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  • 1
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    Nonlinear Stability and Response of Lifting Surfaces Via Volterra Series (2001)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This investigation concerns the time and frequency formulations of non-linear two-dimensional lifting surfaces exposed to an incompressible flow field and subjected to an external pressure pulse. In order to address this problem, Volterra series approach in conjunction with the multidimensional Laplace transform is used. This methodology enabling one to solve the aeroelastic governing equations of lifting surfaces opens the way to connect this methodology with that based on neural networks and NARMAX/NARX networks models. Moreover, this extended way to address this problem constitutes a good basis for treatment of the theory of 3D lifting surfaces.
    Keywords: Aerodynamics
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  • 2
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    Reduced Order Models Based on Linear and Nonlinear Aerodynamic Impulse Responses (1999)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: This paper discusses a method for the identification and application of reduced-order models based on linear and nonlinear aerodynamic impulse responses. The Volterra theory of nonlinear systems and an appropriate kernel identification technique are described. Insight into the nature of kernels is provided by applying the method to the nonlinear Riccati equation in a non-aerodynamic application. The method is then applied to a nonlinear aerodynamic model of an RAE 2822 supercritical airfoil undergoing plunge motions using the CFL3D Navier-Stokes flow solver with the Spalart-Allmaras turbulence model. Results demonstrate the computational efficiency of the technique.
    Keywords: Aerodynamics
    Type: CEAS/AIAA/ICASE/NASA Langley International Forum on Aeroelasticity and Structural Dynamics 1999; Pt. 1; 369-380; NASA/CP-1999-209136/PT1
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  • 3
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    Improving CAP-TSD steady pressure solutions through airfoil slope modification (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A modification of airfoil section geometry is examined for improvement of the leading edge pressures predicted by the Computational Aeroelasticity Program - Transonic Small Disturbance (CAP-TSD). Results are compared with Eppler solutions to assess improvement. Preliminary results indicate that a fading function modification of section slopes is capable of significant improvements in the pressures near the leading edge computed by CAP-TSD. Application of this modification to airfoil geometry before use in CAP-TSD is shown to reduce the nonphysical pressure peak predicted by the transonic small disturbance solver. A second advantage of the slope modification is the substantial reduction in sensitivity of CAP-TSD steady pressure solutions to the computational mesh.
    Keywords: Aerodynamics
    Type: NASA-TM-110214 , NAS 1.15:110214
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  • 4
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    AEROM: NASA's Unsteady Aerodynamic and Aeroelastic Reduced-Order Modeling Software (2018)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The origins, development, implementation, and application of AEROM, NASA's patented reduced-order modeling (ROM) software, are presented. Full computational fluid dynamic (CFD) aeroelastic solutions and ROM aeroelastic solutions, computed at several Mach numbers using the NASA FUN3D CFD code, are presented in the form of root locus plots in order to better reveal the aeroelastic root migrations with increasing dynamic pressure. The method and software have been applied successfully to several con figurations including the Lockheed-Martin N+2 supersonic configuration and the Royal Institute of Technology (KTH, Sweden) generic wind-tunnel model, among others. The software has been released to various organizations with applications that include CFD-based aeroelastic analyses and the rapid modeling of high- fidelity dynamic stability derivatives. Recent results obtained from the application of the method to the AGARD 445.6 wing will be presented that reveal several interesting insights.
    Keywords: Aerodynamics
    Type: NF1676L-29554 , Aerospace (e-ISSN 2226-4310); 5; 2
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  • 5
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    Development of Reduced-Order Models for Aeroelastic and Flutter Prediction Using the CFL3Dv6.0 Code (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A reduced-order model (ROM) is developed for aeroelastic analysis using the CFL3D version 6.0 computational fluid dynamics (CFD) code, recently developed at the NASA Langley Research Center. This latest version of the flow solver includes a deforming mesh capability, a modal structural definition for nonlinear aeroelastic analyses, and a parallelization capability that provides a significant increase in computational efficiency. Flutter results for the AGARD 445.6 Wing computed using CFL3D v6.0 are presented, including discussion of associated computational costs. Modal impulse responses of the unsteady aerodynamic system are then computed using the CFL3Dv6 code and transformed into state-space form. Important numerical issues associated with the computation of the impulse responses are presented. The unsteady aerodynamic state-space ROM is then combined with a state-space model of the structure to create an aeroelastic simulation using the MATLAB/SIMULINK environment. The MATLAB/SIMULINK ROM is used to rapidly compute aeroelastic transients including flutter. The ROM shows excellent agreement with the aeroelastic analyses computed using the CFL3Dv6.0 code directly.
