acceleration derivatives. Computer-generated data and flight data are used to demonstrate the use of the parameter-extraction algorithm.
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