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Aerospace Systems Design Laboratory (ASDL)
Aerospace Systems Design Laboratory (ASDL)
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ItemA Multi-Fidelity Approximation of the Active Subspace Method for Surrogate Models with High-Dimensional Inputs(Georgia Institute of Technology, 2022-06) Mufti, Bilal ; Chen, Mengzhen ; Perron, Christian ; Mavris, Dimitri N.Modern design problems routinely involve high-dimensional inputs and the active subspace has been recognized as a potential solution to this issue. However, the computational cost for collecting training data with high-fidelity simulations can be prohibitively expensive. This paper presents a multi-fidelity strategy where low-fidelity simulations are leveraged to extract an approximation of the high-fidelity active subspace. Both gradient-based and gradient-free active subspace methods are incorporated with the proposed multi-fidelity strategy and are compared with the equivalent single-fidelity method. To demonstrate the effectiveness of our proposed multi-fidelity strategy, the aerodynamic analysis of an airfoil and a wing are used to define two application problems. The effectiveness of the current approach is evaluated based on its prediction accuracy and training cost improvement. Results show that using a low-fidelity analysis to approximate the active subspace of high-fidelity data is a viable solution and can provide substantial computational savings, yet this is counterbalanced with slightly worse prediction accuracy.
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ItemIntegrated Sizing and Optimization of HybridWing Body Aircraft in Conceptual Design(Georgia Institute of Technology, 2019-06) Xie, Jiacheng ; Cai, Yu ; Chen, Mengzhen ; Mavris, Dimitri N.The hybrid wing body (HWB) configuration is a paradigm shift in commercial transport aircraft design in terms of environmentally responsible characteristics and significant performance improvements over the conventional tube-and-wing configuration. However, the sizing methods and analysis tools used in conceptual design of tube-and-wing aircraft are not fully compatible with HWB due to the highly integrated fuselage and wing. This paper proposes a novel approach to perform parametric sizing and optimization of HWB aircraft at the conceptual design phase, and develops an interdisciplinary design framework which integrates preliminary aerodynamic analysis, weight estimation, propulsion system sizing, and mission analysis. Enabled by the techniques of Design of Experiments and surrogate modeling, a design space exploration is conducted over the top-level aircraft design variables, including sensitivity assessment, feasible design space identification, and constrained multi-objective optimization. The impact of uncertainties in disciplinary analyses and novel technologies on aircraft-level performance is investigated through an uncertainty analysis.
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ItemMulti-UAV Trajectory Optimization Utilizing a NURBS-Based Terrain Model for an Aerial Imaging Mission(Georgia Institute of Technology, 2019-05) Choi, Youngjun ; Chen, Mengzhen ; Choi, Younghoon ; Briceno, Simon ; Mavris, Dimitri N.Trajectory optimization precisely scanning an irregular terrain is a challenging problem since the trajectory optimizer needs to handle complex geometry topology, vehicle performance, and a sensor specification. To address these problems, this paper introduces a novel framework of a multi-UAV trajectory optimization method for an aerial imaging mission in an irregular terrain environment. The proposed framework consists of terrain modeling and multi-UAV trajectory optimization. The terrain modeling process employs a Non-Uniform Rational B-Spline (NURBS) surface fitting method based on point cloud information resulting from an airborne LiDAR sensor or other sensor systems. The NURBS-based surface model represents a computationally efficient terrain topology. In the trajectory optimization method, the framework introduces a multi-UAV vehicle routing problem enabling UAV to scan an entire area of interest, and obtains feasible trajectories based on given vehicle performance characteristics, and sensor specifications, and the approximated terrain model. The proposed multi-UAV trajectory optimization algorithm is tested by representative numerical simulations in a realistic aerial imaging environment, namely, San Diego and Death Valley, California.
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ItemSensitivity Analysis of Aero-Propulsive Coupling for Over-Wing-Nacelle Concepts(Georgia Institute of Technology, 2018) Berguin, Steven H. ; Renganathan, Sudharshan Ashwin ; Ahuja, Jai ; Chen, Mengzhen ; Tai, Jimmy C. M. ; Mavris, Dimitri N.A sensitivity analysis is performed to quantify the relative impact of perturbing a set of design variables representing an airplane configuration with Over-Wing Nacelles (OWN), operating at transonic cruise. The goal is to study the impact of perturbing the engine's XYZ position and power setting on installation drag, engine inlet pressure recovery, and lift curve characteristics. High- fidelity Reynolds Averaged Navier-Stokes (RANS) simulations of the Common Research Model (CRM) modified with powered, over-wing nacelles are performed and dominant main effects and interactions are identified. The most dominant effect was by far the engine's X position, but it was also found that podded OWN configurations exhibit statistically significant, aero-propulsive coupling. Specifically, certain engine locations cause changes in the flow-field that deteriorate inlet pressure recovery and, vice versa, a change in engine boundary conditions can affect installation drag. It is therefore recommended to simulate OWN concepts using a coupled MDA or MDAO approach to capture interdependencies between aerodynamics and propulsion.