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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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ItemInvestigation of Physics-Based Approaches for Wind Turbine Modeling and Design(Georgia Institute of Technology, 2009-05-04) Nucci, MichaelRising oil costs have created a need for a new sustainable energy source. Currently wind energy is beginning to fulfill this need. With many financial incentives being offered for clean energy, wind turbines are a promising green energy source. Wind turbine analysis can be difficult and costly. Accurate spanwise pressure distributions are difficult to measure experimentally, and a full-fledged Navier-Stokes analysis is very computationally expensive. A comparison of two separate computer codes was performed. These include PROPID, which uses a blade element momentum theory method and empirical data about the wind turbine airfoil. The second method is a Reynolds Averaged Navier-Stokes (RANS) CFD code called windrotor2 which also was used to predict the performance of the NREL Phase VI rotor. Once the codes were validated they were then used to predict the performance of new rotor designs. This research shows that PROPID can be used as a surrogate model for turbine analysis and design. PROPID can be shown to predict performance that is on par with CFD methods in terms of accuracy, but takes only a fraction of the time to perform the analysis. PROPID can also be shown to accurately predict the performance of new turbine configurations as long as empirical data is readily available.
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ItemInvestigation of Adjoint Based Shape Optimization Techniques in NASCART-GT using Automatic Reverse Differentiation(Georgia Institute of Technology, 2009-05-04) Verma, SiddharthaAutomated shape optimization involves making suitable modifications to a geometry that can lead to significant improvements in aerodynamic performance. Currently available mid-fdelity Aerodynamic Optimizers cannot be utilized in the late stages of the design process for performing minor, but consequential, tweaks in geometry. Automated shape optimization involves making suitable modifications to a geometry that can lead to significant improvements in aerodynamic performance. Currently available mid-fidelity Aerodynamic Optimizers cannot be utilized in the late stages of the design process for performing minor, but consequential, tweaks in geometry. High-fidelity shape optimization techniques are explored which, even though computationally demanding, are invaluable since they can account for realistic effects like turbulence and viscocity. The high computational costs associated with the optimization have been avoided by using an indirect optimization approach, which was used to dcouple the effect of the flow field variables on the gradients involved. The main challenge while performing the optimization was to maintain low sensitivity to the number of input design variables. This necessitated the use of Reverse Automatic differentiation tools to generate the gradient. All efforts have been made to keep computational costs to a minimum, thereby enabling hi-fidelity optimization to be used even in the initial design stages. A preliminary roadmap has been laid out for an initial implementation of optimization algorithms using the adjoint approach, into the high fidelity CFD code NASCART-GT.High-fidelity shape optimization techniques are explored which, even though computationally demanding, are invaluable since they can account for realistic effects like turbulence and viscocity. The high computational costs associated with the optimization have been avoided by using an indirect optimization approach, which was used to dcouple the effect of the flow field variables on the gradients involved. The main challenge while performing the optimization was to maintain low sensitivity to the number of input design variables. This necessitated the use of Reverse Automatic differentiation tools to generate the gradient. All efforts have been made to keep computational costs to a minimum, thereby enabling hi-fidelity optimization to be used even in the initial design stages. A preliminary roadmap has been laid out for an initial implementation of optimization algorithms using the adjoint approach, into the high fidelity CFD code NASCART-GT.
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ItemImage Analysis of Acoustically Excited Bluff Body Flames(Georgia Institute of Technology, 2007-12-17) Plaks, Dmitriy VitalThis thesis analyzes the effects of various bluff bodies on the downstream flow field. Bluff bodies, for example, those typically found in jet engine augmentors, are objects designed to impede the flow in order to stabilize a flame. The effects of different bluff body shapes (cylindrical and triangular), size (6.35 mm, 9.53 mm, 12.7 mm, and 19.1 mm) and heat release are examined with respect to their influence on downstream vorticity strength, vortex separation distance, and vorticity divergence angle. Particle Image Velocimetry (PIV) is used to obtain the velocity field data from which the vorticity field is calculated. The mean flow velocity, U∞ is 2.7 m/s, and the flow is acoustically excited at 300 Hz with a normalized acoustic velocity of u'/U∞ = 0.8. The vorticity divergence angle increases with increasing bluff body size, is not affected by bluff body shape, and has a non-linear correlation with heat release. Downstream vorticity strength is affected by all three parameters (bluff body shape, size and heat release) in a non-linear manner. Vortex separation distance is a function primarily of bluff body size, increasing for larger bodies; however, the separation distance decreases with increasing heat release. Bluff body shape also has an effect on vortex separation distance as the cylindrical bluff body creates a larger separation distance between vortices.
