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Mavris,
Dimitri N.
Mavris,
Dimitri N.
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ItemDevelopment of a Parametric Drag Polar Approximation for Conceptual Design(Georgia Institute of Technology. School of Aerospace Engineering, 2023-06) Sampaio Felix, Barbara ; Perron, Christian ; Ahuja, Jai ; Mavris, Dimitri N.The present work proposes an efficient parametric approximation of mission drag polars by combining multi-fidelity surrogate models with parametric reduced order modeling techniques. Traditionally, semi-empirical aerodynamic analyses are used to provide drag polars needed for mission analysis during the conceptual design of aircraft. The database needed for these methods is unavailable for unconventional vehicles, and for this reason, many studies rely on higher-fidelity models typical of preliminary design to perform design space exploration for novel vehicle geometries. Due to the high computational cost and evaluation time of these higher-fidelity models, researchers constrain the design space exploration of vehicles by either relying on single discipline optimization or obtaining mission drag polars for a few vehicle geometries within their design loop. The present work demonstrates the application of Hierarchical Kriging surrogate models to obtain mission drag polars for fixed vehicle geometries. Then, the proper orthogonal decomposition reduced order model with Kriging interpolation is used to approximate the coherent structure of mission drag polars. The proposed method is demonstrated on a supersonic commercial aircraft. Experiments showed that both the multi-fidelity surrogate model and the reduced order model are able to emulate vehicle drag polars well for fixed and varying vehicle geometries, respectively.
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ItemCFD Study of an Over-Wing Nacelle Configuration(Georgia Institute of Technology, 2018-10-05) Berguin, Steven H. ; Renganathan, Sudharshan Ashwin ; Ahuja, Jai ; Chen, Mengzhen ; Perron, Christian ; Tai, Jimmy C. M. ; Mavris, Dimitri N.Engine bypass ratio (BPR) has grown significantly over the years, due to a desire for increased efficiency, and the large fan diameters that have resulted are forcing the engines so close to the wing that there is no room left for them to grow any larger due to ground clearance constraints. As BPR increases even further in the future, conventional Under-Wing Nacelle (UWN) installations will therefore no longer be possible without drastic modification of the wing and landing gear. Over-Wing nacelle concepts solve this problem by offering a convenient installation for high BPR turbofans and, additionally, offer the potential to mitigate community noise through engine noise shielding using the wing as a shield. However, OWN has historically warranted concern about unacceptably high drag levels at transonic speeds and the purpose of this research was to determine whether or not drag can be improved enough to take advantage of the aforementioned cross-disciplinary benefits. To do so, three studies were conducted: study 1 conducted a simple nacelle sweep in order to identify and visualize the physical mechanisms driving the configuration, study 2 then conducted a sensitivity analysis in order to understand important design variables and, finally, study 3 performed single point optimization for a trailing edge OWN concept. Overall, results suggests that OWN drag can be improved to levels commensurate with its Under-Wing Nacelle (UWN) counterpart. However, limitations of the analysis tools employed for this research (in the area of shape optimization) were insufficient to outperform the UWN baseline. Such limitations were successfully overcome by modern OWN concepts, such as the Honda Business Jet and the military Lockheed HWB for air mobility missions. Overall, it is therefore the authors' opinion that either leading-edge or trailing-edge mounted OWN configurations are concepts worth investigating further for civil transport applications.
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ItemEconomics of Advanced Thin-Haul Concepts and Operations(Georgia Institute of Technology, 2016) Harish, Anusha ; Perron, Christian ; Bavaro, Daniel ; Ahuja, Jai ; Ozcan, Melek D. ; Justin, Cedric Y. ; Briceno, Simon ; German, Brian J. ; Mavris, Dimitri N.The thin-haul commuter concept refers to an envisioned class of four to nine passenger aircraft operating very short flights and providing scheduled and on-demand air services from smaller airports. Its objective is to enhance regional mobility reach by combining the flexibility of automobile travel with the shorter commute times associated with air travel. To achieve economic viability, the thin-haul commuter concept must provide appreciable economic advantages when compared to current commuter aircraft. This may be achieved by increasing the revenue potential through innovative pricing and scheduling, while drastically reducing operating costs, in particular, energy, maintenance, and labor costs. These ambitious objectives require the infusion of new cutting edge technologies. The use of distributed electric propulsion is investigated to reduce both energy and maintenance expenditures. New avionics systems are considered to enable simplified operations and thus to reduce both labor and training costs. The purpose of this on-going research is to assess the viability of the thin-haul aviation concept by investigating both the operational and economic impact of introducing a fleet of distributed electric propulsion aircraft into the operations of a commuter airline. This paper presents the development of an integrated economics and operations model that incorporates preliminary estimates of a distributed electric propulsion vehicle performance as well as some aspects of typical commuter operator schedules. The model helps compare advanced electric vehicles with more conventional commuters, and therefore enables a preliminary assessment of the expected cost savings.