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Aerospace Systems Design Laboratory (ASDL)
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ItemDevelopment of A Certification Module for Early Aircraft Design(Georgia Institute of Technology, 2019-06) Xie, Jiacheng ; Briceno, Simon ; Mavris, Dimitri N. ; Chakraborty, ImonThe airworthiness certification process of civil transportation aircraft is expensive, timeconsuming, and subject to uncertainty. To reduce the cost and time spent on the certification process, this paper proposes an approach to incorporate certification considerations into early design stages using virtual certification techniques. As a proof of concept, this paper focuses on flight performance certification requirements and developed a certification analysis module for aircraft conceptual and early preliminary design based on FAR-25 Subpart B. The module transforms the regulations from textual documents to quantitative constraint functions and ensures the certification constraint check of the design through physics-based analysis. To validate the module, a Small Single-aisle Aircraft testing model is developed and virtually certified by the module. The certification analysis result of the testing model is benchmarked with public domain data.
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ItemFramework to Assess Effects of Structural Flexibility on Dynamic Loads Developed in Maneuvering Aircraft(Georgia Institute of Technology, 2018-06) Sarojini, Darshan ; Duca, Ruxandra ; Solano, Heriberto D. ; Chakraborty, Imon ; Briceno, Simon ; Mavris, Dimitri N.Sizing loads for major aircraft structural components are often experienced during dynamic maneuvers, several of which are described within the Federal Aviation Regulations as part of certification requirements. A simulation and analysis framework that permits such dynamic loads to be assessed earlier in the design process is an advantage for designers and aligned with the trend towards certification by analysis. Such a framework is demonstrated in this paper using the case of a business jet performing a longitudinal checked pitch maneuver. The maneuver is simulated with a six degree-of-freedom MATLAB/Simulink simulation model, using the aircraft aerodynamic characteristics, mass properties, and an adequate level of modeling for the flight control system and pilot control action. The effects of structural flexibility and deformation of the lifting surfaces and fuselage under maneuver loads are modeled by tracking a number of structural degrees-of-freedom for each. The modular nature of the simulation setup facilitates the assessment of multiple maneuvers, analysis of sensitivity to uncertainty, as well as the identification of the impact of structural flexibility through flexible versus rigid maneuver simulations.
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ItemIntegrated Sizing and Optimization of Aircraft and Subsystem Architectures in Early Design(Georgia Institute of Technology, 2018-06) Rajaram, Dushhyanth ; Yu, Cai ; Chakraborty, Imon ; Mavris, Dimitri N.The aerospace industry’s current trend towards novel or More Electric architectures results in some unique challenges for designers due to both the scarcity or absence of historical data and a potentially large combinatorial space of possible architectures. These add to the already existing challenges of attempting to optimize an aircraft design in the presence of multiple possible objective functions while avoiding an overly compartmentalized approach. This paper uses the Integrated Subsystem Sizing and Architecture Assessment Capability to pursue a multi-objective optimization for a large twin-aisle aircraft and a small single-aisle aircraft using the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) algorithm with parallel function evaluations. One novelty of the optimization setup is that it explicitly considers the impacts of subsystem architectures in addition to those of traditional aircraft-level design variables. The optimization yields generations of nondominated designs in which substantially electrified subsystem architectures are found to predominate. As a first assessment of the impact of epistemic uncertainty on the results obtained, the optimization is rerun with altered sensitivities for the thrust-specific fuel consumption penalties due to shaft-power and bleed air extraction. This analysis demonstrated that the composition of architectures on the Pareto frontier is sensitive to the secondary power extraction penalties, but more so for the small single-aisle aircraft than the large twin-aisle aircraft.
