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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
    Format: text
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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
    Format: application/pdf
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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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    Analysis of V-G Records from the SNB-1 Airplane (1946)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Availability data obtained on SNB-1 trainer-class airplanes were analyzed and results presented as flight envelopes which predict occurrences of large values of air speed and acceleration. Comparison is made with SNJ-4 trainer-class airplane data analyzed by the same method. It is concluded that flight envelopes are satisfactory; that the two types show large differences in flight loads and speeds experience; and that SNB-1 will seldom, if ever, exceed design limit load factor and restricted speed, which SNJ-4 can be expected to exceed design-limit load factor and restricted speed in a very small number of flight hours.
    Keywords: Aerodynamics
    Type: NACA-WR-L-759 , NACA-MR-L6F27a
    Format: application/pdf
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  • 6
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    Flight Tests of the Lateral Control Characteristics of an F6F-3 Airplane Equipped with Spring-Tab Ailerons (1945)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Tests were made to determine whether spring-tab ailerons tended to oscillate or flutter in speed ranges up to 400 mph. Flight tests showed spring-tab ailerons had desirable light stick forces and no tendency to overbalance. No flutter tendencies were indicated up to 400 mph, and any oscillations following abrupt control deflections were heavily damped. Recommendations were made for modifications to increase aileron effectiveness at low speeds without affecting lateral control at high speeds by increasing available deflection and modifying spring-tab arrangement.
    Keywords: Aerodynamics
    Type: NACA-WR-L-149 , NACA-ARR-L5C23
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  • 7
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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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  • 8
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    Hyper-X Research Vehicle (HXRV) Experimental Aerodynamics Test Program Overview (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper provides an overview of the experimental aerodynamics test program to ensure mission success for the autonomous flight of the Hyper-X Research Vehicle (HXRV). The HXRV is a 12-ft long, 2700 lb lifting body technology demonstrator designed to flight demonstrate for the first time a fully airframe integrated scramjet propulsion system. Three flights are currently planned, two at Mach 7 and one at Mach 10, beginning in the fall of 2000. The research vehicles will be boosted to the prescribed scramjet engine test point where they will separate from the booster, stabilize, and initiate engine test. Following 5+ seconds of powered flight and 15 seconds of cow-open tares, the cowl will close and the vehicle will fly a controlled deceleration trajectory which includes numerous control doublets for in-flight aerodynamic parameter identification. This paper reviews the preflight testing activities, wind tunnel models, test rationale, risk reduction activities, and sample results from wind tunnel tests supporting the flight trajectory of the HXRV from hypersonic engine test point through subsonic flight termination.
    Keywords: Aerodynamics
    Type: AIAA Paper 2000-4011 , Applied Aeronautics; Aug 14, 2000 - Aug 17, 2000; Denver, CO; United States
    Format: text
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  • 9
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    Aerodynamic Database Development for the Hyper-X Airframe Integrated Scramjet Propulsion Experiments (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper provides an overview of the activities associated with the aerodynamic database which is being developed in support of NASA's Hyper-X scramjet flight experiments. Three flight tests are planned as part of the Hyper-X program. Each will utilize a small, nonrecoverable research vehicle with an airframe integrated scramjet propulsion engine. The research vehicles will be individually rocket boosted to the scramjet engine test points at Mach 7 and Mach 10. The research vehicles will then separate from the first stage booster vehicle and the scramjet engine test will be conducted prior to the terminal decent phase of the flight. An overview is provided of the activities associated with the development of the Hyper-X aerodynamic database, including wind tunnel test activities and parallel CFD analysis efforts for all phases of the Hyper-X flight tests. A brief summary of the Hyper-X research vehicle aerodynamic characteristics is provided, including the direct and indirect effects of the airframe integrated scramjet propulsion system operation on the basic airframe stability and control characteristics. Brief comments on the planned post flight data analysis efforts are also included.
    Keywords: Aerodynamics
    Type: AIAA Paper 2000-4006 , Applied Aerodynamics; Aug 14, 2000 - Aug 17, 2000; Denver, CO; United States
    Format: application/pdf
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  • 10
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    Hyper-X Research Vehicle (HXRV) Experimental Aerodynamics Test Program Overview (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper provides an overview of the experimental aerodynamics test program to ensure mission success for the autonomous flight of the Hyper-X Research Vehicle (HXRV). The HXRV is a 12-ft long, 2700 lb lifting body technology demonstrator designed to flight demonstrate for the first time a fully airframe integrated scramjet propulsion system. Three flights are currently planned, two at Mach 7 and one at Mach 10, beginning in the fall of 2000. The research vehicles will be boosted to the prescribed scramjet engine test point where they will separate from the booster, stabilize. and initiate engine test. Following 5+ seconds of powered flight and 15 seconds of cowl-open tares, the cowl will close and the vehicle will fly a controlled deceleration trajectory which includes numerous control doublets for in-flight aerodynamic parameter identification. This paper reviews the preflight testing activities, wind tunnel models, test rationale. risk reduction activities, and sample results from wind tunnel tests supporting the flight trajectory of the HXRV from hypersonic engine test point through subsonic flight termination.
    Keywords: Aerodynamics
    Type: AIAA Paper 2000-4011 , 18th Applied Aeronautics Conference; Aug 14, 2000 - Aug 17, 2000; Denver, CO; United States
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