    Keywords: Aerodynamics
    Type: AIAA Paper 2002-1596 , 43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 22, 2002 - Apr 25, 2002; Denver, CO; United States
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  • 6
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    Evaluation of Linear, Inviscid, Viscous, and Reduced-Order Modeling Aeroelastic Solutions of the AGARD 445.6 Wing Using Root Locus Analysis (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Reduced-order modeling (ROM) methods are applied to the CFD-based aeroelastic analysis of the AGARD 445.6 wing in order to gain insight regarding well-known discrepancies between the aeroelastic analyses and the experimental results. The results presented include aeroelastic solutions using the inviscid CAP-TSD code and the FUN3D code (Euler and Navier-Stokes). Full CFD aeroelastic solutions and ROM aeroelastic solutions, computed at several Mach numbers, are presented in the form of root locus plots in order to better reveal the aeroelastic root migrations with increasing dynamic pressure. Important conclusions are drawn from these results including the ability of the linear CAP-TSD code to accurately predict the entire experimental flutter boundary (repeat of analyses performed in the 1980's), that the Euler solutions at supersonic conditions indicate that the third mode is always unstable, and that the FUN3D Navier-Stokes solutions stabilize the unstable third mode seen in the Euler solutions.
    Keywords: Aerodynamics
    Type: AIAA Paper 2014-0496 , NF1676-16636 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference; Jan 13, 2014 - Jan 17, 2014; National Harbor, MD; United States
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  • 7
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    Ongoing Fixed Wing Research within the NASA Langley Aeroelasticity Branch (2015)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The NASA Langley Aeroelasticity Branch is involved in a number of research programs related to fixed wing aeroelasticity and aeroservoelasticity. These ongoing efforts are summarized here, and include aeroelastic tailoring of subsonic transport wing structures, experimental and numerical assessment of truss-braced wing flutter and limit cycle oscillations, and numerical modeling of high speed civil transport configurations. Efforts devoted to verification, validation, and uncertainty quantification of aeroelastic physics in a workshop setting are also discussed. The feasibility of certain future civil transport configurations will depend on the ability to understand and control complex aeroelastic phenomena, a goal that the Aeroelasticity Branch is well-positioned to contribute through these programs.
    Keywords: Aerodynamics
    Type: NF1676L-20156 , AIAA Aviation 2015; Jun 22, 2015 - Jun 26, 2015; Dallas, TX; United States
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  • 8
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    Computational Aeroelastic Analysis of the Semi-Span Super-Sonic Transport (S4T) Wind-Tunnel Model (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A summary of the computational aeroelastic analysis for the Semi-Span Super-Sonic Transport (S4T) wind-tunnel model is presented. A broad range of analysis techniques, including linear, nonlinear and Reduced Order Models (ROMs) were employed in support of a series of aeroelastic (AE) and aeroservoelastic (ASE) wind-tunnel tests conducted in the Transonic Dynamics Tunnel (TDT) at NASA Langley Research Center. This research was performed in support of the ASE element in the Supersonics Program, part of NASA's Fundamental Aeronautics Program. The analysis concentrated on open-loop flutter predictions, which were in good agreement with experimental results. This paper is one in a series that comprise a special S4T technical session, which summarizes the S4T project.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-1556 , NF1676L-13333 , 13th AIAA Gossamer Systems Forum; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States|14th AIAA Non-Deterministic Approaches Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States|53rd Structures, Structural Dynamics, and Materials Conference (SDM); Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States|20th AIAA/ASME/AHS Adaptive Structures Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States
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  • 9
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    An Overview of the Semi-Span Super-Sonic Transport (S4T) Wind-Tunnel Model Program (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A summary of computational and experimental aeroelastic (AE) and aeroservoelastic (ASE) results for the Semi-Span Super-Sonic Transport (S4T) wind-tunnel model is presented. A broad range of analyses and multiple AE and ASE wind-tunnel tests of the S4T wind-tunnel model have been performed in support of the ASE element in the Supersonics Program, part of the NASA Fundamental Aeronautics Program. This paper is intended to be an overview of multiple papers that comprise a special S4T technical session. Along those lines, a brief description of the design and hardware of the S4T wind-tunnel model will be presented. Computational results presented include linear and nonlinear aeroelastic analyses, and rapid aeroelastic analyses using CFD-based reduced-order models (ROMs). A brief survey of some of the experimental results from two open-loop and two closed-loop wind-tunnel tests performed at the NASA Langley Transonic Dynamics Tunnel (TDT) will be presented as well.
    Keywords: Aerodynamics
    Type: AIAA Paper 2012-1552 , NF1676L-13307 , 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 23, 2012 - Apr 26, 2012; Honolulu, HI; United States
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  • 10
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    An Overview of Preliminary Computational and Experimental Results for the Semi-Span Super-Sonic Transport (S4T) Wind-Tunnel Model (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A summary of computational and experimental aeroelastic and aeroservoelastic (ASE) results for the Semi-Span Super-Sonic Transport (S4T) wind-tunnel model is presented. A broad range of analyses and multiple ASE wind-tunnel tests of the S4T have been performed in support of the ASE element in the Supersonics Program, part of NASA's Fundamental Aeronautics Program. The computational results to be presented include linear aeroelastic and ASE analyses, nonlinear aeroelastic analyses using an aeroelastic CFD code, and rapid aeroelastic analyses using CFD-based reduced-order models (ROMs). Experimental results from two closed-loop wind-tunnel tests performed at NASA Langley's Transonic Dynamics Tunnel (TDT) will be presented as well.
    Keywords: Aerodynamics
    Type: IFASD-2011-147 , NF1676L-12736 , International Forum on Aeroelasticity and Structural Dynamics; Jun 26, 2011 - Jun 30, 2011; Paris; France
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