The purpose of this research was to demonstrate the viability of a method, due to Professor W. R. Sears, for obtaining wind-tunnel wall-corrections from measurements of near-field flow parameters by an interative procedure. A case is made for the improved accuracy of this method over the standard method of images. The wall-correction method was applied to an actual wind-tunnel test of a slightly oversized wing model at low subsonic speeds (Mach number ≈ 0.1). The wind tunnel facility and experimental setup and method are described and discussed. The wall-correction method consists of iterating between the region of space exterior to the test section boundary and the one interior to it. The flow fields in both regions are defined in terms of plane singularity elements each with an unknown, constant strength distribution. The method for expressing these flow fields as a linear system and for obtaining the associated matrices is described. The boundary conditions for the inner flow are slightly different from those of the outer flow because of the presence of the wing. There are actually two different but consistent sets of boundary conditions at the wing which lead to two different but compatible calculations for the wall-correction. The near-field flow parameter measured during the wind-tunnel test is the wing perturbation velocity potential, obtained from the quantity p ͚ - pᵢ. Here, i represents any of the 46 static taps distributed over the test section walls. It was decided to use 140 singularity elements for the outer flow description; therefore, a method was devised for fitting a least-squares surface to the measured p̂ᵢ's and integrating to obtain 140φᵢ's. The procedure for the iterations is described and the criterion for convergence to unconfined flow is presented. Test cases consisting of known, simple flows are used along the way to verify the computational methods. Finally, the wall correction to the lift curve of the wing model is presented as well as the correction at a typical tail position and the correction to the induced drag of the wing.

Thesis is submitted in partial fulfilment of the requirements for the degree of Master of Science in Engineering to the Faculty of Engineering and the Built Environment, School of Mining Engineering, University of the Witwatersrand, Johannesburg, 2017 / Boring of shafts and tunnels in hard rock mines is more prevalent in recent years in South Africa. This normally takes place under substantial stress conditions, where fracturing of rock occurs around the boundaries and ahead of advancing faces of excavations. Fracturing can have a significant impact on boring activities, in some instances causing sidewall spalling which can be extensive, with machine grippers unable to reach the sidewalls. In brittle rock, these fractures are commonly extensional in nature. This research has been undertaken to predict the initiation of extension fractures and their orientations ahead of machine driven tunnels. Furthermore, it will help to assess the stability of the excavations, by evaluating the potential for slab/plate failures. This was based on the typical in situ stress fields for underground deep level mines. The numerical analyses involved the generation of different plots:  Principal stress contour plots, depicting stress distributions around and ahead of tunnel excavation, using cutting planes;  Isosurfaces, showing zones of extension or potential extents of fracturing, applying the extension strain criterion; and  Trajectory ribbons, to demonstrate the orientations of fractures. Based on the results of the stress analyses, potential slab or plate formation was determined. It was noted that the fracture zone is a function of a tunnel size. For instance, a four-metre diameter tunnel is less likely to give boring problems than an eight-metre diameter tunnel. The failure of the tunnels was predicted by employing slab analysis methods. An eight-metre diameter tunnel had slenderness ratio as low as 22.3 as compared with a four-metre diameter tunnel with a slenderness ratio of 27. Looking at buckling stress versus slenderness ratio, this translates to buckling stress values of above 100 MPa for an eight-metre tunnel and to values just below 50 MPa for a four-metre tunnel. The outcome of the research gives a clear indication that boring activities could be undertaken under severe conditions. This could be detrimental to the cutter head, since large slabs and blocks could be encountered during boring. The results of this research can be beneficial in the evaluation of boring conditions prior to and during boring activities. / MT2018

Underground tunnels are considered to be a vital infrastructure component in most cities around the world. Careful planning is always necessary to ensure minimum impact on nearby surface and subsurface structures. This thesis describes the experimental and numerical investigations carried out at McGill University to examine the effect of existing pile foundation on the stresses developing in a newly constructed tunnel supported by a flexible lining system. A small scale testing facility was designed and built to simulate the process of tunnel excavation and lining installation in the close vicinity of pre-installed piles. Lining stresses were measured for different separation distances between the tunnel and the existing piles. Significant decrease in circumferential stresses was observed when the lining was installed at a distance that ranges between one to three times the tunnel diameter from the piles. Two-dimensional finite element analyses were also conducted to investigate the different aspects of the pile-soil-lining interaction including lining deformation, axial forces and bending moments. The measured lining stresses agreed with those obtained using finite element analysis. The results presented in this study provided an insight into understanding an important aspect of this soil-structure interaction problem.

