Turbulent flow over a rough surface produces sound that radiates outside the near wall region. This noise source is often at a lower level than the noise created by edges and bluff body flows, but for applications with large surface area to perimeter ratios at low Mach number, this noise source can have considerable levels. In the first part of this dissertation, a detailed study is made of the ability of the Glegg & Devenport (2009) scattering theory to predict roughness noise. To this end, comparisons are made with measurements from cuboidal and hemispherical roughness with roughness Reynolds numbers, hu_Ï /ν, ranging from 24 to 197 and roughness height to boundary layer thickness ratios of 5 to 18. Their theory is shown to work very accurately to predict the noise from surfaces with large roughness Reynolds numbers, but for cases with highly inhomogeneous wall pressure fields, differences grow between estimation and measurement. For these surfaces, the absolute levels were underpredicted but the spectral shape of the measurement was correctly determined indicating that the relationship of the radiated noise with the wavenumber wall pressure spectrum and roughness geometry appears to remain relatively unchanged. In the second part of this dissertation, delay and sum beamforming and least-squares analyses were used to examine roughness noise recorded by a 36-sensor linear microphone array. These methods were employed to estimate the variation of source strengths through short fetches of large hemispherical and cuboidal element roughness. The analyses show that the lead rows of the fetches produced the greatest streamwise and spanwise noise radiation. The least-squares analysis confirmed the presence of streamwise and spanwise aligned dipoles emanating from each roughness element as suggested by the LES of Yang & Wang (2011). The least-squares calculated source strengths show that the streamwise aligned dipole is always stronger than that of the spanwise dipole, but the relative magnitude of the difference varies with frequency. / Ph. D.

i am humbled by the prospect of Architecture. it is not formulaic or linear in thought and action and at times it can be difficult and elusive to define. i believe Architecture exists yet experience has shown that not all building endeavors lead to Architecture. i search for Architecture with a willingness to embrace the unknown, allowing my practice to provide a defined realm into which Architectural questions and propositions can evolve and open new forms of discovery. / Master of Architecture

"Regardless of the differences among their citizens, cities always define their community as against the outside world; a settlement with internal defense walls cannot be called a true community." Community Design and Culture of Cities, by Eduardo Lozano pg 5 Throughout the history of human civilization, no manmade structure has been used to defend territory more than the Wall. Walls have been used to delineate the edges of empires, separate communities, limit migration and provide protection from enemies. As a result, the Wall has become synonymous with imperialism, segregation, racism and isolationism. But what about instances when security outweighs all other concerns? Is there a way to use the wall to maintain defensible space without negatively impacting the greater community? In the case of a military installation located in an urban environment, this is a real issue. Walls which protect the sensitive content within, also serve to divide the community. These necessary physical barriers have the incidental consequence of segregating the servicemembers and government civilians within from the community which they serve. I contend that the thoughtful treatment of these barriers can create a "third place" ripe for interaction between the installation and the surrounding community. By designing retail, educational and cultural spaces along the border, the security of the installation can remain intact while also fostering an active relationship with its surroundings. After all, as Eduardo Lozano states, "a settlement with internal defense walls cannot be called a true community." / Master of Science / “Regardless of the differences among their citizens, cities always define their community as against the outside world; a settlement with internal defense walls cannot be called a true community.” Community Design & Culture of Cities, by Eduardo Lozano pg 5 Throughout the history of human civilization, no manmade structure has been used to defend territory more than the Wall. Walls have been used to delineate the edges of empires, separate communities, limit migration and provide protection from enemies. As a result, the Wall has become synonymous with imperialism, segregation, racism and isolationism. But what about instances when security outweighs all other concerns? Is there a way to use the wall to maintain security without negatively impacting the greater community? In the case of a military installation located in an urban environment, this is a real issue. Walls which protect the sensitive content within, also serve to divide the community. These necessary physical barriers have the incidental consequence of segregating the servicemembers and government civilians within from the community which they serve. I contend that the thoughtful treatment of these barriers can create a “third place” ripe for interaction between the installation and the surrounding community. By designing retail, educational and cultural spaces along the border, the security of the installation can remain intact while also fostering an active relationship with its surroundings. After all, as Eduardo Lozano states, “a settlement with internal defense walls cannot be called a true community.”

