Aerospace Engineering Commons^™

Comparison Of Theoretical And Multi-Fidelity Optimum Aerostructural Solutions For Wing Design, Jeffrey D. Taylor, Douglas F. Hunsaker

Mechanical and Aerospace Engineering Student Publications and Presentations

As contemporary aerostructural research for aircraft design trends toward high-fidelity computational methods, aerostructural solutions based on theory are often neglected or forgotten. In fact, in many modern aerostructural wing optimization studies, the elliptic lift distribution is used as a benchmark in place of theoretical aerostructural solutions with more appropriate constraints. In this paper, we review several theoretical aerostructural solutions that could be used as benchmark cases for wing design studies, and we compare them to high-fidelity solutions with similar constraints. Solutions are presented for studies with 1) constraints related to the wing integrated bending moment, 2) constraints related to the …

Stabilization Of Energy Level Sets Of Underactuated Mechanical Systems Exploiting Impulsive Braking, Nilay Kant, Ranjan Mukherjee, Hassan Khalil

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Recent investigations of underactuated systems have demonstrated the benefits of control inputs that are impulsive in nature. Here we consider the problem of stabilization of energy level sets of underactuated systems exploiting impulsive braking. We consider systems with one passive degree-of-freedom (DOF) and the energy level set is a manifold where the active coordinates are fixed and the mechanical energy equals some desired value. A control strategy comprised of continuous inputs and intermittent impulsive braking inputs is presented. The generality of the approach is shown through simulation of a three-DOF Tiptoebot; the feasibility of implementation of impulsive control using standard …

Coalescence Characteristics Of Bulk Nanobubbles In Water: A Molecular Dynamics Study Coupled With Theoretical Analysis, Eric Bird, Eric Smith, Zhi Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Coalescence of Two Nanobubbles (NBs) in Water is a Process of Great Importance to Many Industrial Applications. in This Work, We Study the Coalescence of Two Equal-Sized Nitrogen NBs in Water using Molecular Dynamics (MD) Simulations and Continuum-Based Theoretical Analysis. We Vary the NB Diameter from 30 to 50 Nm and Study the Coalescence Characteristics Including the Expansion Speed of the Capillary Bridge between Two Coalescing NBs, the Dynamic Regime of NB Coalescence, the Diameter of Fully Merged NBs, and the Temperature Variation of NBs during the Coalescence Process. for All Cases, We Show the MD Simulation Results Can …

Optimization Of Interplanetary Transfer Trajectories Using The Invariant Manifolds Of Halo Orbits, Ryan Yedinak

Master's Theses

Traditionally, two-body dynamics have been used to design orbital trajectories for interplanetary missions using a series of Lambert’s transfers and gravity assists. Although these are reliable methods, they have extremely high fuel requirements, especially for missions to outer planets. From an orbital mechanics perspective, three ways of reducing fuel requirements for these types of missions are utilizing low energy transfer trajectories, applying low thrust engine parameters, and implementing orbit optimization techniques.

The goal of this thesis is to combine low energy transfers created from the dynamics of the Circular Restricted Three-Body Problem (CRTBP) with low-thrust orbit optimization techniques to develop …

Visual Navigation And Control For Spacecraft Proximity Operations With Unknown Targets, Wyatt J. Harris

Theses and Dissertations

Many current and future spacecraft missions must conduct rendezvous and proximity operations (RPO) with resident space objects (RSOs). An important subset of spacecraft RPO that is yet to be demonstrated on-orbit involves final approach maneuvers with respect to RSOs where no information (such as geometry, inertia, relative velocity, etc.) is known about the target a priori, and no information is actively provided by the target during maneuvering. Such operation with respect to ‘unknown’ targets represents an important possible mission set for Department of Defense spacecraft and is the subject of this research. Two visual servoing frameworks capable of autonomously controlling …

Optimal Incorporation Of Non-Traditional Sensors Into The Space Domain Awareness Architecture, Albert R. Vasso

Theses and Dissertations

The United States Government is the world’s de facto provider of space object cataloging data, but is challenged to maintain pace in an increasingly complex space environment. This work advances a multi-disciplinary approach to better understand and evaluate an underexplored solution recommended by national policy, in which current collection capabilities are augmented with non-traditional sensors. System architecting and literature identify likely needs, performance measures, and contributors to a conceptualized Augmented Network. Multiple hypothetical telescope architectures are modeled and simulated on four separate days throughout the year, then evaluated against performance measures and constraints using optimization. Decision analysis and Pareto optimality …

