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Doctor of Philosophy with a Major in Aerospace Engineering
Doctor of Philosophy with a Major in Aerospace Engineering
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ItemDevelopment of a Sonic Sensor for Aircraft Applications(Georgia Institute of Technology, 2021-12-14) Carroll, Jonathan D.The field of aeroacoustics has been an area of constant research over the past six decades. Acoustic waves have some special characteristics that allow for heating, cooling, and even active flow control over airfoil shapes using synthetic jets and other methods. They can also be used to measure properties of the flow over an aircraft, including the free-stream pressure ratio, density ratio, and total temperature. The current measurement techniques to obtain these parameters applied to aircraft require a specific probe. It is desired to apply knowledge of acoustics to develop an aircraft sensor that can measure multiple flow properties with minimal impact to the flow field. Adding a sensor that can read total temperature, static temperature, airspeed, and angle of attack will have the added benefit of reducing the number of sensors sticking into the flow and may result in a reduction in failure mode analysis due to the minimization of the number of sensors on the aircraft. This work explores the applicability of sonic anemometry to aircraft for high subsonic and sonic speeds. A computational simulation is developed as a validation of the concept and low speed experiments are shown to validate the theory. This effort identifies the underlying issues associated with applying sonic anemometry to high-speed flows and provides methods to overcome them. This work investigates the use of phased array technology to increase the accuracy and applicability at the higher speeds and smaller footprints (lighter and fewer systems). Phased arrays use the constructive and destructive interference to boost and direct the desired signal, in this case, acoustic waves. These acoustic waves have been shown to provide haptic feedback and levitate small particles utilizing a relatively inexpensive ultrasonic phased array system. It is shown that the ultrasonic phased array overcomes the hydrodynamic noise to produce a strong signal for use in the calculation of the flow parameters up to the maximum speed tested. It is also shown that the signal is strong enough to produce consistent time delay estimations, via cross-correlation, with a 0.05 second sample time to integrate into modern air data systems.
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ItemApplication of Extended Messinger Model for Ice Accretion on Complex Geometries(Georgia Institute of Technology, 2021-10-11) Gupta, AvaniIce accretion can significantly degrade the performance, stability, availability, and affordability of an airborne vehicle. It is imperative that this phenomenon be modeled accurately. While ice accretion studies have been performed on airplane wings, propellers, and helicopter blades, there are very few attempts to model the process on more complex geometries such as fuselages. In this study, an existing in-house Extended Messinger methodology is generalized for complex geometries by modeling the flow field and water droplet transport on unstructured grids, and carrying out the ice accretion calculations along surface streamlines. A general framework has been developed, allowing the use of two-dimensional and three-dimensional, structured, and unstructured, public domain and commercial CFD analyses. The methodology is primarily spilt into three steps: the continuum flow field analysis, the dispersed water phase computations, and the ice accretion module. In the present study, in-house methodologies as well as commercial solvers such as STAR-CCM+ and ANSYS Fluent have been used for the flow field and droplet dispersed phase computations. The in-house methodologies for the dispersed water droplet transport are done using an Eulerian approach, with a one-way interaction between the air flow and the dispersed phase via the drag force exerted on the droplets by the air flow. The ice accretion is carried out along surface streamlines, or optionally along two-dimensional section cuts, using an in-house icing methodology based on the Extended-Messinger model. The predictions from the present approach are compared to available experimental data, and predictions using other solvers such as LEWICE and STAR-CCM+. Several configurations with varying levels of complexity are modeled. These include 2-D airfoils, swept wings, and helicopter fuselage configurations. Time and space sensitivity studies have been done.
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ItemA PHYSICS-BASED MODEL FOR INFLOW CHARACTERISTICS OF MULTI-ROTOR CONFIGURATIONS(Georgia Institute of Technology, 2021-08-13) Chen, Po-WeiA physics-based model for modeling helicopter and autonomous rotor configurations, previously developed for isolated rotors and coaxial rotors in hover and forward flight, has been extended to more general multi-rotor configurations. Simulations for coaxial and tandem rotor configurations have been performed for a number of low and high Reynolds number configurations, and comparisons with test data have been made. The physics behind the rotor interactions has been explored through visualization and analysis of vortex wake structure and inflow velocity distributions. As part of this effort, a fast off-body velocity field analysis that employs GPU processors has been implemented. In addition to computation of inflow velocity field above or below the rotor disks, this approach is capable of rapidly computing and visualizing velocity field on any user specified plane. In many helicopter design studies, the adverse interactions caused by the main rotor wake should be considered in the placement of horizontal and vertical stabilizers, as well as the tail rotors and pusher-propulsors. This capability for rapid calculation and visualization of the off-body flow field would greatly aid the designers in the placement of these components. A previously developed algebraic transition model that regulates the magnitude of the production term in the Spalart-Allmaras one-equation turbulence model has been independently implemented in the present solver. In the present work, this model has been also validated for large scale rotors in hover.
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ItemA Unified Approach for Modeling Fluid-Structure Interactions of Large-Scale Offshore Wind Turbines(Georgia Institute of Technology, 2021-07-26) Pichitkul, AuraluckWind turbine technology has grown over the past several decades and has been globally accepted as an economically viable form of renewable energy. Further development in size and power production of wind turbine demands continuous advances in the underlying technologies - aerodynamics, structures, engineering materials, aeroelasticity, electrical systems, mechanical and hydraulic control, and manufacturing. In this study, focus is placed on two aspects of these technologies – aerodynamics and structures – with the primary goal of economically and accurately predicting the power production of very large-scale flexible wind turbines. To fulfill the first objective, a loose-coupling technique relying on an in-house hybrid CFD solver, and an in-house Euler-Bernoulli CSD solver is developed and used in investigating aeroelastic behavior of a large-scale offshore wind turbine. A 5 MW wind turbine system developed by National Renewable Energy Laboratory (NREL) is analyzed. The aerodynamic loads predicted by GT-Hybrid and the elastic deformations computed by the CFD solver are exchanged using file I/O. The study shows that the NREL 5 MW rotor undergoes significant bending deformations, especially at rated wind speeds. The loss of performance, in terms of power production, should be accounted while performing analyses. To satisfy the second objective of exploring alternative design for large-scale offshore wind turbines, a biplane rotor concept proposed by Wirz, et. al. at the University of California Los Angeles is explored. The study shows that that biplane rotors, with a reduced chord, are effective in producing power comparable to conventional wind turbines at rated condition with considerable mass and cost savings.