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  • 1
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    Eigenvalue calculation procedure for an Euler/Navier-stokes solver with application to flows over airfoils (1991)
    Elsevier
    Details
    Publication Date: 1991-04-01
    Print ISSN: 0021-9991
    Electronic ISSN: 1090-2716
    Topics: Computer Science , Physics
    Published by Elsevier
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    PAPER CURRENT
  • 2
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    Eigenvalue calculation procedure for an Euler/Navier-Stokes solver with application to flows over airfoils (1991)
    Elsevier
    Details
    Publication Date: 1991-12-01
    Print ISSN: 0021-9991
    Electronic ISSN: 1090-2716
    Topics: Computer Science , Physics
    Published by Elsevier
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    PAPER CURRENT
  • 3
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    Cascade flutter analysis with transient response aerodynamics (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Two methods for calculating linear frequency domain aerodynamic coefficients from a time-marching Full-Potential cascade solver are developed and verified. In the first method, the Influence Coefficient method, solutions to elemental problems are superposed to obtain the solutions for a cascade in which all blades are vibrating with a constant interblade phase angle. The elemental problem consists of a single blade in the cascade oscillating while the other blades remain stationary. In the second method, the Pulse Response method, the response to the transient motion of a blade is used to calculate influence coefficients. This is done by calculating the Fourier transforms of the blade motion and the response. Both methods are validated by comparison with the Harmonic Oscillation method and give accurate results. The aerodynamic coefficients obtained from these methods are used for frequency domain flutter calculations involving a typical section blade structural model. An eigenvalue problem is solved for each interblade phase angle mode and the eigenvalues are used to determine aeroelastic stability. Flutter calculations are performed for two examples over a range of subsonic Mach numbers using both flat plates and actual airfoils.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 91-0747
    Format: text
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  • 4
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    Cascade flutter analysis with transient response aerodynamics (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Two methods for calculating linear frequency domain aerodynamic coefficients from a time marching Full Potential cascade solver are developed and verified. In the first method, the Influence Coefficient, solutions to elemental problems are superposed to obtain the solutions for a cascade in which all blades are vibrating with a constant interblade phase angle. The elemental problem consists of a single blade in the cascade oscillating while the other blades remain stationary. In the second method, the Pulse Response, the response to the transient motion of a blade is used to calculate influence coefficients. This is done by calculating the Fourier Transforms of the blade motion and the response. Both methods are validated by comparison with the Harmonic Oscillation method and give accurate results. The aerodynamic coefficients obtained from these methods are used for frequency domain flutter calculations involving a typical section blade structural model. An eigenvalue problem is solved for each interblade phase angle mode and the eigenvalues are used to determine aeroelastic stability. Flutter calculations are performed for two examples over a range of subsonic Mach numbers.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-103746 , E-5991 , NAS 1.15:103746
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Semi-empirical model for prediction of unsteady forces on an airfoil with application to flutter (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A semi-empirical model is described for predicting unsteady aerodynamic forces on arbitrary airfoils under mildly stalled and unstalled conditions. Aerodynamic forces are modeled using second order ordinary differential equations for lift and moment with airfoil motion as the input. This model is simultaneously integrated with structural dynamics equations to determine flutter characteristics for a two degrees-of-freedom system. Results for a number of cases are presented to demonstrate the suitability of this model to predict flutter. Comparison is made to the flutter characteristics determined by a Navier-Stokes solver and also the classical incompressible potential flow theory.
