This investigation concerns the design, analysis, and initial testing of a new, two-component wall shear gage for 3D, high-temperature flows. This gage is a direct-measuring, non-nulling design with a round head surrounded by a small gap. Two flexure wheels are used to allow small motions of the floating head. Fiber-optic displacement sensors measure how far the polished faces of counterweights on the wheels move in relation to a fixed housing as the primary measurement system. No viscous damping was required. The gage has both fiber-optic instrumentation and strain gages mounted on the flexures for validation of the newer fiber optics. The sensor is constructed of Haynes 230, a high-temperature nickel alloy. The gage housing is made of 316 stainless steel. All components of the gage in pure fiber-optic form can survive to a temperature of 1073 K. The bonding methods of the backup strain gages limit their maximum temperature to 473 K. The dynamic range of the gage is from 0-500 Pa (0-10g) and higher shears can be measured by changing the floating head size. Extensive use of finite element modeling was critical to the design and analysis of the gage. Static structural, modal, and thermal analyses were performed on the flexures using the ANSYS finite element package. Static finite element analysis predicted the response of the flexures to a given load, and static calibrations using a direct force method confirmed these results. Finite element modal analysis results were within 16.4% for the first mode and within 30% for the second mode when compared with the experimentally determined modes. Vibration characteristics of the gage were determined from experimental free vibration data after the gage was subjected to an impulse. Uncertainties in the finished geometry make this level of error acceptable. A transient thermal analysis examined the effects of a very high heat flux on the exposed head of the gage. The 100,000 W/m2 heat flux used in this analysis is typical of a value in a scramjet engine. The gage can survive for 10 minutes and operate for 3 minutes before a 10% loss in flexure stiffness occurs under these conditions. Repeated cold-flow wind tunnel tests at Mach 2.4 with a stagnation pressure from 3.7-8.2 atm (55-120 psia) and ambient stagnation temperature (Re=6.6x107/m) and Mach 4.0 with a stagnation pressure from 10.2-12.2 atm (150-180 psia) and ambient stagnation temperature (Re=7.4x107/m) were performed in the Virginia Tech Supersonic Wind Tunnel. Some of these tests had the gage intentionally misaligned by 25o to create a virtual 3D flow in this nominally 2D facility. Experimental results gave excellent agreement with semi-empirical prediction methods for both the aligned and 25o experiments. This fiber-optic skin friction gage operated successfully without viscous damping. These tests in the supersonic wind tunnel validated this wall shear gage design concept. / Ph. D.

The research was motivated by the desire to use Large Eddy Simulations (LES) to calculate liner heat transfer in industrial scale gas turbine combustors, which operate at high Reynolds numbers and high Swirl numbers. LES has several challenges which need to be surmounted for general application to complex high Reynolds number turbulent flows. The primary challenge in wall bounded flows is the need for very fine grids in the vicinity of walls, which makes LES impractical at high Reynolds numbers. An additional challenge is the accurate representation of inlet turbulent conditions for developing flows such that the computational domain size is limited to the immediate region of interest. The generalization of solutions to surmount these issues in complex geometries and grids is yet another challenge. To meet these challenges, a novel formulation, implementation, and validation of a two layer velocity and temperature zonal wall model along with the implementation of the synthetic eddy method in a generalized coordinate system LES framework is presented in this thesis. The wall model greatly alleviates the grid requirements, whereas the synthetic eddy method provides accurate turbulent inlet boundary conditions. The methods are validated in turbulent channel flow up to a Reynolds number of 2x106, a backward facing step at Re=40,000, before application to a model swirl combustor at Re=20,000 with a Swirl number of 0.43 and flow and heat transfer in an industrial scale can combustor at Re=80,000 and Swirl number of 0.7. The integrated zonal near wall approach for velocity and temperature is then successfully used to investigate flow and heat transfer in a statistically three-dimensional flow of a ribbed duct passage used for the internal cooling of turbine blades. The zonal wall model is further modified to take in to account the effects of surface roughness and successfully used to investigate flow in a rod roughened channel at high Reynolds numbers up to 60,000. In all cases it is shown that the zonal wall model used with the synthetic eddy method for inlet turbulence generation can result in large savings in computational cost without any significant loss in accuracy when compared to wall resolved LES and experiments. In a turbulent channel flow at Re=45,000, computational complexity was reduced by a factor of 285 using wall modeled LES, whereas in a statistically three-dimensional flow and heat transfer in a ribbed duct, at Re=20,000, the computational complexity was reduced by a factor between 60 and 140. In a swirl dominated can combustor at Re=20,000, the reduction was more modest at a factor of 9. / Ph. D.

