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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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ItemSupporting general aviation pilots during rerouting process due to sudden weather changes(Georgia Institute of Technology, 2015-07-24) Tokadli, GulizGeneral aviation pilots need different types of flight information in order to follow events and the changes related to the aircraft environment while flying. However, general aviation cockpits have some limitations as space to install flight displays to provide flight information beyond the basics to the pilot. Additionally, more sophisticated instrumentation is often expensive to install and maintain. With the development of the tablet-based software applications (such as ForeFlight, WingX Pro7 or Garmin Pilot applications for iPad), general aviation pilots have started to use them instead of paper documentation. These software applications provide essential flight information such as weather forecast, aviation charts, flight documents, etc. Unfortunately, the expectations for their capabilities are changing with the increased demand and popularity of these software applications. Therefore, these flight planning software applications are compared to find what is missing and what have not met the expectation of pilots. First, how the software applications support their decision-making process was described and demonstrated to choose the appropriate flight parameters to change flight path while handling with the other cockpit responsibilities. Finally, these design requirements were validated via HITL tests in a part-task flight simulator. The results provided that the suggested design requirements are found highly useful for both novice and expert general aviation pilots. Specifically, novice general aviation pilots might be able to get visualization to compare real-time weather and weather forecast, and then they might gain experience to improve their success for a in-flight re-planning. On the other side, expert pilots might prefer to use this system if they fly an airspace which they are not familiar to weather features of that region.
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ItemIn-cloud ice accretion modeling on wind turbine blades using an extended Messinger model(Georgia Institute of Technology, 2015-05-15) Ali, Muhammad AntthoWind turbines often operate under cold weather conditions where icing may occur. Icing causes the blade sections to stall prematurely reducing the power production at a given wind speed. The unsteady aerodynamic loads associated with icing can accelerate blade structural fatigue and creates safety concerns. In this work, the combined blade element-momentum theory is used to compute the air loads on the baseline rotor blades, prior to icing. At each blade section, a Lagrangian particle trajectory model is used to model the water droplet trajectories and their impact on the blade surface. An extended Messinger model is next used to solve the conservation of mass, momentum, and energy equations in the boundary layer over the surface, and to determine ice accretion rate. Finally, the aerodynamic characteristics of the iced blade sections are estimated using XFOIL, which initiate the next iteration step for the computation of air loads via combined blade element theory. The procedure repeats until a desired exposure time is achieved. The performance degradation is then predicted, based on the aerodynamic characteristics of the final iced blades. The 2-D ice shapes obtained are compared against experimental data at several representative atmospheric conditions with acceptable agreement. The performance of a generic experimental wind turbine rotor exposed to icing climate is simulated to obtain the power loss and identify the critical locations on the blade. The results suggest the outboard of the blade is more prone to ice accumulation causing considerable loss of lift at these sections. Also, the blades operating at a higher pitch are expected to accumulate more ice. The loss in power ranges from 10% to 50% of the rated power for different pitch settings under the same operating conditions.
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ItemCompressor conceptual design optimization(Georgia Institute of Technology, 2015-04-27) Miller, Andrew ScottGas turbine engines are conceptually designed using performance maps that describe the compressor’s effect on the cycle. During the traditional design process, the cycle designer selects a compressor design point based on criteria to meet cycle design point requirements, and performance maps are found or created for off-design analysis that meet this design point selection. Although the maps always have a pedigree to an existing compressor design, oftentimes these maps are scaled to account for design or technology changes. Scaling practices disconnect the maps from the geometry and flow associated with the reference compressor, or the design parameters which are needed for compressor preliminary design. A goal in gas turbine engine research is to bridge this disconnect in order to produce acceptable performance maps that are coupled with compressor design parameters. A new compressor conceptual design and performance prediction method has been developed which will couple performance maps to conceptual design parameters. This method will adapt and combine the key elements of compressor conceptual design with multiple-meanline analysis, allowing for a map of optimal performance that is attached to reasonable design parameters to be defined for cycle design. This method is prompted by the development of multi-fidelity (zooming) analysis capabilities, which allow compressor analysis to be incorporated into cycle analysis. Integrating compressor conceptual design and map generation into cycle analysis will allow for more realistic decisions to be made sooner, which will reduce the time and cost used for design iterations.
