D. Phil. / Conventional internal wind tunnel balances are designed and constructed to accommodate foil strain gauges which measure the deformation (strain) of the material. Foil strain gauge balances are known to be affected by electromagnetic interference and temperature. These balances are expensive and their manufacture is time consuming. With an increasing demand for higher accuracy, stiffness, increased resolution and temperature compensation, current balance designs are becoming inadequate. To overcome identified balance deficiencies a research programme in the application of optical Bragg gratings to wind tunnel balances was initiated. In this programme a new concept of using optical fibre Bragg grating sensors, with the advantage of using mechanical amplification to increase sensitivity, and the implementation of temperature compensation techniques was demonstrated on a simulated two component balance.

No description available.

In dense cities, the interactions between all structures, from tall skyscrapers to complex underground tunnel systems, need to be carefully analysed as soon as a new project is considered. This is necessary because of the stress changes in the soil induced by each new construction. Demolishing a building could cause heave at the base of the excavation, deflections in supporting structures and settlements of the surroundings. The behaviour can be modelled in order to predict how large the deformations will be. This thesis investigates the effectiveness of such models. This is done through the application of a parameter sensitivity analysis on models created in Plaxis. The purpose of the analysis is to identify which factors cause discrepancies between the models and the actual displacements monitored on site. The project being examined is located in central London. The analysis focuses on the displacements of existing tunnels below the site caused by the demolition of two buildings. An analysis was carried out to investigate the significance of different parameters, of different material models and methods of analysis, of 3D effects and of inaccurate groundwater data. Ground investigations, laboratory tests and published data were the main sources used to collect reliable initial input parameters for the material models. A model was created in Plaxis 2D using the Mohr-Coulomb and the Hardening Soil with small-strain stiffness material models, using two types of undrained analysis. A model using the Mohr-Coulomb material model was created in Plaxis 3D as well. A sensitivity analysis was then carried out on the 2D models to identify which input parameters were most significant to the tunnel displacements. The results were compared to monitoring data and a back-analysis was carried out to produce more accurate results. The initial and adjusted input parameters were also tested on the 3D model. Finally, the groundwater level was altered. The results indicate that soil stiffness and effective cohesion are the most significant. Small-strain stiffness is shown to be especially important when analysing small tunnel deformation. The 3D model generally yielded more accurate results than the 2D model, while the groundwater level did not appear to affect the deformations. / I tätbebyggda städer bör samspelet mellan olika konstruktioner, från skyskrapor till tunnelsystem, analyseras noga så fort ett nytt projekt ska påbörjas. Detta är kritiskt på grund av den förändrade spänningsfördelning som uppstår i marken vid varje ny byggnation. Marken häver sig, stödmurar deformeras och den omkringliggande marken sätter sig när en byggnad rivs. Denna process kan modelleras för att uppskatta hur stora deformationerna kommer att bli. Det här examensarbetet utvärderar hur effektiv en sådan modell är. En känslighetsanalys utfördes på modeller skapade i Plaxis. Syftet med denna analys är att undersöka vilka faktorer som orsakar skillnader mellan modellerna och mätdata. Projektet ligger i centrala London och analysen fokuserar på tunneldeformationer orsakade av att två byggnader rivs. Tunnlarna befinner sig i ett lager av Londonlera under byggarbetsplatsen. En analys utfördes för att undersöka huruvida olika parameterar, olika materialmodeller och analysmetoder, 3D effekter och grundvattennivån påverkar tunnelförflyttningarna. Markundersökningar, labbtester och publicerad data användes som grund för att bestämma indatavärden. En 2D modell skapades i Plaxis genom att använda materialmodellerna Mohr-Coulomb och ”Hardening Soil with small-strain stiffness”. En Mohr-Coulomb modell skapades dessutom i Plaxis 3D. En känslighetsanalys utfördes sedan på 2D modellen för att identifiera vilka parametrar som påverkade tunnelförflyttningarna mest. Resultaten jämfördes med mätdata och viktiga parameterar ändrades för att ge bättre resultat. Inverkan av att ändra dessa värden undersöktes även i 3D modellen. Slutligen undersöktes påverkan av en förhöjd grundvattennivå. Resultaten antyder att jordens styvhet och den effektiva kohesionen har störst inverkan på resultaten. Styvheten vid små töjningar visar sig vara särskilt viktigt eftersom deformationerna år små. 3D modellen gav generellt sätt mer korrekta resultat än modellen i 2D. En högre grundvattennivå påverkade inte resultaten nämnvärt.