This research report presented is an engineering analysis of the damage to the Los Angeles River Floodway System by the 1994 Northridge Earthquake. The scope of this research includes: a study of the damage to two specific sections of the L.A. River Channel, a comparison of damaged and undamaged sections of the floodway channel, an analysis to determine the mechanisms of damage, and a look at dynamic earth pressure theories and their predictive capabilities. / Master of Science

An in vitro arterial flow bioreactor system for the generation of physiological flows in a biological environment was designed, constructed, and characterized. The design was based on models previously used to investigate the response of endothelial cells to shear. The model interfaces a bioreactor with flow elements to compose a flow loop that reproduces arterial flow conditions within the bioreactor. High-resolution (8.6 microns) time-resolved (4 ms) velocity field measurements within the bioreactor were obtained using Particle Image Velocimetry (PIV). Two physiological flows were considered, corresponding to medium human arteries at rest and exercise conditions: first, with an average Reynolds number of 150 and a Womersley parameter of 6.4, and second, with an average Reynolds number of 300 and a Womersley parameter of 9.0. Two cases were considered: first, using a smooth artery section, and second, with a confluent layer of human microvascular endothelial cells grown on the inner surface of the artery section. The instantaneous wall shear stress, time-averaged wall shear stress, and oscillatory shear index were computed from the velocity field measurements and compared for the cases with and without cells. These measurements were used to assess the value of the system for measurement of correlations between fluid dynamics and the response of biological tissue. It was determined that the flow present in such a system is not an accurate reproduction of physiological flow, and that direct measurement of the flow is necessary for accurate quantification of cellular response to fluid parameters. / Master of Science

The origins of this project lie in a desire to understand the relationship that exists between light and architecture. Natural light has always played a role in the evolution of architecture, helping us make countless decisions about the things we build. From their siting to their plan, to the nature of their openings, our buildings have to a great extent been shaped by the sun and the moon. The project became a search for new ways for architecture to express the conscious relationship that needs to exist among light, material, structure, and space. / Master of Architecture

The project offers a design for an addition to a Methodist Church in Newport News, Virginia. The proposal includes a new sanctuary, kitchen, meeting room, and entrance. Axonometric inquiries, detailed sections, and explorations with 3-d models document the structural configuration and the inner sanctuary walls of the addition. In addition to the overall design, further investigations include details for seating design, lighting schemes, and flooring specifications. / Master of Architecture

A large-scale moving end-wall system has been designed and built at the Aerospace and Ocean Engineering Department of Virginia Tech. This system forms part of a low-speed linear compressor cascade wind tunnel, where it is used to simulate the effects of the relative motion between the blade tips and casing upon the flow. Detailed 4-sensor hot wire measurements were made at various locations downstream the cascade. The results are presented in term of mean flow field and turbulence flow field. In order to reveal the effects of moving end wall, the results also compared with the results obtained with stationary end wall. / Master of Science

Compact heat exchangers are usually characterized by a large heat transfer surface per unit of volume. These characteristics are useful when thermal energy between two or more fluids must be exchanged without mixing. Most compact heat exchangers are liquid-to-air heat exchangers, with approximately 85% of the total thermal resistance occurring on the air side of the heat exchanger. To reduce the space and weight of a compact heat exchanger, augmentation strategies must be proposed to reduce the air side resistance. However, before any strategies to augment the air side heat transfer can be proposed, a thorough insight of the current mechanisms that govern air side heat transfer is required. The tube wall heat transfer results presented in this paper were obtained both experimentally and computationally for a typical compact heat exchanger design. Both isothermal and constant heat flux tube walls were studied. For the experimental investigation, a scaled-up model of the louvered fin-tube wall was tested in a flow facility. Although computational results for the isothermal tube wall are shown, control of the experimental isothermal tube wall proved to be unrealistic and only heat transfer measurements along the constant heat flux tube wall were made. For the constant heat flux tube wall, reasonable agreement has been achieved between the measurements and the steady, three-dimensional computational predictions. The results of the study showed that high heat transfer coefficients existed at the entrance to the louver array as well as in the louver reversal region. Vortices created at the leading edge of the louvers augmented heat transfer by thinning the tube wall boundary layer. Results indicate that an augmentation ratio of up to 3 times can occur for a tube wall of a louvered fin compact heat exchanger as compared to a flat plate. / Master of Science

