AE Theses and Dissertations

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Now showing 1 - 5 of 186
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    Numerical methods for modeling compression corners at hypersonic velocities
    (Wichita State University, 2023-12) Sen, Shreya; Hoffmann, Klaus A.
    This study explores hypersonic flow separation, vital for hypersonic space vehicle designs. It is challenging to model shock wave boundary layer interaction (SWBLI) in high-speed gas flow through compression corners. Comparative experiments on various flow models reveal insights into hypersonic chemical non-equilibrium flow. Divergence in shockwave behaviour is influenced by re-circulation zone variations, emphasizing the flow dynamics complexity. Compression corner tests, using the k-omega SST model, elucidate this turbulent boundary layer flow. The successful flow separation which occurs due to the effects of SWBLI interaction is captured. The use of RANS techniques requires advanced models for non-equilibrium turbulent processes, crucial for understanding shock wave boundary layer interactions' effects on pressure and heating loads. This study provides a comprehensive understanding of hypersonic chemical non-equilibrium flow, emphasizing the importance of suitable models, meticulous mesh refinement, and accurate boundary conditions for robust simulations and meaningful comparisons with experimental data.
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    System identification and control of x-plane aircraft
    (Wichita State University, 2023-12) Andress, Christopher; Steck, James E.
    This work introduces two system identification methods and applies them to flight data from the Cessna 172 and LearJet 25 in the X-Plane flight simulator. The identified models are compared to reference models for the two airplanes to evaluate the algorithms application to aircraft. The system identification methods are the Sparse Identification of Nonlinear Dynamics (SINDY) and the Output-Error Method (OEM). Both methods produced linear models that had minimal errors when predicted aircraft states were compared to measured aircraft states. The identified models were then used to develop a control augmentation system for the LearJet in the cruise condition. Desired closed loop dynamics were produced using handling qualities metrics. Implicit model following control was then used to create the control law algorithm that produces the desired closed loop dynamics. Finally, the developed control augmentation system was implemented using MATLAB/Simulink and ran in real time with X-Plane in the loop. The identified models proved to be sufficient to create control law algorithms with excellent performance in the presence of the nonlinear flight simulation.
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    Modelling, sensing, and control design of morphing wing structures
    (Wichita State University, 2023-12) Menon, Alok; Steck, James E.
    This research starts with the development of decentralized, optimal, and adaptive controller design for a Variable Camber Continuous Trailing Edge Flap (VCCTEF) aircraft, the NASA Generic Transport Model (GTM), targeting the goal of minimizing the drag coefficient in cruise condition. To validate and generalize the developed controller design, a novel hybrid partial differential equation (PDE) model representing a flexible wing with rigid and flexible control surfaces was developed. To sense the shape of the flexible wing, the use of a novel sensor developed by NASA, called SansEC, was investigated. In this process, mathematical and artificial neural network (ANN) models of the sensor dynamics was developed with the help of results from experimental test data. It was concluded that the decentralized, optimal, and adaptive controller was successful in achieving the coefficient of drag minimization objective for the VCCTEF aircraft model as well as the hybrid PDE model. The SansEC sensor, with successful modeling, was deemed feasible for use as a sensor on aircraft wings to measure wing deflection. Additional research into the control design for the hybrid PDE model as well as real-world application of SansEC was determined to be necessary due to the limitations and scope of this research.
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    An investigation of the downwash field of aircraft in relation to problems involved in aerial refueling
    (Wichita State University, 1958-06) Holloway, Richard B.; Snyder, Melvin H.
    The purpose of solving the problem presented in this thesis is to provide an approximate method of predicting the downwash effects of a tanker airplane upon a receiver airplane when the two aircraft are flying in formation for the accomplishment of aerial refueling. To the best of the author’s knowledge, this study represents the first attempt at an analytical solution of the problem which is applicable to the general case or any tanker formatting with any receiver. Due to the great many variables involved, any attempt at constructing a generally applicable method implies that certain simplifying assumptions must be made. The results presented in this thesis are, then, probably most useful for obtaining a pre-flight test estimation of downwash effects.
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    An investigation of the core of a curved flow field
    (Wichita State University, 1958-07) Bleicher, Theodor; Razak, Kenneth, 1918-2010
    The purpose of this study was to investigate experimentally the flow of a jet of air over a curved surface. Only the area upstream of the point on the surface, where the flow ceases to follow the curvature, was considered. Along a longitudinal cross section of the jet, measurements were taken and the static pressure distribution, velocity distribution and flow direction were recorded. No close investigation of the boundary layer at the cylindrical surface nor of the mixing zone at the free jet boundaries was made. It was hoped to obtain a criterion as to the "stability" of the jet, i.e. how long the flow follows the· curved surface before breaking away.
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