    Keywords: AERODYNAMICS
    Type: NASA-TM-105414 , E-6820 , NAS 1.15:105414
    Format: application/pdf
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  • 6
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    Aeroelastic stability analyses of two counter rotating propfan designs for a cruise missile model (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Aeroelastic stability analyses were performed to insure structural integrity of two counterrotating propfan blade designs for a NAVY/Air Force/NASA cruise missile model wind tunnel test. This analysis predicted if the propfan designs would be flutter free at the operating conditions of the wind tunnel test. Calculated stability results are presented for the two blade designs with rotational speed and Mach number as the parameters. A aeroelastic analysis code ASTROP2 (Aeroelastic Stability and Response of Propulsion Systems - 2 Dimensional Analysis), developed at LeRC, was used in this project. The aeroelastic analysis is a modal method and uses the combination of a finite element structural model and two dimensional steady and unsteady cascade aerodynamic models. This code was developed to analyze single rotation propfans but was modified and applied to counterrotating propfans for the present work. Modifications were made to transform the geometry and rotation of the aft rotor to the same reference frame as the forward rotor, to input a non-uniform inflow into the rotor being analyzed, and to automatically converge to the least stable aeroelastic mode.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-105268 , E-7001 , NAS 1.15:105268
    Format: application/pdf
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  • 7
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    An efficient procedure for cascade aeroelastic stability determination using nonlinear, time-marching aerodynamic solvers (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A numerical eigenvalue problem formulation and a practical calculation procedure for exact eigenvalues and corresponding eigenvectors are developed and applied to a nonlinear, two-dimensional, time-marching full potential solver for cascade aeroelastic stability analysis. This procedure is based on the Lanczos recursive method and it directly calculates stability information about a nonlinear steady state. It is compared to conventional approaches in the frequency and time domains developed earlier and is found to be 100-10.000 times more computationally efficient. Eigenvalue constellations and the flutter results for flow through a cascade SR5 propfan airfoil are presented.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 93-1631 , In: AIAA(ASME)ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 34th and AIAA/ASME Adaptive Structures Forum, La Jolla, CA, Apr. 19-22, 1993, Technical Papers. Pt. 5 (A93-33876 1; p. 2856-2866.
    Format: text
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  • 8
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    Reduced order models for nonlinear aerodynamics (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Reduced order models are needed for reliable, efficient and accurate prediction of aerodynamic forces to analyze fluid structure interaction problems in turbomachinery, including propfans. Here, a finite difference, time marching Navier-Stokes code is validated for unsteady airfoil motion by comparing results with those from classical potential flow. The Navier-Stokes code is then analyzed for calculation of primitive and exact estimates of eigenvalues and eigenvectors associated with fluid-airfoil interaction. A variational formulation for the Euler equations and Navier-Stokes equations will be the basis for reduction of order through an eigenvector transformation.
    Keywords: AERODYNAMICS
    Type: NASA, Lewis Research Center, Lewis Structures Technology, 1988. Volume 1: Structural Dynamics; p 299-308
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Eigenvalue calculation procedure for an Euler/Navier-Stokes solver with application to flows over airfoils (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A Lanczos procedure is presently applied to a Navier-Stokes (N-S) solver for eigenvalues and eigenvectors associated with the small-perturbation analysis of the N-S equations' finite-difference representation for airfoil flows; the matrix used is very large, sparse, real, and nonsymmetric. The Lanczos procedure is shown to furnish complete spectral information for the eigenvalues, as required for transient-stability analysis of N-S solvers.
    Keywords: AERODYNAMICS
    Type: Journal of Computational Physics (ISSN 0021-9991); 97; 398-413
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Aeroelastic stability analyses of two counter rotating propfan designs for a cruise missile model (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A modal aeroelastic analysis combining structural and aerodynamic models is applied to counterrotating propfans to evaluate their structural integrity for wind-tunnel testing. The aeroelastic analysis code is an extension of the 2D analysis code called the Aeroelastic Stability and Response of Propulsion Systems. Rotational speed and freestream Mach number are the parameters for calculating the stability of the two blade designs with a modal method combining a finite-element structural model with 2D steady and unsteady cascade aerodynamic models. The model demonstrates convergence to the least stable aeroelastic mode, describes the effects of a nonuniform inflow, and permits the modification of geometry and rotation. The analysis shows that the propfan designs are suitable for the wind-tunnel test and confirms that the propfans should be flutter-free under the range of conditions of the testing.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 92-2218 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 13, 1992 - Apr 15, 1992; Dallas, TX; United States
    Format: text
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