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ItemNon-Deterministic Design of Utility Scale Wind Energy Systems(Georgia Institute of Technology, 2007-05) Scott, RobertThe wind is an increasingly significant source of energy with the rising price of non-renewable fuels. The purpose of this project is to determine the specific intensity and frequency of wind speed required to sustain a large-scale wind farm with power output on the order of hundreds of megawatts. To this end, a non-deterministic methodology will be developed to analyze the viability of wind energy systems. A deterministic analysis method considers the majority of design parameters to be known or fixed and may only perform trade studies on a few parameters at a time to optimize performance. In the case of the energy market though, this is not an advantageous strategy since several factors related to economic viability such as energy prices, interest rates, government incentives, acquisition costs and maintenance are highly variable and cannot be assumed to be known. A non-deterministic, statistical approach to wind turbine design has the advantage of predicting with corresponding levels of certainty the power output and economic viability of an energy system. The primary goal of this project is to define the envelope of operating conditions for a large-scale wind project while considering variables of both engineering and economic significance. The National Renewable Energy Laboratory’s (NREL) Hybrid Optimization Model for Electric Renewables (HOMER) will be incorporated into the previous analysis using YawDyn and PROPID to determine the economic returns on investment in hypothetical financing cases. Cost factors will now be assigned a mean value along with a probability distribution. Monte Carlo simulations will be run for a large number of variations in the assumed economic and engineering variables to develop an accurate estimate of the price per kilowatt-hour of energy produced from the simulated wind project for a variety of site conditions with the goal of finding the most suitable environment for sustainable wind development.
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ItemDirect Conversion for Space Solar Power(Georgia Institute of Technology, 2007-05) Boechler, Nicholas SebastianSpace Solar Power (SSP) is a powerful yet nearly untapped resource with revolutionary potential. SSP systems currently have several roadblocks to their implementation. With the technology in use today, converting solar power to useable energy is inefficient, the required converters have a large mass per unit power, and launching those converters is expensive. More fundamentally, in all current SSP systems, energy is generated in the form of a direct current before being converted again into whatever form is necessary. In addition to the large mass per unit energy of this conversion equipment, such conversion involves significant efficiency losses, further resulting in the prohibitive cost of launching these converters into space. If techniques could be discovered for converting broadband sunlight directly to a useable narrowband application dependent frequency, many fundamental breakthroughs in aerospace endeavors can be achieved. This project studied a large number of options that might lead to direct conversion. Those technology options were analyzed according to which would warrant further exploration from the point of view of aerospace systems applications and possible power per unit mass. Based on these technologies, several advanced concepts were considered. It is also important to make an estimate of the possible power per unit mass that could be achieved with each concept, so that architecture developers can proceed with the development of applications enabled by direct conversion technology. Accordingly, estimates of the possible power per unit mass of potential direct conversion systems were made, and future applications that would benefit from those direct conversion systems were identified. Three possible concepts were developed. These concepts include: a shocked photonic crystal system; a solar pumped maser based on naturally occurring astronomical masers; and an optical antenna array with central signal processing. The optical antenna array and the solar pumped maser were estimated to have a specific power approximately 15.0 and 10.8 times greater, respectively, than conventional photovoltaic systems. Additionally, several applications were identified that would benefit from direct conversion systems, including a SSP grid and electric propulsion.