Theses

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A Low-Order Aerodynamic Prediction Approach for Fuselage Forces and Wakes.
(2017-08-15) Gupta, Utkarsh Bibhas; Ashok Gopalarathnam, Chair; Kenneth Granlund, Member; Gregory Buckner, Member
A Non-Invasive Technique for Acoustic Resonance Measurement in Supersonic Cavity Flows Using Shadowgraph Imaging and Data Processing.
(2025-05-05) Srivastava, Tushar Eric; Laura Paquin, Chair; Marie Muller, Member; Jack Edwards, Member
Accelerating Reactive Flow Simulations with Deep Operator Networks: Integration of DeepONets with PeleLMeX.
(2025-05-12) Sachdeva, Kunal; Tarek Echekki, Chair; Chi-An Yeh, Member; Srinath Ekkad, Member
Actuation and Control Strategies for Miniature Robotic Surgical Systems
(2002-08-12) Stevens, Jason Michael; Dr. Edward Grant, Committee Member; Dr. Gregory Buckner, Committee Chair; Dr. M.K. Ramasubramanian, Committee Member
Over the past 20 years, tremendous advancements have been made in the fields of minimally invasive surgery (MIS) and minimally invasive robotic assisted (MIRA) surgery. Benefits from MIS include reduced pain and trauma, reduced risks of post-operative complications, shorter recovery times, and more aesthetically pleasing results. MIRA approaches have extended the capabilities of MIS by introducing three-dimensional vision, eliminating tremors, and enabling the precise articulation of smaller instruments. These advancements come with their own drawbacks, however. Robotic systems used in MIRA procedures are large, costly, and do not offer the miniaturized articulation necessary to facilitate tremendous advancements in MIS. This research tests the hypothesis that miniature actuation can overcome some of the limitations of current robotic systems by demonstrating accurate, repeatable control of a small end-effector. A 10X model of a two link surgical manipulator is developed, using antagonistic shape memory alloy (SMA) wires as actuators, to simulate motions of a surgical end-effector. Artificial neural networks (ANNs) are used in conjunction with real-time visual feedback to "learn" the inverse system dynamics and control the manipulator endpoint trajectory. Experimental results are presented for indirect, on-line learning and control. Manipulator tip trajectories are shown to be accurate and repeatable to within 0.5 mm. These results confirm that SMAs can be effective actuators for miniature surgical robotic systems, and that intelligent control can be used to accurately control the trajectory of these systems.
Additively Manufactured Sacrificial Tooling for Carbon Fiber-Reinforced Polymer Composite Fabrication.
(2016-06-23) Lakshman, Narender Shankar; Mark Pankow, Chair; John Strenkowski, Member; Binil Starly, Member
The Aerodynamic Analysis and Aeroelastic Tailoring of a Forward-Swept Wing
(2006-05-08) Roberts, David William; Dr. Kara Peters, Committee Member; Dr. Charles E. Hall, Committee Chair; Dr. James Selgrade, Committee Member
The use of forward-swept wings has aerodynamic benefits at high angles of attack and in supersonic regimes. These consist of reduction in wave drag, profile drag, and increased high angle of attack handling qualities. These increased benefits are often offset due to an increase in structural components, to overcome flutter and wing tip divergence due to high loading of the wing tips at high angles of attack. The use of composite materials and aeroelastic tailoring of the structures eliminates these instabilities without a significant increase in weight. This work presents the design of an aeroelastic wing structure for a highly forward-swept wing, and the verification of the aerodynamic and structural finite element analysis through experimental testing.
Aerodynamic Analysis of a Coaxial Turbine in Yaw for Hydrokinetic Energy Harvesting
(2018-03-27) Nand Kishore Khatri, Dheepak; Kenneth Granlund, Chair; Ashok Gopalarathnam, Member; Matthew Bryant, Member
Aerodynamic Fuselage Design and Engine Integration for the Vampire Light Sport Aircraft.
(2013-03-26) Armes, Robert James; Charles Hall, Chair; James Selgrade, Minor; Ashok Gopalarathnam, Member
Aerodynamic Validation using MER and Phoenix Entry Flight Data.
(2011-02-25) Thomas, Casey; Robert Tolson, Committee Chair; Fred DeJarnette, Committee Member; Lawrence Silverberg, Committee Member
Airfoil Flow Characteristics in a Pure Surge Environment at Constant Incidence.
(2018-07-02) Barrier, Adron Thomas; Kenneth Granlund, Chair; Ashok Gopalarathnam, Member; Matthew Bryant, Member
Airfoil Flow-Separation and Stall Detection Using Surface-Mounted Pitot Tubes.
