Dissertations

Permanent URI for this collectionhttps://www.lib.ncsu.edu/resolver/1840.20/24

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A New Hybrid LES/RANS Model with Eddy Viscosity Transport (EVT) Based Outer-layer Length Scale.
(2017-08-15) Shen, Minao; Jack Edwards, Chair; Ashok Gopalarathnam, Member; Hong Luo, Member; Carl Kelley, Minor
A p-adaptive Discontinuous Galerkin Method for Single- and Multi-material Hydrodynamics with Load Balancing.
(2023-05-10) Li, Weizhao; Hong Luo, Chair; Jack Edwards, Member; Chi-An Yeh, Member; Zhilin Li, Minor
A Parallel Implicit Reconstructed Discontinuous Galerkin Method for Compressible Turbulent Flows on 3D Hybrid Grids.
(2016-07-08) Liu, Xiaodong; Hong Luo, Chair; Jack Edwards, Member; Hassan Hassan, Member; Zhilin Li, Member
A Parametric Study on the Laser-Forced Ignition of Laminar and Turbulent Round Jets in Non-Ideal Environments.
(2020-03-25) Ley, Kevin Michael; Venkateswaran Narayanaswamy, Chair; Kenneth Granlund, Member; Kevin Lyons, Member; Alexei Saveliev, Member; Phillip Westmoreland, Graduate School Representative
A Robust and Efficient Finite Volume method for Compressible Two-Phase Flows at All Speeds on Unstructured Grids.
(2018-08-13) Pandare, Aditya Kiran; Hong Luo, Chair; Jack Edwards, Member; Pramod Subbareddy, Member; Pierre Gremaud, Member
An Adaptive Grid Algorithm for Air Quality Modeling
(1998-09-29) Srivastava, Ravi K; Dr. D. Scott McRae, Chair; Dr. F. DeJarnette, Member; Dr. Robert White, Member; Dr. M. Talat Odman, Member
The physical and chemical processes responsible for air pollution span a wide range of spatial scales. For example, there may be point sources, such as power plants that are characterized by relatively small spatial scales compared to the size of the region that may be impacted by such sources. To obtain accurate distributions of pollutants in an air quality simulation, the pertinent spatial scales can be resolved by varying the physical grid node spacing.A new dynamic adaptive grid algorithm, the Dynamic Solution Adaptive Grid Algorithm - PPM (DSAGA-PPM), is developed for use in air quality modeling. Given a fixed number of grid nodes, DSAGA-PPM distributes these nodes in response to spatial resolution requirements of the solution field and then updates the solution field based on the resulting distribution of nodes. DSAGA-PPM is implemented dynamically to resolve any evolving solution features. Tests with model problems demonstrate that DSAGA-PPM calculates advection much more accurately than the corresponding static grid algorithm (SGA-PPM) and, therefore, would assure more accurate starting concentrations for chemistry calculations. For example, after one revolution of four rotating cones, 87% of each of the cone peaks is retained using DSAGA-PPM while only 63% is retained using SGA-PPM. The root-mean-square errors in DSAGA-PPM results are about 4-5 times lower than those in the corresponding SGA-PPM results. Tests with reacting species and sources demonstrate that DSAGA-PPM provides the needed solution resolution. In simulations of a rotating and reacting conical puff, the root-mean-square errors in DSAGA-PPM results are about 4-6 times lower than those in the corresponding SGA-PPM results. In simulations of a power plant plume, the DSAGA-PPM solution reflects the early, the intermediate, and the mature stages of plume development; these stages are not seen in the corresponding SGA-PPM solution. Finally, it is demonstrated that DSAGA-PPM provides an accurate description of the ozone production resulting due to dynamic interactions between emissions from two power plants and an urban area. In general, these results reflect that DSAGA-PPM is able to provide accurate spatial and temporal resolution of rapidly changing and complex concentration fields. Performance achieved by DSAGA-PPM in model problem simulations indicates that it can provide accurate air quality modeling solutions at costs 10 times less than those incurred in obtaining equivalent static grid solutions.