Application Of Vortex Tubes To Gas Turbine Film Cooling, Matthew N. Fuqua

Theses and Dissertations

To improve thermal efficiency and reduce fuel consumption, gas turbine engines typically operate at increasingly higher turbine inlet temperatures--well in excess of turbine blade material limits--and film cooling schemes are normally employed to reduce metal temperatures within acceptable limits and prevent structural failure. Cooling requirements vary across a blade surface, but there currently exists no means by which coolant temperatures can be locally adjusted to facilitate optimized usage across a blade. Ranque-Hilsch vortex tubes were investigated as a means of adjusting coolant temperatures solely by fluidic means, induced by the phenomenon of temperature separation. Analytical frameworks were developed to determine …

Pseudospectral Methods Of Robust Optimal Motion Planning For Multi-Aperture Space Systems With Motion And Vibration Compensation, Brian W. Bishop

Theses and Dissertations

For multi-body, flexible systems, the ability to achieve rapid reorientation maneuvers can be impacted by nonlinear dynamics and uncertainty in the model parameters impacting the ability to achieve an optimal trajectory computed using nominal parameter values. Trajectory sensitivity to parameter variations increases final pointing error and residual vibrational energy in the system. This manuscript explores using pseudospectral methods to generate robust optimal control trajectories minimizing trajectory sensitivity to parameter variations and derives maneuvers minimizing residual energy and pointing error. The robustness of open-loop optimal control is compared to a standard maneuver derived using traditional methods demonstrating the ability to simultaneously …

Stochastic Satellite Air Drag With The Ballistic Coefficient As A Random Variable, Everett B. Palmer Iv

Theses and Dissertations

The drag acceleration caused by the Earth's atmosphere is a significant cause of prediction uncertainty for low Earth orbit satellites. Most existing research has focused on improving deterministic atmospheric density predictions or on density as a random variable. This research investigates a new paradigm and focuses on modeling the uncertainty caused by air drag using the ballistic coefficient, a component of air drag that is independent of the model used to predict atmospheric density. Time series of ballistic coefficient values were calculated and analyzed as random processes. These random processes were then used as the foundation of a stochastic satellite …

A Real-Time Algorithm To Achieve Precise Coordinated Arrival Times In A Time-Variant Environment, Shawn S. Stephens

Theses and Dissertations

The coordinated arrival time problem seeks to control a vehicle's trajectory to achieve some pre-defined final state at a desired arrival time. The persistent monitoring problem is a type of coordinated arrival problem where a stationary or moving ground target must be constantly observed by a group of aircraft. This research simplifies the problem to overfly the target at specific time intervals relative to the other aircraft in the group while increasing the difficulty of the problem by considering aircraft traveling at vastly different airspeeds. The result of this research is a real time guidance algorithm which accurately guides a …

Evaluation Of Additively Manufactured Lattices Under High Strain Rate Impact, Derek G. Spear

Theses and Dissertations

Several additively manufactured lattice designs and configurations were evaluated under compression loads under various strain rates from quasi-static to highly dynamic. These experiments examined how the mechanical behavior of the lattice changed based on the lattice design properties and the applied strain rates. The modulus of elasticity, yield strength, plateau stress, and toughness were observed to decrease with an increase in strain rate, revealing that the lattice designs exhibit a negative strain rate sensitivity. A new lattice flow stress model was developed to account for the mechanical response of the lattice and was incorporated into a computational model for simulation. …

Blade Optimization For Ground Level Low Speed Wind Turbines, Ryan Foster

Symposium of Student Scholars

Low speed wind turbines can provide inexpensive and clean energy in areas where large scale wind power generation is impractical. The purpose of this research is to explore factors that affect the efficiency of low speed wind turbine blades. The factors that were tested include angle of attack, angle of twist, chord length, average thickness, span, and taper ratio. The goal is to determine a combination of these variables to enable maximum power extraction from a low wind speed source. These blade parameters are optimized for the Southeastern region of the United States. NOAA weather data at ground level are …

Lifting Flow Over A Cylinder As A Lift System, Kyle Mello

Symposium of Student Scholars

The goal of this project is to conceptually design a lift system consisting of rotating cylinders that may improve certain flight characteristics when compared to conventional wings for a typical two passenger airplane. The functions of flaps, ailerons, lift to weight ratio and structural responses are considered. The cylindrical model is developed within CFD simulation software such that it generates the same lift produced by the wings of a Cessna 172 wings at cruising speed. Incompressible flow theoretical solutions are initially shown to compare favorably with the computational predictions for elementary cylindrical designs.