(2017-08-28) Aleman Chona, Maria Auxiliadora; Ashok Gopalarathnam, Chair; Kenneth Granlund, Member; Matthew Bryant, Member
Algorithmic Enhancements to the VULCAN Navier-Stokes Solver
(2003-08-15) Litton, Daniel; Dr. Jack R. Edwards, Committee Chair; Dr. D. Scott McRae, Committee Member; Dr. Ashok Gopalarathnam, Committee Member
VULCAN (Viscous Upwind aLgorithm for Complex flow ANalysis) is a cell centered, finite volume code used to solve high speed flows related to hypersonic vehicles. Two algorithms are presented for expanding the range of applications of the current Navier-Stokes solver implemented in VULCAN. The first addition is a highly implicit approach that uses subiterations to enhance block to block connectivity between adjacent subdomains. The addition of this scheme allows more efficient solution of viscous flows on highly-stretched meshes. The second algorithm addresses the shortcomings associated with density-based schemes by the addition of a time-derivative preconditioning strategy. High speed, compressible flows are typically solved with density based schemes, which show a high level of degradation in accuracy and convergence at low Mach numbers (M < 0.1). With the addition of preconditioning and associated modifications to the numerical discretization scheme, the eigenvalues will scale with the local velocity, and the above problems will be eliminated. With these additions, VULCAN now has improved convergence behavior for multi-block, highly-stretched meshes and also can accurately solve the Navier-Stokes equations for very low Mach numbers.
Analysis and Modeling Strategies for Subgrid Turbulence-Chemistry Interactions in High-Speed Combustion.
(2023-08-11) Drummond, Paige Makenzie; Jack Edwards, Chair; Tarek Echekki, Member; Hong Luo, Member
Analysis and Parameter Estimation of the Aerodynamic and Handling Qualities of the C-130A Modified With Wing Tip Tanks
(2004-12-02) Phillips, David; Dr. Charles E. Hall Jr., Committee Chair; Dr. Ashok Gopalarathnam, Committee Member; Dr. James Selgrade, Committee Member
This work presents the background, flight testing, and resulting change in the aerodynamic and handling qualities of a C-130A Hercules modified with wing tip tanks. The data collected during the baseline and modified flight tests of this aircraft demonstrated the potential aerodynamic benefits of a tip tank design that incorporates a greater aspect ratio and end plating effects. Wing mounted pressure belts measured a 24% increase in local Cl near the tip tanks. This local increase in lift contributed to a 38% increase in CL max for the airplane. The pressure and dynamic data was gathered using a LIFT (Linux In Flight Testing) system, and it laid the foundation for finding the longitudinal and lateral directional stability coefficients of the airplane. Then using MATLAB® and the System IDentification Programs for AirCraft (SIDPAC) to reduce this data, it was possible to generate aerodynamic, lateral, and longitudinal parameters that clearly proved the overall benefits of the design change. The demonstrated lift benefits of these uniquely designed tip tanks for the C-130A cargo transport proved that by capitalizing on the benefits of a combination tip tank and end plate design it is possible to generate increased lift without adversely affecting the stability and dynamic parameters of the aircraft.
Analysis of Adhesive Bonded Fiber-Reinforced Composite Joints
(2001-07-23) Ficarra, Christina Helene; Dr. Eric Klang, Chair; Dr. J. Eischen, Member; Dr. L. Silverberg, Member
The work presented in this thesis involved the analysis of adhesive bonded joints for composite bridge decks and was divided into three phases. The first phase involved a parametric study on a single lap joint using ANSYS finite element analysis software. The purpose of the parametric study was to alter the geometry and material properties of the joint and study their effects on the stress distribution in both the adherends and adhesive. The four different cases studied included adding a taper to the adherends, different edge shapes on the adhesive layer, a material stiffness imbalance and a geometric stiffness imbalance. It was found that for the taper case and the edge shape case, the stress field in the joint was affected slightly. The material and geometric stiffness imbalance cases had the most drastic affect on the stress field of both the adhesive and adherend. Phase two of this study involved physical tests on single lap joints pulled in uniaxial tension. Tests were performed on three different types of laminates in order to study the interfacial effects these laminates had on the adhesive bond. It was found that by changing the surface of the composite, the mode of failure changed significantly.Phase three of this research involved a study on surface preparation. Three different surface preparations were conducted on the adherends of a butt-strap joint. The first included an acetone wipe. The second involved sanding the adherends. The third surface preparation involved adding APRIME-2, a secondary bonding agent, to the adherends before adding the strap. By simply sanding the adherends, the load to failure was increased by 350% compared to an acetone wipe. The ATPRIME-2 improved the load to failure by an additional 60% as well as improved the failure mode to a fiber tear. It was concluded that surface preparation has a major impact on the behavior of adhesively bonded joints.
Analysis of Taxi Test Data for an Unmanned Aerial VehicleImplemented with Fluidic Flow Control
(2006-07-07) Turner, Drew Patrick; Dr. Sharon Lubkin, Committee Member; Dr. Ashok Gopalarathnam, Committee Member; Dr. Charles E. Hall, Jr., Committee Chair
Serpentine inlet ducts are utilized in many aircraft where the inlet capture area is located off the thrust line or there is a desire to conceal the engine compressor face. Due to the curvature that characterizes a compact serpentine duct, issues with flow distortion and total pressure loss at the engine face arise leading to reduction in propulsion system performance. Computational analysis has shown that flow control implementing micro-fluidic vortex generators significantly reduces the losses. Previous work at North Carolina State University has demonstrated the benefits of a fluidic flow control of this type in a highly compact serpentine inlet duct through the design and experimental static testing of a propulsion system for an uninhabited aerial vehicle. With the implementation of flow control, engine face distortion was reduced and propulsion system performance was increased. This work continues the investigation of the effectiveness of the fluidic flow control by examining the performance of the system during dynamic situations through high speed taxi testing of an uninhabited aerial vehicle implemented with this technology. Additionally, the collected data was used to compare calculated takeoff parameters to values calculated using standard takeoff analysis.
