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  • 1
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    A Comparison of Metallic, Composite and Nanocomposite Optimal Transonic Transport Wings (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Current and future composite material technologies have the potential to greatly improve the performance of large transport aircraft. However, the coupling between aerodynamics and structures makes it challenging to design optimal flexible wings, and the transonic flight regime requires high fidelity computational models. We address these challenges by solving a series of high-fidelity aerostructural optimization problems that explore the design space for the wing of a large transport aircraft. We consider three different materials: aluminum, carbon-fiber reinforced composites and an hypothetical composite based on carbon nanotubes. The design variables consist of both aerodynamic shape (including span), structural sizing, and ply angle fractions in the case of composites. Pareto fronts with respect to structural weight and fuel burn are generated. The wing performance in each case is optimized subject to stress and buckling constraints. We found that composite wings consistently resulted in lower fuel burn and lower structural weight, and that the carbon nanotube composite did not yield the increase in performance one would expect from a material with such outstanding properties. This indicates that there might be diminishing returns when it comes to the application of advanced materials to wing design, requiring further investigation.
    Keywords: Aerodynamics; Composite Materials
    Type: NASA/CR-2014-218185 , NF1676L-18512
    Format: application/pdf
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  • 2
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    Aeropropulsive Design Optimization of a Turboelectric Boundary Layer Ingestion Propulsion System (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Boundary Layer Ingestion (BLI) for aircraft applications was first proposed by Apollo Smith and Howard Roberts in a 1947 paper that studied the use of jet intakes embedded in the boundary layer as a means to maintain laminar flow and reduce aircraft drag. While the use of BLI in aviation didn't catch on it was heavily studied and utilized for marine applications. In 1993 interest in BLI applications to aircraft design was renewed when Leyroy Smith published novel work using a boundary layer analysis combined with basic propulsion modeling to show the potential for significant fuel burn reduction. Smith identified the tightly coupled aero-propulsive nature of BLI as a key challenge in the analysis and design of the concept.
    Keywords: Aeronautics (General)
    Type: GRC-E-DAA-TN56385 , AIAA Aviation Forum; Jun 25, 2018 - Jun 29, 2018; Atlanta, Ga; United States
    Format: application/pdf
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  • 3
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    Efficient Near-Field to Mid-Field Sonic Boom Propagation using a High-Order Space Marching Method (2019)
    In:  CASI
    Details
    Publication Date: 2020-01-22
    Description: No abstract available
    Keywords: Aeronautics (General); Acoustics
    Type: ARC-E-DAA-TN70123 , AIAA Aviation 2019 Forum; Jun 17, 2019 - Jun 21, 2019; Dallas, TX; United States
    Format: application/pdf
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  • 4
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    Approach to Modeling Boundary Layer Ingestion Using a Fully Coupled Propulsion-RANS Model (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Although boundary layer ingestion (BLI), or wake ingestion, is commonly applied in marine propulsion applications, it has not yet seen wide-spread adoption in aircraft applications. However, recent studies have predicted that BLI offers a potential for a 10 reduction in aircraft fuel burn, even on a fairly traditional aircraft configuration. This dramatic reduction in fuel burn is achieved via tight integration of the propulsion system and airframe aerodynamics, but actually realizing such large performance gains will require modifying the aircraft design process to account for this integration. Traditionally, in aircraft design, the airframe and the propulsion system are designed separately and then the engine sizing is managed with a rubber-engine approach. This works when the propulsion system is placed in the free-stream air, away from the aerodynamic influence of the airframe, and it is reasonable to assume that small changes to either system won't have a strong impact on the other.
    Keywords: Aeronautics (General); Aerodynamics
    Type: GRC-E-DAA-TN38657 , AIAA SciTech 2017 & Aerospace Sciences Meeting; Jan 09, 2017 - Jan 13, 2017; Grapevine, TX; United States
    Format: application/pdf
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  • 5
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    High-Fidelity Multidisciplinary Design Optimization of Aircraft Configurations (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: To evaluate new airframe technologies we need design tools based on high-fidelity models that consider multidisciplinary interactions early in the design process. The overarching goal of this NRA is to develop tools that enable high-fidelity multidisciplinary design optimization of aircraft configurations, and to apply these tools to the design of high aspect ratio flexible wings. We develop a geometry engine that is capable of quickly generating conventional and unconventional aircraft configurations including the internal structure. This geometry engine features adjoint derivative computation for efficient gradient-based optimization. We also added overset capability to a computational fluid dynamics solver, complete with an adjoint implementation and semiautomatic mesh generation. We also developed an approach to constraining buffet and started the development of an approach for constraining utter. On the applications side, we developed a new common high-fidelity model for aeroelastic studies of high aspect ratio wings. We performed optimal design trade-o s between fuel burn and aircraft weight for metal, conventional composite, and carbon nanotube composite wings. We also assessed a continuous morphing trailing edge technology applied to high aspect ratio wings. This research resulted in the publication of 26 manuscripts so far, and the developed methodologies were used in two other NRAs. 1
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA/CR-2017-219647
    Format: application/pdf
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  • 6
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    Approach to Modeling Boundary Layer Ingestion Using a Fully Coupled Propulsion-RANS Model (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Airframe-propulsion integration concepts that use boundary layer ingestion have the potential to reduce aircraft fuel burn. One concept that has been recently explored is NASA's Starc-ABL aircraft configuration, which offers the potential for 12% mission fuel burn reduction by using a turbo-electric propulsion system with an aft-mounted electrically driven boundary layer ingestion propulsor. This large potential for improved performance motivates a more detailed study of the boundary layer ingestion propulsor design, but to date, analyses of boundary layer ingestion have used uncoupled methods. These methods account for only aerodynamic effects on the propulsion system or propulsion system effects on the aerodynamics, but not both simultaneously. This work presents a new approach for building fully coupled propulsive-aerodynamic models of boundary layer ingestion propulsion systems. A 1D thermodynamic cycle analysis is coupled to a RANS simulation to model the Starc-ABL aft propulsor at a cruise condition and the effects variation in propulsor design on performance are examined. The results indicates that both propulsion and aerodynamic effects contribute equally toward the overall performance and that the fully coupled model yields substantially different results compared to uncoupled. The most significant finding is that boundary layer ingestion, while offering substantial fuel burn savings, introduces throttle dependent aerodynamics effects that need to be accounted for. This work represents a first step toward the multidisciplinary design optimization of boundary layer ingestion propulsion systems.
    Keywords: Aerodynamics
    Type: GRC-E-DAA-TN37844 , AIAA SciTech 2017; Jan 09, 2017 - Jan 13, 2017; Grapevine, TX; United States
    Format: application/pdf
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  • 7
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    Efficient Near-Field to Mid-Field Sonic Boom Propagation Using a High-Order Space Marching Method (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An efficient strategy for propagating sonic boom signatures from a near-field Computational Fluid Dynamics (CFD) solution to the mid-field is presented. The method is based on a high-order accurate finite-difference discretization of the 3D Euler equations on a specially designed curvilinear grid and a single sweep space marching solution algorithm. The new approach leads to more than a factor of two reduction in overall computational resources compared to the current method used to propagate near-field sonic booms to the ground. Accuracy and efficiency of the near-field to mid-field process is demonstrated using a selection of test cases from the AIAA Sonic Boom Prediction Workshops. Azimuthal dependence of nonlinear wave propagation from the near-field to mid-field is analyzed along with its effects on the ground level noise.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: ARC-E-DAA-TN69561 , AIAA Aviation 2019; Jun 17, 2019 - Jun 20, 2019; Dallas, TX; United States
    Format: application/pdf
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