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Browsing by Author "Ricciardi, Anthony Pasquale"

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    Geometrically Nonlinear Aeroelastic Scaling
    Ricciardi, Anthony Pasquale (Virginia Tech, 2014-01-20)
    Aeroelastic scaling methodologies are developed for geometrically nonlinear applications. The new methods are demonstrated by designing an aeroelastically scaled model of a suitably nonlinear full-scale joined-wing aircraft. The best of the methods produce scaled models that closely replicate the target aeroelastic behavior. Internal loads sensitivity studies show that internal loads can be insensitive to axial stiffness, even for globally indeterminate structures. A derived transverse to axial stiffness ratio can be used as an indicator of axial stiffness importance. Two findings of the work extend to geometrically linear applications: new sources of local optima are identified, and modal mass is identified as a scaling parameter. Optimization procedures for addressing the multiple optima and modal mass matching are developed and demonstrated. Where justified, limitations of commercial software are avoided through development of custom tools for structural analysis and sensitivities, aerodynamic analysis, and nonlinear aeroelastic trim.
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    Utility of Quasi-Static Gust Loads Certification Methods for Novel Configurations
    Ricciardi, Anthony Pasquale (Virginia Tech, 2011-09-27)
    Aeroelastic gust and maneuver loads have driven the sizing of primary aircraft structures since the beginning of aviation. Methodologies for determining the gust loads on aircraft have evolved over the last 100 years. There are three general approaches to gust loads analysis: quasi-static, transient, and continuous methods. Quasi-static analysis offers the greatest computational efficiency. A quasi-static formulation referred to as Pratt's Method is the current practice for FAR Part 23 certification requirements. Assumptions made in the derivation of Pratt's Method are acceptable for many conventional aircraft, but additional fidelity from transient and continuous analysis are required to certify FAR Part 25 aircraft. This work provides an assessment of the usability of Pratt's Method for unconventional high altitude long endurance (HALE) aircraft. Derivation Pratt's Method is reviewed and all assumptions are identified. Error of a key curve fit equation is quantified directly. Application dependent errors are quantified by comparing loads calculated using Pratt's Method to loads calculated from transient analysis. To facilitate this effort, a state of the art nonlinear aeroelastic code has been modified to more accurately capture the transient gust response. Application dependent errors are presented in the context of a SensorCraft inspired joined-wing HALE model, and a Helios inspired flying wing HALE model. Recommendations are made on the usability of Pratt's Method for aircraft similar to the two HALE models. It is concluded that Pratt's Method is useful for preliminary design of the joined-wing HALE model, but inadequate for the analysis of the flying wing model. Additional recommendations are made corresponding to subtleties in the implementation of Pratt's Method for unconventional configurations.