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ItemRapid Assessment of Power Requirements and Optimization of Thermal Ice Protection Systems(Georgia Institute of Technology, 2018-06) Bendarkar, Mayank ; Chakraborty, Imon ; Garcia, Elena ; Mavris, Dimitri N.A thermal ice protection system prevents or dispatches ice formed on critical aircraft components like wings or nacelles by heating them either through electro-thermal or pneumatic means. The power requirements for such a system are a function of flight and atmospheric conditions and protected surface area. The developed analysis framework allows evaluation of transient and steady-state cases, anti-icing and de-icing designs, as well as evaporative and running-wet operation. To enable these analyses, a flow solver is first used to calculate local water catch efficiencies and convective heat transfer coefficients on an airfoil. These are then used within a thermal solver which evaluates water and ice accumulations over multiple control volumes under different cases of interest. This control volume approach includes both thermal and mass balances to track temperatures of the protected surface, ice, and water, as well as water/ice layer thicknesses and the water mass flow in or out of the control volume through evaporation or runback. Finally, this tool can yield power requirements for different system layouts and operating conditions, or optimize the protected surface area for a given airfoil under given operating conditions. This can help designers get an estimate of the power draw, and obtain more information on placement of the IPS on novel configurations during the design space exploration phase itself with greater fidelity and minimal computational costs.
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ItemSizing and Optimization of Novel General Aviation Vehicles and Propulsion System Architectures(Georgia Institute of Technology, 2018) Cinar, Gokcin ; Cai, Yu ; Chakraborty, Imon ; Mavris, Dimitri N.The drive for more efficient flying vehicles in all categories may necessitate a significant departure from the tube-and-wing or rotary-wing norms that have been the mainstay of aviation for many decades. This poses challenges for predicting the aerodynamic characteristics and the weight build-up of such unconventional vehicles in early design phases. Additionally, the design and assessment of advanced/unconventional all-electric or hybrid-electric propulsion system architectures require consideration of degrees-of-freedom and trade-offs that do not arise for conventional purely fuel-powered architectures. Thus, there is a need for a flexible vehicle sizing, trade-off, and optimization capability that is not limited to a single vehicle configuration (e.g., fixed-wing, rotary-wing) or propulsion system architecture. To be suitable for the early design phases, such a framework must evaluate relatively quickly, not require extensive definition of the vehicle, and lend itself to customizable design optimization setups. This paper describes the initial creation of such a capability and demonstrates its application to design trade-offs for a General Aviation vehicle with an advanced propulsion system architecture.
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ItemEffects of Epistemic Uncertainty on Empennage Loads During Dynamic Maneuvers(Georgia Institute of Technology, 2018-01) Duca, Ruxandra ; Sarojini, Darshan ; Bloemer, Sebastian ; Chakraborty, Imon ; Briceno, Simon ; Mavris, Dimitri N.The Federal Aviation Regulations contain descriptions of a number of dynamic maneuvers that may lead to the development of critical loads for aircraft structural components. The structural members must be sized and designed to withstand such loads, and this must be demonstrated as part of the certification process. Given the high costs of aircraft certification and the programmatic risk associated with design modifications necessitated during later design stages, there is currently a trend towards certification by analysis. Towards this end, from the structural loads perspective, there is a need for a framework that can simulate maneuvers and evaluate the structural loads thus developed. However, in the earlier phases of design, significant epistemic uncertainty may exist with regard to the aircraft mass properties and aerodynamic characteristics, which in turn lead to uncertainty in the maneuver loads. This work demonstrates a methodology that employs sensitivity and Monte Carlo analyses to assess how maneuvering structural loads are affected by uncertainty factors. These analyses are applied to a dynamic simulation model created to simulate a representative business jet performing a checked pitch maneuver. The resultant variability of critical structural loads provides insight into the areas where epistemic uncertainty should be reduced.
