Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Savory, Eric

2nd Supervisor

Orf, Leigh

Affiliation

University of Wisconsin-Madison

Co-Supervisor

Abstract

Tornadoes present an ever-increasing threat to communities worldwide, especially those with geographic conditions that place them in the path of several tornadoes annually. These conditions are likely to be exacerbated by ongoing trends in the climate. As such, it is necessary to move towards experimental and numerical tornado-like vortex studies that allow for more advanced simulation methods. Novel techniques for tracking and analysing tornado vortices simulated at high spatial and temporal resolution are presented herein. Significant wandering of the tornado's position and large peaks in the velocity field can be captured, demonstrating tangential gusting at more than 1.5 times the conventional peak average value. These gusts were also demonstrated to occur over a wider range of distance from the tornado centre than previous methods would detect. Finally, recommendations for spatial and temporal scaling of the results of conventional analyses are presented to guide the future of tornado-like vortex research.

Summary for Lay Audience

When reading the word "tornado", most people would likely imagine a funnel of rotating air touching from the sky to the ground, leaving destruction in its path. Though this may seem simple to replicate in a laboratory or computer model, simulating a realistic tornado is not trivial. There are many types of tornadoes and parameters that characterize their motion. The most notoriously difficult phenomena to capture in simulations are the presence of asymmetry about the vertical axis of rotation and the tilting of the vertical axis resulting from motion of the tornado vortex. Wind engineering studies published today can generate tornado-like vortices but are often not able to replicate these additional complexities or exclude them from their analyses. This work presents novel a method to use tornado velocity wind-fields to pinpoint the location of a vortex's centre in time and space in a consistent manner. By considering the spatial and temporal variation of the velocity data it is possible to determine not just the average velocity but also its expected range and other statistics. A timescale is defined for the average duration of a rotation of a tornado, which is useful in separating rapid fluctuations from the mean motions. Another scale introduced details how much a tornado's velocity varies in space from the velocities averaged over the circumference. This permits the use of conventional, simplistic velocity measurements to compute the range of expected velocity values. As a result, the tornadoes produced in any given simulation (so long as there are sufficiently well-resolved data available) would more accurately represent the real-world natural phenomena. This is especially important considering that these simulations are often used to design infrastructure and protect lives in future severe weather events.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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