Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7462. Adviser: Mark J. Kushner. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4624. Adviser: Rodney Burton. Includes bibliographical references (leaves 89-93) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7463. Adviser: Scott R. White. Includes bibliographical references (leaves 133-138). Available on microfilm from Pro Quest Information and Learning.

Thèse (M.Sc.A.)--Université de Sherbrooke (Canada), 2008. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thesis (Ph.D.)--Drexel University, 2010. / Includes abstract and vita. Includes bibliographical references (leaves 108-117).

Thesis (Ph. D.)--Syracuse University, 2005. / "Publication number AAT 3177030."

<p> It is estimated that the rotor hub of a helicopter is responsible for up to 30% of the parasite drag of a helicopter. This is because the hub is a group of rotating bluff-body shapes exposed to high-velocity flow, which may produce hub revolution-dependent flow structures in the hub wake. These structures also interact with a helicopter&rsquo;s empennage and tail rotor, negatively impacting stability and performance. While some specific helicopter hubs have been studied, no study of a generalized hub shape has taken place. Because the hubs that have been studies are very geometrically complex, computational prediction of hub flow physics is not yet mature enough to be of use to industry. The objective of this study is to characterize the long-age wake of a geometrically simple configuration of canonical bluff bodies to model a helicopter hub. Three scale models were examined, each with four larger arms to represent rotor blade shanks and two smaller arms to represent scissor links. The models were identical in dimension, but one had a smoother arm profile and another had a variation in phase angle between the two sets of arms. The models were mounted in the Experimental Flow Physics Laboratory Large Water Tunnel, and tested at a hub diameter-based Reynolds number of 7.6 &times; 10⁵. Time-resolved velocity measurements were taken 14 hub radii downstream of one model, while phase-averaged velocity measurements were taken 7 hub radii downstream of the other two. Similar trends to previous works were observed, including two-per-hub revolution, four-per-hub revolution, and 6-per-hub revolution frequency content in the velocity spectra. This study therefore aids in the uncovering of fundamental flow physics of rotor hubs, creating a baseline case to which further parametric variations may be compared.</p><p>

<p> Flow separation is a common fluid dynamics phenomenon that occurs within supersonic nozzles while operating at off-design pressures. Typically, off-design pressures result in a shock formation that leads to a non-uniformity of the exiting flow and creates flow separation and flow recirculation. So far, no effective solution has been presented to eliminate flow separation and increase the total performance of the nozzle. The purpose of this work is to investigate whether a Gurney flap may beneficially affect the exiting flow pattern. For a better understanding of the Gurney flap effect, this investigation used a supersonic nozzle geometry based on a previous study by Lechevalier (2005). Results from the tested cases showed a poor effect of the flap at high free-stream Mach number and lower pressure ratio. Simulations of different flap heights along with different parameters showed a slight increase of thrust.</p><p>

<p> Given the increasing complexity of systems and the cost associated with test and evaluation of aerospace systems, more efficient methods are sought. Randomized test designs for aviation developmental test activities and other complex systems may not enable safe test conduct and may be prohibitively costly from a financial or time point of view. This research reviews Design of Experiments (DoE) test design approaches applicable to aerospace prototype test and evaluation activities. It proposes the use of Split Plot Optimal Designs to leverage advantages of DoE while satisfying requirements for limited randomization of the test runs. Through the use of case studies, the Split Plot Optimal Design approach is demonstrated to provide a 58% cost and schedule savings versus a One Factor At a Time approach, and 53% savings from the fully randomized Central Composite Design, while maintaining relevant statistical power. Through the use of Monte Carlo data simulation, the designs are evaluated for application to linear and quadratic models, with statistically significant results measured by Chi Squared and Kolmogorov-Smirnov tests. </p><p>

<p> Applications of sealant and adhesive technologies in aerospace industries require appropriate and reliable sealing materials and tools to provide suitable sealing. Due to a growing use of integral fuel tanks, which utilize the aircraft structure for fuel containment, this study focuses on nozzle geometry optimization of aircraft fuel tank sealant in order to develop and facilitate sealant approval process and to ensure the implementation of suitable fuel tank sealing. </p><p> Computational Fluid Dynamics (CFD) analyses were performed to study the sealant flow characterization and behavior using Star-CCM+ software. An empirical model was developed by the aid of Design of Experiments (DOE) techniques in order to develop a reliable mathematical model based on the collected data from numerical results. Scanning Electron Microscopy (SEM) was utilized to investigate the fracture/deformation of hollow glass microballoons and entrapped air bubbles within the cured sealant. </p><p> The results of this research concluded that the bent in nozzle geometry increases the sealant pressure drop throughout the nozzle. There is an optimized value for travel distance and cross sectional dimension and geometrical shape within the nozzle geometry that minimizes overall dynamic viscosity of the sealant.</p><p>