Corn silage is one of the major components in dairy cattle rations in the United States. Many factors affect the nutritional composition of corn for silage, such as cropping system, including cover crops, and the composition of the corn plant cell wall. The objectives of the first study were to determine the nutritional quality of different winter crops for silage and to determine the impact of the various winter crops on the succeeding productivity of corn and sorghum. Experimental plots were planted with 15 different winter crop treatments: 5 winter annual grasses in monoculture or with one of two winter annual legumes (crimson clover [CC] and hairy vetch [HV]). After harvesting the winter crops, each plot was planted with either corn or forage sorghum. Crimson clover increased DM yield compared to monocultures but HV did not. Adding legumes increased the crude protein concentration, but reduced the fiber and sugar concentrations of the forages. Even though in vitro neutral detergent fiber digestibility was reduced with the addition of legumes, the concentration of highly digestible non-fibrous components is greater in the mixtures than the monocultures, increasing the nutritive value of the silage. The objective of the second study was to determine the cell wall (CW) composition along the corn stalk. Three phytomers of corn plants were examined: center (C) of ear insertion, upper (U) and lower (L) phytomers. Each phytomer was cut into 4 sections: top (T), middle (M), bottom (B), and node (N). The CW, uronic acid (UA), glucose (GLU), and lignin concentrations did not change among phytomers. The concentrations of arabinose (ARA) and xylose (XYL) were greater in the U than in the L phytomers. Concentrations of CW, ARA, and XYL increased from B to T within the phytomer, but UA and GLU concentrations decreased from B to T. Lignin did not change within the phytomer. In mature corn for silage, changes within the corn internode may be more useful in determining how the environment changes the CW. / Ph. D. / Corn silage is one of the major components in dairy cattle rations in the United States. Many factors can affect the nutritional composition and digestibility of corn for silage, including the crops planted before the corn and the maturity of the corn. I first explored the nutritional quality and potential of different winter crops for use as silage and how these various winter crops impacted the succeeding productivity of corn and sorghum. We used 15 different winter crop treatments: 5 winter annual grasses in monoculture or mixed with one of two winter annual legumes (crimson clover and hairy vetch). After harvesting the winter crops, corn and forage sorghum were planted. The addition of legumes increased winter crop yield compared to monocultures. Adding legumes increased the protein concentration, but reduced the reduced the fiber and sugar concentrations of the winter crops. Fiber digestibility was reduced with the addition of legumes. The type of grass and legume did not change the nutrient composition of the corn and sorghum. I then explored how the cell wall (CW) composition changes along the corn stalk. Corn plants are split up into phytomers. Each phytomer contains a leaf, a section of the stalk called an internode, and a node (connects internodes). Phytomers at the top of the corn plant are less mature than ones at the bottom, and maturity increases from bottom to top within a corn internode. Three phytomers of individual corn plants were each cut into 4 sections: top, middle, bottom, and node. In plants, the primary cell wall is deposited first. The primary cell wall contains cellulose, hemicellulose, and pectin. The secondary cell wall is deposited after growth. The secondary cell wall is composed of cellulose, hemicellulose, and lignin. Corn that is harvested for cows to eat is usually at a late stage of maturity. Therefore, in our study we saw very few differences among phytomers as cellulose, hemicellulose, pectin, and lignin had most likely been fully deposited. However, within the corn internode, we did see variability in the corn plant cell wall. The cell wall concentration overall increased with maturity within the corn internode. Further, arabinose and xylose concentrations (sugars from hemicellulose) also incased with maturity. Hemicellulose is important in connecting the rest of the cell wall to lignin later in maturity. The concentration of uronic acids from pectin and glucose from cellulose decreased with maturity because these are typically deposited first within the plat cells and then level off once lignin is deposited. In mature corn for silage, changes within the corn internode may be more useful in determining how the environment changes the CW.