Analytical and Experimental Approaches to Airfoil-Aircraft Design Integration
(2002-06-07) McAvoy, Christopher William; Dr. Kailash C. Misra, Committee Member; Dr. Ndaona Chokani, Committee Member; Dr. Ashok Gopalarathnam, Committee Chair
The aerodynamic characteristics of the wing airfoil are critical to achieving desired aircraft performance. However, even with all of the advances in airfoil and aircraft design, there remains little guidance on how to tailor an airfoil to suit a particular aircraft. Typically a trial-and-error approach is used to select the most-suitable airfoil. An airfoil thus selected is optimized for only a narrow range of flight conditions. Some form of geometry change is needed to adapt the airfoil for other flight conditions and it is desirable to automate this geometry change to avoid an increase in pilot workload. To make progress in these important aeronautical needs, the research described in this thesis is the result of seeking answers to two questions: (1) how does one efficiently tailor an airfoil to suit an aircraft? and (2) how can an airfoil be adapted for a wide range of flight conditions without increased pilot workload? The first part of the thesis presents a two-pronged approach to tailoring an airfoil for an aircraft: (1) an approach in which aircraft performance simulations are used to study the effects of airfoil changes and to guide the airfoil design and (2) an analytical approach to determine expressions that provide guidance in sizing and locating the airfoil low-drag range. The analytical study shows that there is an ideal value for the lift coefficient for the lower corner of the airfoil low-drag range when the airfoil is tailored for aircraft level-flight maximum speed. Likewise there is an ideal value for the lift coefficient for the upper corner of the low-drag range when the airfoil is tailored for maximizing the aircraft range. These ideal locations are functions of the amount of laminar flow on the upper and lower surfaces of the airfoil and also depend on the geometry, drag, and power characteristics of the aircraft. Comparison of the results from the two approaches for a hypothetical general aviation aircraft are presented to validate the expressions derived in the analytical approach. The second part of the thesis examines the use of a small trailing-edge flap, often referred to as a 'cruise flap,' that can be used to extend the low-drag range of a natural-laminar-flow airfoil. Automation of such a cruise flap is likely to result in improved aircraft performance over a large speed range without an increase in the pilot work load. An approach for the automation is presented here using two pressure-based schemes for determining the optimum flap angle for any given airfoil lift coefficient. The schemes use the pressure difference between two pressure sensors on the airfoil surface close to the leading edge. In each of the schemes, for a given lift coefficient this nondimensionalized pressure difference is brought to a predetermined target value by deflecting the flap. It is shown that the drag polar is then shifted to bracket the given lift coefficient. This non-dimensional pressure difference can, therefore, be used to determine and set the optimum flap angle for a specified lift coefficient. The two schemes differ in the method used for the nondimensionalization. The effectiveness of the two schemes are verified using computational and wind-tunnel results for two NASA laminar flow airfoils. To further validate the effectiveness of the two schemes in an automatic flap system, a closed-loop control system is developed and demonstrated for an airfoil in a wind tunnel. The control system uses a continuously-running Newton iteration to adjust the airfoil angle of attack and flap deflection. Finally, the aircraft performance-simulation approach developed in the first part of the thesis is used to analyze the potential aircraft performance benefits of an automatic cruise flap system while addressing trim drag considerations.
An Analytical Method to Evaluate Laminar Convective Heating Rates for Paraboloids with Perfect Gas Chemistry.
(2014-03-06) Desai, Pragnashri Sudhirbhai; Fred DeJarnette, Chair; Ashok Gopalarathnam, Member; Andre Mazzoleni, Member
Antireflection Property of a Periodic Nanocone Structured Solid-Solid Interface.
(2012-05-17) Yang, Qiaoyin; Chih-Hao Chang, Chair; Yong Zhu, Member; Xiaoning Jiang, Member
Bouncing, Sliding and Rolling Dynamics of a Spherical Rover Crossing a Ravine
(2006-12-08) Hartl, Alexandre Emmanuel; DR. ANDRE P. MAZZOLENI, Committee Chair
This study presents a numerical simulation model predicting the motion of a tumbleweed rover as it encounters ravines and valleys. The research provides an understanding of the range of tumbleweed design parameters essential for mobility over varied terrain. The study also introduces a numerical model covering the rover's rolling, sliding and bouncing behaviors and the transitions between these modes of movement. A collision model based on Kane's method of dynamics is used to study the impact between the rover and flat terrain. The model is extended by considering collisions on hills, and a numerical model is created tracking the rover's motion and transition between different terrain types. Rolling and sliding models for a rover in motion are developed for flat and sloping terrains. This study includes several case studies which demonstrate the model's utility as an initial design tool for tumbleweed rovers.

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Browsing Theses by Discipline "Aerospace Engineering"