Advancements in Aerodynamic Technologies for Airfoils and Wings
(2006-12-08) Jepson, Jeffrey Keith; Dr. Jeffrey A. Joines, Committee Member; Dr. Charles E. Hall, Committee Member; Dr. Hassan A. Hassan, Committee Member; Dr. Ashok Gopalarathnam, Committee Chair
Although aircraft operate over a wide range of ﬂight conditions, current fixed geometry aircraft are optimized for only a few of these conditions. By altering the shape of the aircraft, adaptive aerodynamics can be used to increase the safety and performance of an aircraft by tailoring the aircraft for multiple light conditions. Of the various shape adaptation concepts currently being studied, the use of multiple trailing-edge ﬂaps along the span of a wing offers a relatively high possibility of being incorporated on aircraft in the near future. Multiple trailing-edge ﬂaps allow for effective spanwise camber adaptation with resulting drag beneﬁts over a large speed range and load alleviation at high-g conditions. The research presented in this dissertation focuses on the development of this concept of using trailing-edge ﬂaps to tailor an aircraft for multiple liight conditions. One of the major tasks involved in implementing trailing-edge ﬂaps is in designing the airfoil to incorporate the ﬂap. The ﬁrst part of this dissertation presents a design formulation that incorporates aircraft performance considerations in the inverse design of low-speed laminar-ﬂow adaptive airfoils with trailing-edge cruise ﬂaps. The beneﬁt of using adaptive airfoils is that the size of the low-drag region of the drag polar can be effectively increased without increasing the maximum thickness of the airfoil. Two aircraft performance parameters are considered: level-ﬂight maximum speed and maximum range. It is shown that the lift coefficients for the lower and upper corners of the airfoil low-drag range can be appropriately adjusted to tailor the airfoil for these two aircraft performance parameters. The design problem is posed as a part of a multidimensional Newton iteration in an existing conformal-mapping based inverse design code, PROFOIL. This formulation automatically adjusts the lift coefficients for the corners of the low-drag range for a given ﬂap deﬂection as required for the airfoil-aircraft matching. Examples are presented to illustrate the ﬂapped-airfoil design approach for a general aviation aircraft and the results are validated by comparison with results from post-design aircraft performance computations. Once the airfoil is designed to incorporate a TE ﬂap, it is important to determine the most suitable ﬂap angles along the wing for different flight conditions. The second part of this dissertation presents a method for determining the optimum flap angles to minimize drag based on pressures measured at select locations on the wing. Computational ﬂow simulations using a panel method are used "in the loop" for demonstrating closed-loop control of the ﬂaps. Examples in the paper show that the control algorithm is successful in correctly adapting the wing to achieve the target lift distributions for minimizing induced drag while adjusting the wing angle of attack for operation of the wing in the drag bucket. It is shown that the "sense-and-adapt" approach developed is capable of handling varying and unpredictable inﬂow conditions. Such a capability could be useful in adapting long-span ﬂexible wings that may experience signiﬁcant and unknown atmospheric inﬂow variations along the span. To further develop the "sense-and-adapt" approach, the method was tested experimentally in the third part of the research. The goal of the testing was to see if the same results found computationally can be obtained experimentally. The North Carolina State University subsonic wind tunnel was used for the wind tunnel tests. Results from the testing showed that the "sense-and-adapt" approach has the same performance experimentally as it did computationally. The research presented in this dissertation is a stepping stone towards further development of the concept, which includes modeling the system in the Simulink environment and flight experiments using uninhabited aerial vehicles.
Advancements in Low-Order Modeling of Unsteady Airfoil Flows.
(2024-11-07) Lee, Yi Tsung; Ashok Gopalarathnam, Chair; Jack Edwards, Member; Mohammad Farazmand, Member; Matthew Bryant, Member
Aerothermodynamic Design Sensitivities for a Reacting Gas Flow Solver on an Unstructured Mesh Using a Discrete Adjoint Formulation.
(2017-03-17) Thompson, Kyle Bonner; Hassan Hassan, Co-Chair; Peter Gnoffo, Co-Chair; Jack Edwards, Member; John Griggs, Graduate School Representative; Hong Luo, Member
An Enriched Shell Finite Element for Progressive Damage Simulation in Composite Laminates.