The deep mining industry and civil engineering need to perform rock stability analyses during excavation projects. These analyses are closely related with displacements in tunnel contours. The ground reaction curve is a powerful tool to characterize these displacements that is widely used in the New Austrian Tunneling Method. However, the analytical solutions that exist are only applicable under isotropic stress conditions for deep tunnels. This study aims to investigate when it is possible using the analytical methods to determine the ground reaction curves with enough accuracy in the case of shallow tunnels under anisotropic in-situ stress conditions. The method begins with a literature study. After that, with the help of a 2D model, a comparison between the analytical and the numerical solutions for ground reaction curves at different depths and at different initial in-situ stress ratios was carried out. The results show that both crown and floor displacements deviate more from the analytical solution than the wall displacement. The crown and floor can even move upwards under high initial in-situ stress ratios for shallow tunnels. Because of that, the analytical solution of the ground reaction curve at shallow depths under anisotropic stress conditions should not be used. In the case of isotropic stress field conditions for the analysis in this study, the results given by the analytical solution agree with the numerical ones at depths higher than 14 times the radius of the tunnel. On the other hand, the difference between numerical and analytical solutions becomes higher while increasing the initial in-situ stress ratio, even for very deep tunnels. Furthermore, an empirical equation to obtain the displacements of the ground surface, tunnel wall and tunnel crown has been obtained after a multiple linear regression analysis.

The effects of black polyethylene (PE) mulch alone and in combination with plastic film tunnels (Agronet, Reemay, whiteperforated, clear, and clear-slitted) were studied on morphology and yield of sweet corn in North Logan, Utah. Yields of "Miracle" sweet corn (Zea mays L.) were increased significantly by using black PE mulch and with a combination of various types of plastic row covers, as compared to unmulched soil. Standard-growth analysis procedures were conducted to verify responses among treatments. Treatment effects were determined by measuring days to first flowering, ear weight, number of side tillers, cob length, cob circumference, cob fill length, number of rows, and number of kernels missing per cob. Leaf area, plant height, and total shoot dry mass were significantly larger for mulched than for unmulched plants.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Robert Erik Grip. / M.S.

Subsonic wind tunnel investigations were conducted on a 60° swept, flat plate, delta wing with a leading edge vortex flap. The pressure distributions were measured over a range of angles of attack starting from zero to 40° in 5° interval and flap deflection angles from zero to 45° with 5° increments at a Reynolds number of about 2.14 x 10‘ based on the root chord. The flow visualization experiments were performed from zero degree to the stall angle, with ten different flap deflection angles at the same Reynolds number. The mean flow field was measured at angles of attack l0° and 15° with the flap deflection angles of l0° and 30° at a Reynolds number of about 1.50 x 10°. The experimental results shows that the leading edge vortex flap is an effective means to control the vortex flow over a delta wing. The optimum flap deflection angles were found where the primary vortex was confined to the leading edge vortex flap, thus producing a thrust on the flap. It was found that flap deflection could be used to restore a vortex flow from burst vortex condition. / Ph. D. / incomplete_metadata

<p dir="ltr">The Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) was used for a set of experiments studying the effect of isolated roughness elements on boundary-layer transition on a 7° half-angle cone. In quiet flow, the cone was tested at Reynolds numbers of 7.4 × 10e6 /m, 10.2 × 10e6 /m, and 13.0 × 10e6 /m. Tests were also completed at Re = 11.0 × 10e6 /m in noisy flow to examine the effects of freestream noise. The cone was set at both 0° and 6° angle of attack and an isolated, square trip oriented like a diamond with respect to the flow direction was attached before each set of runs. </p><p dir="ltr">Using infrared thermography and pressure transducers, the location of transition onset was estimated for each test. The results followed all expected trends: transition moved upstream as trip height increased, transition occurred earlier at higher freestream Reynolds numbers, and transition was significantly delayed in quiet flow compared to noisy flow. Mean flow solutions were generated to calculate correlation values commonly used to predict transition. Theexperimentaldatawasthenusedinconjunctionwiththesecorrelationvalues to identify a range of critical values that could be used to predict transition behavior. </p><p dir="ltr">Additionally, a z-type schlieren setup was developed for the BAM6QT. Various components were upgraded and standard procedures for aligning the system were developed. A new pulsed laser and high-speed camera were integrated into the system to enable schlieren imaging at up to 1.75M fps. The final configuration allows the schlieren system to be used for various applications with minimal adjustments, and has been utilized in many research projects in the BAM6QT.</p>

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.