The rotating cylinder aircraft generates the same …

Modeling Dewetting, Demixing, And Thermal Effects In Nanoscale Metal Films, Ryan Howard Allaire

Dissertations

Thin film dynamics, particularly on the nanoscale, is a topic of extensive interest. The process by which thin liquids evolve is far from trivial and can lead to dewetting and drop formation. Understanding this process involves not only resolving the fluid mechanical aspects of the problem, but also requires the coupling of other physical processes, including liquid-solid interactions, thermal transport, and dependence of material parameters on temperature and material composition. The focus of this dissertation is on the mathematical modeling and simulation of nanoscale liquid metal films, which are deposited on thermally conductive substrates, liquefied by laser heating, and subsequently …

Modeling And Design Optimization For Membrane Filters, Yixuan Sun

Dissertations

Membrane filtration is widely used in many applications, ranging from industrial processes to everyday living activities. With growing interest from both industrial and academic sectors in understanding the various types of filtration processes in use, and in improving filter performance, the past few decades have seen significant research activity in this area. Experimental studies can be very valuable, but are expensive and time-consuming, therefore theoretical studies offer potential as a cost-effective and predictive way to improve on current filter designs. In this work, mathematical models, derived from first principles and simplified using asymptotic analysis, are proposed for: (1) pleated membrane …

The Influence Of Trailing Edge Shape And Kinematics On Bio-Inspired Pitching Panels, Justin Thomas King

Dissertations - ALL

Recently, some engineers have turned to the study of swimming and flying animals to provide insight into the design of vehicles that move through air or water. For certain animals swimming in water, thrust is generated primarily by either a caudal fin or fluke located at the posterior end of the swimmer. It has been argued extensively in the existing research literature that biological propulsors of high aspect ration that also display forked, or lunate, planforms are representative of optimized propulsor geometries with respect to propulsive performance. However, recent experimental and computational work on purely pitching panels has demonstrated that …

Flow Interaction Between Turbomachine Blade Row And Flow Resistance Medium, Tong Lin

Dissertations - ALL

This research investigates the fluid-dynamic interaction between close-coupled axial turbomachines and surrounding components, e.g., heat-exchangers, filters, or cooling fins in high-density computer servers, and its effects on turbomachine and system performance. The importance of this research is that the flow interaction effect occurs in every scenario that requires system compactness.

Firstly, a combined experimental and 3-D computational study on an off-the-shelf server cooling fan is performed, showing that the fan performance has little changed. However, the system performance can be very different since the server cooling has a large hub-to-tip radius ratio, which effectively blocks the high resistance media's (HRM) …

Application Of Net-Centric Communications For Disasters (Panel 1: First Responder), Norman Jones

Online Journal of Space Communication

Norman Jones, Transformational Communications Engineering presents: Application of Net-Centric Communications for Disasters

White Paper On Emergency Communications, Space And Advanced Communications Research Institute Space And Advanced Communications Research Institute

Online Journal of Space Communication

Prepared by the Space & Advanced Communications Research Institute (SACRI)

George Washington University

January 5, 2006

Note: This White Paper draws a number of sources including presentations at the National Conference on Emergency Communications (NCEC) held at the George Washington University on December 12-13, 2005. This conference featured some thirty different speakers selected from the federal as well as state and local governments, a wide range of industry spokespeople, several professional societies, relief organizations and NGOs, universities, and other interested parties. There were thirty different sponsors. These presentations, the attendees at this conference and the many sponsors of this event …

Issue 10: From The Guest Editors, Joseph Pelton, Neil Helm

Online Journal of Space Communication

Issue 10 introduction from the guest editors.