A retaining wall is subject to various limit states such as sliding, overturning and bearing capacity, and it can fail by anyone of them. Since a great deal of uncertainty is involved in the analysis of the limit states, the use of detenninistic conventional safety factors may produce a misleading result. The main objective of this study is to develop a procedure for the optimum design of a retaining wall by using the reliability theory. Typical gravity retaining walls with four different heights were selected in this study. The walls were designed first to satisfy the conventional design criteria, and later the safety indices inherent in the walls were computed by using Advanced First Order Second Moment method. With the safety indices the probabilities of failure for the three limit states were calculated and the probabilistically optimized design could be achieved by using the probability of failure. The influence of the coefficient of variation on the probability of failure was investigated. The ratios of base width to wall height which lead to the optimum design were obtained through a parametric study. / Ph. D.

In today's society, awash with digital media, the physical book should still be treated as a valuable object. It is a symbol of knowledge and, in the same way that the stones of historic buildings tell the story of their times, the physical book carries the truths of the past to each new generation, not only by the words it contains, but in how it is bound and set and worn. The library rises around the book, offering shelves that may be explored, allowing people to discover as they browse. The neighborhood library serves as an anchor for the community; without physical books, the library is gutted of its essential purpose, becoming merely a community gathering place. Members of the community must be given space to move through the books as they progress from the public realm of the street into the semi-public space of a library reading room, and perhaps beyond to their private places of study. Each stage of their journey should be a clearly defined 'place' with its own purpose and potential. At the same time, the spatial boundaries in this progression must be integrated in order to invite people to move from one to another, to discover the books and the knowledge contained within. My thesis project has explored and developed these theoretical ideas into a library and housing project for Washington, DC's West End neighborhood. / Master of Architecture

A study on the possibilities of place-making by systematically separating the traditional responsibilities of the wall as an architectural element. Walls usually serve several simultaneous structural, enveloping and distributional duties. The project consists in designing a house where four distinct but interacting types of walls are present, each with a well defined duty. Each necessary but deliberately insufficient in itself: one provides the structure; another is a continuous skin for enclosure and partition; still another solely weatherproofs and, finally, one filters the light and grants privacy. The four walls function as layers with the capacity of interplay, while retaining their identity. The places resulting from these boundaries assert their presence and function in view of the character bestowed by the form of their enclosure. The choice of material, assembly, texture and color in unique correspondence to each boundary's usefulness, complete the experience of the inhabitant and architectural form comes about. / Master of Architecture

"A significant work of architecture is never the product of a single individual. It is always a collaboration with history and tradition, with the silent wisdom of the discipline of architecture. An architect who understands the essence of his craft accepts his role as a builder of a tradition, and he places his work in the context of this continuum with combined humility and pride." Juhani Pallasmaa. / Master of Architecture

The first aim of this work was to integrate, validate, and document, a digital particle image quantification (Flow-IQ) software package developed in conjunction with and supported by Aeroprobe Corporation. The system is tailored towards experimental fluid mechanics applications. The second aim of this work was to test the performance of DPIV algorithms in wall shear flows, and to test the performance of several particle sizing algorithms for use in spray sizing and average diameter calculation. Several particle sizing algorithms which assume a circular particle profile were tested with DPIV data on spray atomization, including three point Guassian, four point Gaussian, and least squares algorithms. A novel elliptical diameter estimation scheme was developed which does not limit the measurement to circular patterns. The elliptic estimator developed in this work is able to estimate the diameter of a particle with an elliptic shape, and assumes that the particle is axisymmetric about the x or y axis. Two elliptical schemes, the true and averaged elliptical estimators, were developed and compared to the traditional three point Gaussian diameter estimator using theoretical models. If elliptical particles are theoretically used, the elliptical sizing schemes perform drastically better than the traditional scheme, which is limited to diameter measurements in the x-direction. The error of the traditional method in determining the volume of an elliptical particle increases dramatically with the eccentricity. Monte Carlo Simulations were also used to characterize the error associated with wall shear measurements using DPIV. Couette flow artificial images were generated with various shear rates at the wall. DPIV analysis was performed on these images using PIV algorithms developed by other researchers, including the traditional multigrid method, a dynamically-adaptive DPIV scheme, and a control set with no discrete window offset. The error at the wall was calculated for each data set. The dynamically adaptive scheme was found to estimate the velocity near the wall with less error than the no discrete window offset and traditional multigrid algorithms. The shear rate was found to be the main factor in the error in the velocity measurement. In wall shear velocity measurement, the mean (bias) error was an order of magnitude greater than the RMS (random) error. A least squares scheme was used to correct for this bias error with favorable results. The major contribution of this effort stems from providing a novel elliptical particle sizing scheme for use in DPIV, and quantifies the error associated with wall shear measurements using several DPIV algorithms. A test bed and comprehensive user's manual for Flow-IQ v2.2 was also developed in this work. / Master of Science