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ItemApplying a model-based observer to quantitatively assess spatial disorientation and loss of energy state awareness(Georgia Institute of Technology, 2015-04-27) Bozan, Anil EmilioThis thesis demonstrates how a model-based observer can be applied to estimate the reference pilot expectation that can be achieved with any instrument scanning behavior and established models of vestibular inputs. The MBO, developed by the Georgia Tech Cognitive Engineering Center, is applied here in both simple maneuvers examining spatial disorientation and full Air Traffic Control concepts of operations examining loss of energy state awareness. The computational experiments presented in this thesis examine how different effects (i.e., instrument scan pattern, accuracy of pilot perception of flight display information, and awareness of control surface deflections) can prevent or mitigate the susceptibility to spatial disorientation and loss of energy state awareness, thus setting requirements for intervention and countermeasure designs in terms of the scanning behavior they must foster.
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ItemAeroelastic design of a lightweight distributed electric propulsion aircraft with flutter and strength requirements(Georgia Institute of Technology, 2015-04-24) An, SuiDistributed electric propulsion is a promising technology currently being considered for gen- eral aviation-class aircraft that has the potential to increase range and performance without sacrificing low-speed flight characteristics. However, the high-aspect ratio wings enabled by distributed electric propulsion make these designs more susceptible to adverse aeroe- lastic phenomena. This thesis describes the development of a gradient-based optimization framework for aircraft with distributed electric propulsion using structural and aeroelastic constraints. The governing equations for the coupled aeroelastic system form the basis of the static aeroelastic and flutter analysis. In this work, the Doublet-Lattice method is used to evaluate the aerodynamic forces exerted on the wing surface. In order to consider the impact of propeller-induced flow on aerodynamic loading, a one-way propeller-wing coupling is com- puted by superposition of the propeller induced velocity profile calculated using actuator disk theory and the wing flow field. The structural finite-element analysis is performed using the Toolkit for the Analysis of Composite Structures (TACS). The infinite-plate spline method is used to perform load and displacement transfer between the aerodynamic surface and the structural model. Instead of utilizing a conventional flutter analysis, the Jacobi-Davidson method is used to solve the governing eigenvalue problem without a reduction to the lowest structural modes, facilitating the evaluation of the gradient for design optimization. This framework is applied to different configurations with distributed electric propulsion to minimize structural weight subject to structural and aeroelastic constraints. The effect of flutter constraints, wing aspect ratio, and electric propeller quantity are compared through a series of design optimization studies. The results show that larger aspect ratio wings and more electric motors lead to heavier wings that are more susceptible to flutter. This framework can be used to develop lighter aircraft with distributed electric propulsion configuration that satisfy strength and flutter requirements.
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ItemA methodology for capturing the impacts of bleed flow extraction on compressor performance and operability in engine conceptual design(Georgia Institute of Technology, 2015-04-23) Brooks, Joshua DanielThe commercial aviation industry continually faces the challenge of reducing fuel consumption for the next generation of aircraft. This challenge rests largely on the shoulders of engine design teams, who push the boundaries of the traditional design paradigm in pursuit of more fuel efficient, cost effective, and environmentally clean engines. In order to realize these gains, there is a heightened requirement of accounting for engine system and subsystem level impacts from a wide range of variables, earlier in the design process than ever before. One of these variables, bleed flow extraction, or simply bleed, plays an especially greater role; due to the approach engine designers are taking to combat the current state of fuel efficiency. For this reason, this research examined the current state of bleed handling performed during the engine conceptual design process, questioned its adequacy with regards to properly capturing the impacts of this mechanism, and developed a bleed handling methodology designed to replace the existing method. The traditional method of handling bleed in the engine cycle design stage relies on a variety of engine level impacts stemming from zero dimensional thermodynamic analysis, as well as the utilization of a static performance characterization of the engine compression component, the axial flow compressor. The traditional method operates under the assumption that the introduction of additional bleed to the compressor system has created no additional compressor level impact. The methodology developed in this work challenges this assumption in two parts, first by creating a way to evaluate the compressor level impacts caused by the introduction of bleed, and second by implementing the knowledge gained from this compressor level evaluation into the engine cycle design, where the engine level impacts could be compared to those predicted by the traditional method of bleed handling. The compressor level impacts from the addition of bleed were quantified using a low fidelity, multi-stream, meanline analysis. Here, an innovative approach was developed which cross pollinated existing methods used elsewhere in the analysis environment, to account for the bleed impact in the object oriented modeling environment. Implementation of this approach revealed that the addition of bleed negatively and significantly impacts the compressor level performance and operability. With the completion of the above analyses, this newly acquired capability to quantify, or at least qualify, the compressor level bleed impacts was tied into the engine level cycle analysis. This form of component zooming, allows the user to update the bleed flow rate from a number of locations along the compressor, as well as the compressor variable stator vain orientation, within the existing cycle analysis. Utilization of this ability provided engine level performance and operability analyses which revealed a disparity between the traditional and herein developed bleed handling methodology’s predictions. The found results reveal a need for more stringent handling of bleed during the engine conceptual design than the traditional method provides, and suggests that the developed methodology provides a positive step to the realization of this need.