(2016-10-31) McElroy, Mark Wayne; Mark Pankow, Chair; Jeffrey Eischen, Member; T. Kevin O'Brien, Technical Consultant; John Wang, Technical Consultant; Kara Peters, Vice-Chair; Melissa Pasquinelli, Member
An Investigation into Trajectory Control Systems with Applications to High-Altitude Scientific Ballooning.
(2022-03-25) Yoder, Christopher Doolin; Andre Mazzoleni, Chair; Matthew Bryant, Member; Lawrence Silverberg, Member; Subhashish Bhattacharya, Member
An Investigation of the Krypton Laser-Induced Fluorescence Spectral Lineshape for Composition-Independent Thermometry Applied to Combustion Environments.
(2018-11-02) Zelenak, Dominic Charles; Venkateswaran Narayanaswamy, Chair; Kevin Lyons, Member; Chih-Hao Chang, Member; Alexei Saveliev, Member; Igor Bolotnov, Graduate School Representative
Analysis of Aeroheating Augmentation and Control Interference Due to Reaction Control System Jets on Blunt Capsules.
(2010-05-28) Dyakonov, Artem; Fred DeJarnette, Committee Chair; Jack Edwards, Committee Member; David McRae, Committee Member; Hassan Hassan, Committee Member; Pierre Gremaud, Committee Member
Analysis of Hypersonic Aircraft Inlets Using Flow Adaptive Mesh Algorithms
(2001-04-06) Neaves, Michael Dean; Dr. D. Scott McRae, Chair; Dr. H.A. Hassan, Member; Dr. F.R. DeJarnette, Member; Dr. J.R. Edwards, Member; Dr. M.A. Vouk, Member; Dr. J.S. Scroggs, Member
The numerical investigation into the dynamics of unsteady inlet flowfields is applied to a three-dimensional scramjet inlet-isolator-diffuser geometry designed for hypersonic type applications. The Reynolds-Averaged Navier-Stokes equations are integrated in time using a subiterating, time-accurate implicit algorithm. Inviscid fluxes are calculated using the Low Diffusion Flux Splitting Scheme of Edwards. A modified version of the dynamic solution-adaptive point movement algorithm of Benson and McRae is used in a coupled mode to dynamically resolve the features of the flow by enhancing the spatial accuracy of the simulations. The unsteady mesh terms are incorporated into the flow solver via the inviscid fluxes. The dynamic solution-adaptive grid algorithm of Benson and McRae is modified to improve orthogonality at the boundaries to ensure accurate application of boundary conditions and properly resolve turbulent boundary layers. Shock tube simulations are performed to ascertain the effectiveness of the algorithm for unsteady flow situations on fixed and moving grids. Unstarts due to a combustor and freestream angle of attack perturbations are simulated in a three-dimensional inlet-isolator-diffuser configuration.
