Browsing by Subject "Wind tunnels"
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Item A ridge and clod wind erosion model(Texas Tech University, 1986-12) Arika, Caleb NyaangaTillage to create a cloddy, ridged soil surface in areas lacking residue or any form of vegetation cover, has been determined to be an effective method for wind erosion control. Emergency tillage during a dry, windy period creates a rough soil surface which helps reduce soil blowing until vegetative cover can be established or other more permanent control practices are adopted. A wind tunnel study on clods and ridges showed clods to be a more effective wind erosion control method than ridges. This points out the need for inclusion of clod cover as a separate and important factor in studies on wind erosion mechanics, erosion control, and estimates of^soil loss with equations such as the current USDA wind erosion equation. The data from this study verified a new erosion model under development at Texas Tech University. A conflict between the two literature reviewed was explained.Item Flowfield characterization of a gust generator(Texas Tech University, 1999-12) Fernandez, Viju JohnWindstorms such as hurricanes and tomadoes cause fetalities, injuries and have a significant societal impact. Insurance companies estimate that windstorm-related events account for up to seventy percent of their payout each year. An accurate understanding of the wind gusts that form these storms is therefore essential for damage mitigation. An active wind gust simulator was constructed which used NACA 0012 and derived airfoils to generate coherent structures in a turbulent wake, which simulated wind gusts. A constant Re = 1.9x10^^ (based on airfoil chord length) parametric study of the effects of different Strouhal numbers (4.14, 6.21 and 8.56) based on airfoil chord length, airfoils (NACA 0012, NACA 0006, NACA 0024, NACA 6412, NACA 6812) and angle of attack (10° and 20°) on three different diameter cylinders (0.2c, 0.4c, 0.6c, where c is the chord length) was conducted to study the growth, development and dissipation of coherent structures produced by the airfoil wakes and their interaction wdth those bluffbodies. Turbulent transport mechanisms and entrainment in the wakes associated with the production of a mixing layer forther downstream was also investigated. A CCD camera was used to visualize the flowfield generated. Processed flowfield images of the different conditions show a strong influence of the Strouhal nimiber, airfoil spacing and type on the flowfield produced and the nature of the wake interactions. Increasing the Strouhal number resuks in an energetic wake that does not dissipate quickly downstream in the flowfield. Decreasing the airfoil separation distance breaks down the large-scale structure of the wakes by adding additional momentum to the flow and enhancing the mixing and thereby the dissipation. The large deflection angle change does not have a significant effect of the type of structures shed from the airfoil trailing edges; it however increased the initial amplitude of the structures. The camber of the airfoils creates a fine scale turbulent flowfield by directing the flow in the direction of the airfoil tip and dissipating upon being deflected once again by the tunnel test-section wall. Any large-scale structures are quickly dissipaíed within half a lengthscale downstream of the airfoils. The flat plate wake creates structures with little entrainment and dissipation. The large-scale sinusoidal structures in the flat-plate wake maintain their size with little growth and dissipation until 3 length scales downstream. The structures caused by the NACA 0024 airfoil have a k)wer fi-equency and higher amplitude that the NACA 0012. They however behave in the same manner downstream.Item Re-design of a drive system for a low-speed wind tunnel(Texas Tech University, 1998-05) Walker, Todd D.The Thermal Systems Lab at the Texas Tech University Mechanical Engineering Department has an instructional wind tunnel. An improvement was made to the drive system of the tunnel so that the average test section velocity would increase. This involved the design and manufacture of a 2 ft. diameter fan as well as some modifications to the tunnel. The results were a 21% increase in the efficiency of the drive system and a 19 mph increase in the test section velocity.Item Simulated sandstorm injury to onions and potatoes(Texas Tech University, 1978-08) Thomas, David GeraldNot availableItem Vibration and flow field characteristics of a hemispherical solar concentrator(Texas Tech University, 1984-12) Foran, Richard KellyNot availableItem Wind engineering research field laboratory site characterization(Texas Tech University, 1995-12) Campbell, Jill AnnWind flow parameters obtained from the field data are simulated in the wind tunnel for studying wind effects on structures. The wind flow parameters include power law exponent (a), surface roughness (zo), shear velocity (u*), and longitudinal, lateral, and the vertical turbulence intensity (lu, Iv, and I^). The results of the wind tunnel study depend on the reliability of wind flow parameters measured in the field and the simulation technique. The objective of this work is to investigate the characteristics of the wind flow parameters at the Wind Engineering Research Field Laboratory (WERFL) in light of the factors which may affect the parameters. The factors investigated include: mean wind direction, mean wind speed, stationarity, atmospheric conditions, time of day a record was collected, and time of year a record was collected. The National Science Foundation has sponsored a Colorado State University/Texas Tech University Cooperative Wind Engineering Program at the Texas Tech University Wind Engineering Research Field Laboratory (WERFL) to study wind effects on low-rise buildings. Wind and meteorological data are collected on a 160 ft high meteorological tower. The data collected for this project includes wind speed and wind direction at four levels on the meteorological tower. Wind speed and direction were used to assess the wind parameters and perform the characterization of the terrain. The scope of this project is limited to data collected between April of 1991 and June of 1992 (Mode 15 data). A total of 465, 15-minute records were collected of which 454 records were found to be acceptable for analysis. The analysis of the data included plotting of the parameters versus the factors, estimation of probability density functions for the parameters, and nonparametric statistical testing. Interpretation of the analyses and observations from the data analysis revealed wind from all directions does not yield the same mean and variance of the parameters. The wind parameters show that stationarity is not an important factor for the site characterization. Shear velocity is a function of wind speed.Item Wind tunnel blockage corrections: a computational study(Texas Tech University, 2004-08) Sahini, DeepakWind tunnel blockage testing has been a wide spread traditional practice in the automobile industry for many years; but the tests conducted have been associated with the so called blockage effects, which arise due to the constrained flow nature inside the wind tunnel test section and over the blockages. These blockage effects need to be corrected in order to comprehend the test results similar to those of the actual road conditions. CFD has emerged as a tool to determine the blockage effects and provide corrections using computational techniques. In this present study, two such CFD packages, namely PHOENICS and AIRFL03D, are used for determining the wind tunnel blockage effects. The problems taken into consideration are both two dimensional and three dimensional flow cases. The test section domain height is varied so as to produce different blockage ratios, keeping the blockage dimensions constant. A two dimensional free stream case with blockage l/h ratio variation is tested and compared with experimental results. In the other cases, the two packages are compared with each other for pressure and velocity distributions and drag coefficients. A grid independent study was performed for one case. Finally, blockage correction equations are obtained for all the test cases.