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ItemIntegrated Sizing and Multi-objective Optimization of Aircraft and Subsystem Architectures in Early Design(Georgia Institute of Technology, 2017-06) Rajaram, Dushhyanth ; Cai, Yu ; Chakraborty, Imon ; Puranik, Tejas G. ; Mavris, Dimitri N.The aerospace industry's current trend towards novel or More Electric architectures results in some unique challenges for designers due to both a scarcity or absence of historical data and a potentially large combinatorial space of possible architectures. These add to the already existing challenges of attempting to optimize an aircraft design in the presence of multiple possible objective functions while avoiding an overly compartmentalized approach. This paper uses the Integrated Subsystem Sizing and Architecture Assessment Capability to pursue a multi-objective optimization for a Large Twin-aisle Aircraft and a Small Single-aisle Aircraft using the Non-dominated Sorting Genetic Algorithm II with parallel function evaluations. One novelty of the optimization setup is that it explicitly considers the impacts of subsystem architectures in addition to those of traditional aircraft-level design variables. The optimization yielded generations of non-dominated designs in which substantially electrified subsystem architectures were found to predominate. As a first assessment of the impact of epistemic uncertainty on the results obtained, the optimization was re-run with altered sensitivities for the thrust-specific fuel consumption penalties due to shaft-power and bleed air extraction. This analysis demonstrated that the composition of architectures on the Pareto frontier is sensitive to the secondary power extraction penalties, but more so for the Small Single-aisle Aircraft than the Large Twin-aisle Aircraft.
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ItemA Simulation-Based Framework for Structural Loads Assessment during Dynamic Maneuvers(Georgia Institute of Technology, 2017-06) Goron, Gael ; Duca, Ruxandra ; Sarojini, Darshan ; Shah, Somil R. ; Chakraborty, Imon ; Briceno, Simon ; Mavris, Dimitri N.Federal Aviation Regulations pertaining to structural integrity are key drivers in aircraft design and certification, and often involve critical loads occurring during dynamic maneuvers. In the context of increasing costs of testing and the general trend towards parametric design, there is a need for a more thorough consideration of such dynamic load cases earlier in the design process. In this work, a simulation framework is introduced to assess structural requirements stemming from such dynamic load conditions. Relevant aspects of the dynamics of the aircraft, the control system, and the pilot are modeled in order to simulate the maneuver and thereafter obtain inertial and aerodynamic loads on the empennage during the simulated maneuver. The loads are then translated into structural shear forces and bending moments through structural post-processing routines. This approach is demonstrated for the case of a representative business jet during the checked pitch maneuver. The analyses are repeated for three weight conditions and over the flight envelope for the aircraft from which the load cases resulting in the most constraining loads are determined.
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ItemSubsystem architecture sizing and analysis for aircraft conceptual design(Georgia Institute of Technology, 2015-11-13) Chakraborty, ImonIn traditional aircraft conceptual design, subsystems are largely accounted for implicitly based on available historical data and trends. Such an approach has limitations when novel subsystem architectures such as More Electric or All Electric aircraft are considered, since historical data regarding such architectures is either limited or non-existent. In such cases, the incorporation of more thorough and explicit consideration of the aircraft subsystems into the conceptual design phase is warranted. The first objective of this dissertation is to integrate subsystem sizing and analysis methods that are suitable for the early design phases with the traditional aircraft sizing methodology. The goal is to facilitate the assessment subsystem architecture performance with respect to vehicle and mission level metrics. The second objective is to investigate how the performance of different subsystem architectures varies with aircraft size. The third and final objective is to assess the sensitivity of architecture performance to epistemic and technological uncertainty. These objectives are pursued through the development of an integrated sizing and analysis environment where the subsystems are sized in parallel with the aircraft itself using subsystem models that are computationally inexpensive and do not require detailed aircraft definition. The effects of subsystem mass, secondary power requirements, and drag increments are propagated to the mission performance analysis following which the vehicle and subsystems are re-sized. A number of experiments are performed to first test the capabilities of the developed environment and subsequently assess the performance of numerous subsystem architectures and the sensitivity of select architectures to epistemic and technological uncertainty.