Analytical and Computational Investigations of Airfoils Undergoing High-Frequency Sinusoidal Pitch and Plunge Motions at Low Reynolds Numbers
(2008-11-10) McGowan, Gregory Zar; Dr. Harvey Charlton, Committee Member; Dr. Jack Edwards, Committee Member; Dr. Hassan Hassan, Committee Member; Dr. Ashok Gopalarathnam, Committee Chair
Current interests in Micro Air Vehicle (MAV)technologies call for the development of aerodynamic-design tools that will aid in the design of more efficient platforms that will also have adequate stability and control for flight in gusty environments. Influenced largely by nature MAVs tend to be very small, have low flight speeds, and utilize flapping motions for propulsion. For these reasons the focus is, specifically, on high-frequency motions at low Reynolds numbers. Toward the goal of developing design tools, it is of interest to explore the use of elementary flow solutions for simple motions such as pitch and plunge oscillations to predict aerodynamic performance for more complex motions. In the early part of this research, a validation effort was undertaken. Computations from the current effort were compared with experiments conducted in a parallel, collaborative effort at the Air Force Research Laboratory (AFRL). A set of pure-pitch and pure-plunge sinusoidal oscillations of the SD7003 airfoil were examined. Phase-averaged measurements using particle image velocimetry in a water tunnel were compared with computations using two flow solvers: i) an incompressible Navier-Stokes Immersed Boundary Method and ii) an unsteady compressible Reynolds-Averaged Navier-Stokes (RANS) solver. The motions were at a reduced frequency of $k = 3.93$, and pitch-angle amplitudes were chosen such that a kinematic equivalence in amplitudes of effective angle of attack (from plunge) was obtained. Plunge cases showed good qualitative agreement between computation and experiment, but in the pitch cases, the wake vorticity in the experiment was substantially different from that predicted by both computations. Further, equivalence between the pure-pitch and pure-plunge motions was not attained through matching effective angle of attack. With the failure of pitch/plunge equivalence using equivalent amplitudes of effective angle of attack, the effort shifted to include pitch-rate and wake-effect terms through the use of analytical methods including quasi-steady thin-airfoil theory (QSTAT) and Theodorsen's theory. These theories were used to develop three analytical approaches for determining pitch motions equivalent to plunge motions. A study of variation in plunge height was then examined and followed by a study of the effect of rotation point using the RANS solver. For the range of plunge heights studied, it was observed that kinematic matching between plunge and pitch using QSTAT gave outstanding similarities in flow field, while the matching performed using Theodorsen's theory gave the best equivalence in lift coefficients for all cases. The variation of rotation point revealed that, for the given plunge height, with rotation point in front of the mid-chord location, all three schemes matched flow-field vorticity well, and with rotation point aft of the mid-chord no scheme matched vorticity fields. However, for all rotation points (except for the mid-chord location), CFD prediction of lift coefficients from the Theodorsen matching scheme matched the lift time histories closely to CFD predictions for pure-pitch. Combined pitch and plunge motions were then examined using kinematic parameters obtained from the three schemes. The results showed that QSTAT nearly cancels the vortices emanating from the trailing edge. Theodorsen's matching approach was successful in generating a lift that was close to constant over the entire cycle. Additionally this approach showed the presence of the reverse Karman vortex sheet through the wake. Combined pitch/plunge motions were then analyzed, computationally and experimentally, with a non-zero mean angle of attack. All computational results compared excellently with experiments, capturing vorticity production on the airfoil's surface and through the wake. Lift coefficient through a cycle was shown to tend toward a constant using Theodorsen's parameters, with the constant being dependent on the initial angle of attack. This result points to the possibility of designing an unsteady motion to match a given flight-condition requirement.
An Application of the Study of Granular Shocks to Aerospace Problems.
(2011-08-03) Padgett, David Alan; Andre Mazzoleni, Chair; Mansoor Haider, Minor; Fred DeJarnette, Member; Gregory Buckner, Member
Artificial Lumbered Flight for Autonomous Soaring.
(2018-11-02) Powers, Thomas Cornelius; Lawrence Silverberg, Co-Chair; Ashok Gopalarathnam, Co-Chair; Scott Ferguson, Member; Edgar Lobaton, Member
Astrodynamics of Spacecraft Under the Influence of the Solar Wind, and Design of Spacecraft Constellations for Solar Storm Early Warning Systems.
(2022-09-28) Gemmer, Thomas Rankin; Andre Mazzoleni, Chair; Lawrence Silverberg, Member; Kevin Lyons, Member; Subhashish Bhattacharya, Member
Autonomous Soaring: The Montague Cross Country Challenge.
(2010-04-23) Edwards, Daniel; Lawrence Silverberg, Committee Chair; Charles Hall, Committee Member; Ashok Gopalarathnam, Committee Member; Mihail Sichitiu, Committee Member
Central Command Architecture for High Order Autonomous Unmanned Systems.
(2014-06-16) Bieber, Chad M; Lawrence Silverberg, Chair; Gregory Buckner, Member; Andre Mazzoleni, Member; Thom Hodgson, Member

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Browsing Dissertations by Discipline "Aerospace Engineering"