Browsing by Subject "Tornadoes"
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Item A Preliminary Study in Missile Penetration of Residential Walls(Texas Tech University, 1973-08) Thompson, Raymond GeneNot Available.Item An analytical and numerical investigation of the Kuo tornado model(Texas Tech University, 2000-05) Vugrin, Eric D.The goal of this work is to present an analytical and numerical investigation of the Kuo tornado model. The derivations of the model and a more general solution are described. The effects of several parameters on the streamlines are examined, and numerical simulations and methods are presented to analyze the associated heat equation.Item An investigation of the relationship between ENSO and U.S. tornado climatology(Texas Tech University, 2000-05) Nagle, Seth R.The goal of this thesis is to examine the tornado frequency during different seasons in different zones of the eastern two-thirds of the continental United States, during different phases of ENSO. Recently, ENSO has also been examined in correlation with tornadic activity by Bove (1997). Bove (1997) found that during the La Nina phase of ENSO, there was a rise in tornadic activity in the Ohio and Tennessee River Valleys in the spring and early summer. He also found that in "Tornado Alley," which is the area of the central U. S. that annually receives the highest number of tornadoes, the tornadic activity decreased during the LN phase of ENSO. This approach to studying tornadic activity is more climate-oriented than previous research. The data in this thesis will be studied by season and by geographic area. This is because different parts of the country have different peaks in tornadic activity. For example, Anthony (1988) found that the peak of tornadic activity for the majority of the southeastern states is in April and May. In other parts of the country, such as the northern high plains, the peak tornadic activity is in June (Tecson et al., 1982). Changnon (1982) found that the peak tornadic activity in the state of Illinois is spread out over June, July and August. Also, it is important to know if the largest deviation from normal takes place during the most active part of the year for a particular area, especially if the departure from normal is an increase in the number of tornadoes. Using this information, possible relationships between ENSO and tornadic frequency of the eastern half of the CONUS will be exposed. The manner in which this subject is addressed is statistical. That is to say, conclusions about physical mechanisms will not be drawn from the results. After examining the results, it is hoped that performing statistical analyses on the data will substantiate any changes in the tornadic activity that were reflected in the data by revealing that the changes were not chance occurrences. This would be helpful since the ultimate goal is to be able to predict when and where tornadoes will occur. In this paper, a correlation between tornado climatology and the varying phases of ENSO will be investigated. In Chapter II, the data will be presented along with how it was processed. Chapter III will discuss the results of the data processing. Chapter IV will examine the statistics involved in this study. Conclusions and possible suggestions will be presented in Chapter V.Item Item Art Directable Tornadoes(2011-08-08) Dwivedi, RavindraTornado simulations in the visual effects industry have always been an interesting problem. Developing tools to provide more control over such effects is an important and challenging task. Current methods to achieve these effects use either particle systems or fluid simulation. Particle systems give a lot of control over the simulation but do not take into account the fluid characteristics of tornadoes. The other method which involves fluid simulation models the fluid behavior accurately but does not give control over the simulation. In this thesis, a novel method to model tornado behavior is presented. A tool based on this method was also created. The method proposed in this thesis uses a hybrid approach that combines the flexibility of particle systems while producing interesting swirling motions inherent in the fluids. The main focus of the research is on providing easy-to-use controls for art directors to help them achieve the desired look of the simulation effectively. A variety of controls is provided which include the overall shape, path, rotation, debris, surface, swirling motion, and interaction with the environment. The implementation was done in Houdini, which is a 3D animation software whose node based system allows an algorithmic approach to the problem and integrates well with the current tools. The tool allows the user to create animations that reflect the visual characteristics of real tornadoes. The usefulness of the tool was evaluated among participants who had some experience in 3D animation software. The results from the simulation and evaluation feedback reveal that the tool successfully allowed the users to create tornadoes of their choice efficiently.Item Donaldson-Sullivan tornado model(Texas Tech University, 2000-05) Mickel, Church E.The purpose of this paper is to analytically and numerically explore the Generalize Donaldson-Sullivan Tornado Model. Essentially, the Donaldson-Sullivan tornado model is a stationary