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ItemTowards multi-scale reacting fluid-structure interaction: micro-scale structural modeling(Georgia Institute of Technology, 2015-04-15) Gallagher, TimothyThe fluid-structure interaction of reacting materials requires computational models capable of resolving the wide range of scales present in both the condensed phase energetic materials and the turbulent reacting gas phase. This effort is focused on the development of a micro-scale structural model designed to simulate heterogeneous energetic materials used for solid propellants and explosives. These two applications require a model that can track moving surfaces as the material burns, handle spontaneous formation of discontinuities such as cracks, model viscoelastic and viscoplastic materials, include finite-rate kinetics, and resolve both micro-scale features and macro-scale trends. Although a large set of computational models is applied to energetic materials, none meet all of these criteria. The Micro-Scale Dynamical Model serves as the basis for this work. The model is extended to add the capabilities required for energetic materials. Heterogeneous solid propellant burning simulations match experimental burn rate data and descriptions of material surface. Simulations of realistic heterogeneous plastic-bound explosives undergoing impact predict the formation of regions of localized heating called hotspots which may lead to detonation in the material. The location and intensity of these hotspots is found to vary with the material properties of the energetic crystal and binder and with the impact velocity. A statistical model of the hotspot peak temperatures for two frequently used energetic crystals indicates a linear relationship between the hotspot intensity and the impact velocity. This statistical model may be used to generate hotspot fields in macro-scale simulations incapable of resolving the micro-scale heating that occurs in heterogeneous explosives.
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ItemConflict resolution in a decentralized air traffic concept of operation(Georgia Institute of Technology, 2015-01-09) Genton, AntoineThe current air traffic concept of operations relies on a centralized process in which ground controllers are responsible for determining conflict-free trajectories. However, with new technologies such as ADS-B and GPS, aircraft could directly interact together to resolve their own conflicts in a decentralized manner. The challenge is to guarantee aircraft separation while converging to reasonably fair resolutions for all aircraft. The difficulty is that aircraft have only limited information about how the other aircraft evaluate the cost of conflict resolutions. Thus, this thesis proposes to frame decentralized conflict resolution using game theory. A collaborative decentralized conflict resolution is developed as a sequential bargaining process between the different aircraft. The goal of each aircraft is to minimize the cost associated with the conflict resolution. However, each aircraft doesn’t know the cost function and performance constraints of the other involved aircraft. In the sequential bargaining process developed, aircraft propose at each step personal trajectories to the other aircraft, corresponding to trajectories they would be ready to fly. Then they compute response trajectories, corresponding to trajectories they would have to fly to avoid the conflict if the personal trajectories were flown. If some response trajectories are cheaper than the offered personal trajectories, an agreement is reached; otherwise compromises have to be made by the aircraft by offering more expensive personal trajectories at the next step. Several pairwise conflict experiments, corresponding to different conflict geometries, were conducted to explore different ways of handling performance constraints and different ways of searching trajectories in the resolution space. Ultimately, the algorithm was demonstrated in a large scale simulation with more than a thousand aircraft flying over the Indianapolis Center, incurring more than five hundred conflicts. The traffic sets were taken from real ETMS data over five hours, to represent ‘real’ conditions. 93% of the conflicts were successfully solved by the bargaining process.