Due to the increased scrutiny of construction costs for infrastructure projects by the public and legislators, it is becoming increasing important for project developers to prepare accurate conceptual cost estimates for transportation tunnel projects at the feasibility stage to aid in making investment decisions. Past studies have emphasized that tunnel-project costs have been significantly underestimated, and cost uncertainties and risks have been identified as the cause of cost under or overestimation. A broad understanding of the factors that contribute to cost underestimation is important as it enables researchers and estimators to develop appropriate functions, evaluate, and implement them to produce realistic cost estimates. This study was aimed at developing parametric cost estimation functions and quantifying their risks for transportation tunnel projects. A comprehensive background study of more than 39 published articles on transportation tunnel infrastructure projects was conducted through a systematic literature review and 40 key estimating parameters that may impact project costs and the associated project logistics were identified. Data from completed tunnel projects were collected and used to develop the parametric cost equations. Exploratory analyses were first performed to discover the correlations among tunnel costs and tunnel cost parameters/drivers. The purpose of this effort was to assess if a relationship existed between tunnel variables and tunnel project cost estimates. Parametric cost estimation functions were then developed for different tunnel applications. There has been no comprehensive study performed to date to develop parametric cost estimation functions that incorporated risk and uncertainty for transportation tunnel projects. Two representative sample case studies were performed and Monte Carlo simulation was used to quantify the associated risks. The results from the case studies illustrate the need to use appropriate techniques to simulate tunnel costs and quantify the risks associated with the estimates. The findings of the study provide a methodology to estimate the costs of transportation tunnels and quantify the uncertainties and risks associated with the costs. The methodology developed in this research could help reduce the incidence of project cost underestimation and alleviate some of the controversies surrounding cost overruns in transportation tunnel projects.

No description available.

A wind tunnel was designed and built to produce a pulsating flow. The pulsation was achieved by a series of shutters (rotating with constant angular velocity) placed upstream of the settling chamber inlet. The system was optimized to obtain nearly sinusoidal velocity waveforms with the highest obtainable amplitudes over the frequency range of 3.4 to 31.3 Hz. The velocity and pressure waveforms are given for different shutters settings and conditions. It was found that the velocity waveform shape and amplitude, obtained in the test section, are a strong function of pressure build-up in the diffuser upstream of the shutters box. An explanation is given, for various shutters settings and conditions, of how pressure release is achieved and how the pressure waveforms are generated. / M.S.

Thesis (MEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Segmentally lined tunnels are increasingly being built to transfer water from one water scheme to another. The segments that line such tunnels are often in the form of pre-cast concrete sections, which are placed around the perimeter of the tunnel. As these tunnels are very expensive to construct, it is imperative that their hydraulic capacities can be calculated accurately. Even a slight variation in the design diameter has a significant effect on the cost of the tunnel. Due to the construction method involved, alternative segments are not always properly aligned. This creates roughness elements in the tunnel commonly known as steps. These steps occur randomly and vary in size. Since the steps lead to increased roughness and thus decrease the hydraulic capacity of the tunnel, it is essential that this effect be allowed for in the design of the tunnel. A hydraulic model was used to determine the contribution of steps to the hydraulic roughness, according to step size and frequency of steps. / AFRIKAANSE OPSOMMING: Tonnels word al hoe meer gebou om water tussen waterskemas te vervoer. Die voering van sulke tunnels word dikwels saamgestel uit voorafvervaardigde beton panele wat geplaas word om 'n huls langs die omtrek van die tonnel te vorm. Aangesien hierdie tonnels geweldig duur is om te bou, is dit uiters noodsaaklik dat die hidrouliese kapasiteit van 'n tonnel akkuraat bereken kan word. 'n Klein variasie in die diameter van die tonnel het 'n betekenisvolle effek op die koste daarvan. Die konstruksiemetode van sulke tonnels veroorsaak dat opeenvolgende panele nie altyd presies oplyn nie. Sulke afwykings in die belyning van die tonnelpanele veroorsaak klein trappies, wat bydra tot die ruheid in die tonne I en sodoende die kapasiteit daarvan laat afneem. Die afwykings varieer in grootte en kom in geen spesifieke patroon voor nie. 'n Modelstudie is uitgevoer om die bydrae wat die afwykings in the belyning van die opeenvolgende ringe tot die hidrouliese weerstand maak, te bepaal.

No description available.

The design of a cascade wind tunnel for testing of compressor blades at high angle of attack is described. Methods to insure uniform velocity profiles and control of inlet turbulence are discussed. The problem of maintaining two-dimensional flows at high angle of attack was addressed. A tunnel capable of testing cascades of compressor blades at angles of attack up to seventy-five degrees was constructed. Performance of the tunnel was evaluated and data were acquired for flow over double-circular-arc blades with angles of attack extending into the fully-stalled region. Comparisons were made with available data in the installed flow regime. Results showed that the tunnel had adequately uniform inlet velocities and low turbulence levels, and that two-dimensional flow was maintained over the center two-thirds of the high-aspect ratio blades. / Master of Science

M.S.