solution of the Navier-Stokes equation. This solution was derived in the late 1950's and early 1960's and was believed to model a tornado. As the solution is quite complicated and almost impossible to analytically investigate, a numerical investigation is called for. As one will see. the Donaldson-Sullivan Tornado Model shares some qualities with those of an actual tornado. However, one will find that there are many more properties of this solution that do not appear to emulate a tornado. The case ^ / 1 or the Generalized Donaldson-Sullivan Tornado Model is another stationary solution of the Navier-Stokes equation. Like the Donaldson-Sullivan Solution, this solution is quite complicated and requires the use of numerical techniques to efficiently explore its properties. As one will see. this solution possesses some extremely interesting properties. However, it is the b(>lief of the au;hor (.[" ;';.:.- i^n^,: : that these properties do not accurately represent the behavior of a tornado.Item Finite element modeling of tornado missile impact on reinforced concrete wall panels(Texas Tech University, 1993-12) Zhang, YumingThis study describes a finite element model for the impact of large tornado missiles on reinforced concrete wall panels. The analysis predicts the dynamic response of wall panels when impacted by a missile with a large contact area such as an automobile. The development and current status of tornado-generated missiles and their impact effects on concrete wall panels are summarized along with the failure criteria for concrete material in the theory of plasticity. Quadratic finite elements are used to discretize the domain of the wall panel. Fundamental assumptions are based on the Mindlin and Reinsser's plate theories. An "embedded" model is employed to account for the reinforcing bars. The nonlinear behaviors of concrete and of steel bars are analyzed by means of rate-dependent constitutive relationships. A new strain rate-stress relationship is proposed, and the relationship between the fluid parameter 7 and the coefficient a is set up. A model is proposed to describe the initial and subsequent yield surfaces of concrete material, which avoids underestimation of the effect of high hydrostatic stresses on the yielding behavior of concrete. Ottosen's four-parameter failure criterion is used to define the failure surface of concrete. A crack monitoring algorithm accounts for post-cracking and post-crushing behavior of concrete. An explicit time integration scheme is used to solve the nonlinear dynamic equations carried out using the finite element discretization of a concrete wall panel. A computer program is developed in accordance with the above conditions.Item Flow visualization and fluid-structure interaction of tornado-like vortices(Texas Tech University, 2003-12) Fouts, John LyleA Ward-type tornado simulator has been built using a configuration of 16 slotted jets instead of a rotating screen to create the required far field circulation needed to produce a tornado4ike vortex. Flow visualization data, velocity data and pressure data were all obtained using the simulator. The produced vortices observed ranged from a laminar, rope-like, single-celled vortex to a turbulent, much larger diameter, two-celled vortex. Helium bubbles were used to visualize the vortices in the convergent region of the tornado simulator. At a=0.5, the low swirl ratios (the ratio of the tangential flow rate to the updraft flow rate) calculated were s=2.23 and at a=1 s=1.51. The high swirl ratios calculated were s=8.03 at a=0.5 and s=6.72 at a=1. The swirl ratios calculated are unique to the TTU TVS II. The initial vortex configuration in the TTU TVS II was that of a single-celled vortex. During flow visualization, as the swirl ratio was Increased, a breakdown bubble was observed moving down the vortex core region toward the surface of the simulator. Once the breakdown bubble has traversed the vortex core to the surface of the simulator, the vortex is defined as two-celled. The TTU TVS II was capable of producing single-celled and two-celled vortices. Pressure data was obtained on cubical and cylindrical models that were positioned at various radial locations within the simulator. The models were also subjected to moving tests through the TTU TVS II In order to compare the stationary data to the moving data. Using the pressure data, non-dimensional force coefficients were calculated and contour plots of the force coefficients on the cube and cylinder were generated for the stationary tests while, for the moving tests, specific points on the models were chosen, and the force coefficients at these points were plotted as a function of position In the TTU TVS II. The stationary tests show that both the cube and the cylinder models experience flow regimes at different points In the TTU TVS II similar in pattern to those induced by boundary layer-type flows, but mainly towards the outer regions of the simulator in low swirl cases (s=2.23 and s=1.51). Also for the cylinder, the contour plots indicate a horseshoe vortex forms around the cylinder. At the center of the simulator, both the cylinder and the cube disrupt the flow field significantly, and at this point, the flow field is very complex and at the present time the experimental equipment and data are not sufficient to quantify