This study concerns the design, analysis, and initial testing of a novel skin friction gage for applications in three-dimensional, high-speed, high-enthalpy flows. Design conditions required favorable gage performance in the Arc-Heated Facilities at Arnold Engineering Development Center. Flow conditions are expected to be at Mach 3.4, with convective heat properties of h= 1,500 W/(m°·K) (264 Btu/(hr·ft°·°R)) and T_aw= 3,900 K (7,000 °R). The wall shear stress is expected to be as high as τ_w= 2,750 Pa (0.40 psi) with a correlating coefficient of skin friction value around C_f= 0.0035. Through finite element model and analytical analyses, a generic gage design is predicted to remain fully functional and within reasonable factors of safety for short duration tests. The deflection of the sensing head does not exceed 0.025 mm (0.0001 in). Surfaces exposed to the flow reach a maximum temperatures of 960 K (1,720 °R) and the region near the sensitive electronic components experience a negligible rise in temperature after a one second test run. The gage is a direct-measuring, non-nulling design in a cantilever beam arrangement. The sensing head is flush with the surrounding surface of the wall and is separated by a small gap, approximately 0.127 mm (0.005 in). A dual-axis, semi-conductor strain gage unit measures the strain in the beam resulting from the shear stress experienced by the head due to the flow. The gage design incorporates a unique bellows system as a shroud to contain the oil filling and protect the strain gages. Oil filling provides dynamic and thermal damping while eliminating uniform pressure loading. An active water-cooling system is routed externally around the housing in order to control the temperature of the gage system and electronic components. Each gage is wired in a full-bridge Wheatstone configuration and is calibrated for temperature compensation to minimize temperature effects. Design verification was conducted in the Virginia Tech Hypersonic Tunnel. The gage was tested in well-documented Mach 3.0, cold and hot flow environments. The tunnel provided stagnation temperatures and pressures of up to T₀= 655 K (1,180 °R) and P₀= 1,020 kPa (148 psi) respectively. The local wall temperatures ranged from T_w= 292 to 320 K (525 to 576 °R). The skin friction coefficient measurements were between 0.00118 and 0.00134 with an uncertainty of less than 5%. Results were shown to be repeatable and in good concurrence with analytical predictions. The design concept of the gage proved to be very sound in heated, supersonic flow. When it worked, it did so very effectively. Unfortunately, the implementation of the concept is still not robust enough for routine use. The strain gage units in general were often unstable and proved to be insufficiently reliable. The detailed gage design as built was subject to many potential sources of assembly misalignment and machining tolerances, and was susceptible to pre-loading. Further recommendations are provided for a better implementation of this design concept to make a fully functional gage test ready for Arnold Engineering Development Center. / Master of Science

A wall is a primordial architectural artifact. The power and potential of a wall lies in its ability to transcend the necessities of construction and become a generator of architecture. A wall can be more than a plane in space, it can sculpt light and provide housing for various activities within its tectonic dimension. These additional functions can create an experience of both solidity of a wall as well as the possibility of inhabiting a wall. The creation of a "place". A wall also possesses the ability to create a sense of place. This can occur not only through the provision of habitable space, but also through the provision of bearing points for other structural members, illuminable surfaces, or zones of both visual and physical penetration. Within this thesis project, the wall generates a stair, and together, they begin to produce the rest of the architecture. At first there is a wall. Then there is the apartment. / Master of Architecture

The re-use of any architecture site, whether it is empty or still holding a presence in remaining elements, creates a connection with the past. Formed by a retaining wall and smokestack, an outdoor room is the destination from which two paths direct the inhabitant. This room divides the site and is surrounded by two buildings designed as a library. Through the use of additional architectural elements, frame and column, the inhabitant is guided along the two paths through visual and physical markers. The inhabitant can either move through the building and find framed views of the smokestack and outdoor room, or move around the building, descending the site towards the outdoor room. This project uses a series of perspective drawings to show the designated paths from the street to the outdoor room. / Master of Architecture