the flow In this region. The leading and trailing edges of the roof as well as the leading and trailing sides of each model were chosen and force coefficients were calculated and plotted as a function of radial position In the TTU TVS II for the moving tests. Each of these moving tests had approximately the same trends for the leading edge and side and the trailing edge and side with a few exceptions. The stationary test data followed the trends of the moving test data In most cases tested. This would mean that less significance could be placed on the much more complicated moving tests and more significance on the less complicated stationary tests In future testing Limited statistical analysis was also performed on the obtained data sets. This showed that standard deviation for all cases Is very small, so the distribution should be concentrated towards the center of the normal distribution. Most of the skewness values are negative Indicating the normal distribution is skewed to the right of the centerllne and slow, Infrequent variations In pressure below the mean. Very high kurtosis values like the ones shown for the center of the roof of the cylinder at the center of the simulator indicate an Increase In the high-frequency content of the fluctuating pressure signals read.Item High viscosity solutions of the Navier-Stokes equations modeling a tornado vortex(Texas Tech University, 2000-12) Baker, Joshua ThomasThis thesis will discuss several aspects of the Navier-Stokes system in cylindrical coordinates. We will highlight both the classical Donaldson-Sullivan solution and the recently discovered generalized Donaldson-Sullivan solution and will give their derivations. Our main focus will be on the following system and in particular the viscosity constant, v.Item Inelastic response of multistory buildings to tornadoes(Texas Tech University, 1977-12) Seniwongse, Muang-sa-ngopNot availableItem Numerical and analytical analyses of a tornado model(Texas Tech University, 1999-05) Schmitt, Patrick AlanDuring the course of this thesis work, we will be studying and analyzing one of the first tornado models derived from the Navier-Stokes equations for incompressible fluid called the Burgers-Rott model. We will completely present the model and its derivation, but will present this derivation autonomous from the original work. Our goal is to consider all cases of the model, including those which due to physical restrictions do not produce a tornado. In doing so, we will go beyond the original work by using computer simulation to graphically interpret our results.Item Radio noise emissions from severe local storms.(Texas Tech University, 1975-05) Nomikos, Constantinos EvangelouNot availableItem Simulated tornado wind fields and damage patterns(Texas Tech University, 1978-08) Metcalf, Dean RichardNot availableItem The 3 May 1999 tornado outbreak: radar and damage analysis for Oklahoma County(Texas Tech University, 2002-05) Shaw, Erin PatriceOn 3 May 1999, a number of violent tornadoes swept across the central United States. The state of Oklahoma endured the most devastating effects of this tornado outbreak, counting approximately 60 tomadoes, more than 40 deaths, and more than $1 billion in damages before the night was over. Storm A, the first of eight tomado producing supercell storms in central Oklahoma, spawned the deadliest, most destructive of these tornadoes. Data from the Twin Lakes, Oklahoma (KTLX) WSR-88D Doppler radar is examined in order to describe the structure of Storm A as it impacts Oklahoma County in central Oklahoma. Of particular interest is the radial velocity data, which offers insight into the general wind motion above the surface. This wind profile is compared to damage reports made in Oklahoma County, which include initial Fujitascale estimates and the tax assessor's damage reports. It is found that the radar-derived data accurately predicts the location of damage. Furthermore, Doppler velocity data also shows winds near the surface evolving in a manner similar to the damage itself. These results, along with their implications, are also discussed.Item The Tulia outbreak storm: mesoscale evolution and photogrammetric analysis(Texas Tech University, 1982-05) Rasmussen, Erik NelsSupercell thunderstorm structure and evolution is examined on several length and time scales using evidence from the 28 May 1980 Tulia Outbreak storm. Conventional meteorological data are combined with storm intercept team observations and photographic data to perform this analysis. New motion picture photogrammetry techniques are described and used for tornado analysis, and errors arising in photogrammetry are determined. It is found that the storm was triggered by a surface dryline, developed in a favorable environment, and intensified in an area of strong surface temperature gradients. After the storm collapsed it showed cyclic variations in intensity which corresponded to stages in cyclic tornado evolution. The photogrammetry results include a number of new findings. The three-dimensional flow structure is revealed and axial asymmetries are documented. In addition, time variations in tornado morphology, translation, and strength are documented.Item Wall barrier resistance to the impact of tornado-generated missiles(Texas Tech University, 1984-05) Bailey, James RobertNot available