Science Journey: Chaos, Turbulence, and the Beauty of Uncertainty in Complex Systems
Tanner Harms
Aerospace graduate student
About the Presentation
Turbulence • Fluid Dynamics • Data Science/Artificial Intelligence
What is Chaos Theory? Chaos Theory is the study of complex systems whose behavior is extremely sensitive to changes in initial conditions. One particularly good example of this type of system is turbulence in the flow of liquids and gasses. Though often associated with uncomfortable airplane rides, turbulence is a phenomenon that occurs just about everywhere we can imagine and is therefore quite important to study. However, it is such a complicated phenomenon that, despite more than 100 years of research, turbulence continues to perplex and inspire brilliant scientists of all kinds. In this talk, I will discuss my approach to studying turbulence using what are called Lagrangian Coherent Structures. Along the way, I'll explain how principles from dynamical systems theory relate to my trajectory as a scientist, and how what I've learned in the laboratory informs the way I understand the human experience.
About the Speaker
Tanner Harms is a PhD candidate in aeronautics in the McKeon Lab at the Graduate Aerospace Laboratories at California Institute of Technology (GALCIT). His research focuses on developing measurement techniques for specific features in complex flows called Lagrangian Coherent Structures. These features have a variety of applications including reducing pollution in the ocean, understanding how birds and fish navigate and feed, and engineering better mixing systems like the fuel injector inside a rocket engine.
Tanner grew up in Denver, Colorado, as the son of Adley and Jenifer Harms. Adley works for the engineering software company Autodesk as a business professional, and Jen is a graphic designer who retired to raise Tanner and his brother Mason. Tanner was a very curious child and his parents worked hard to provide opportunities to explore the world of STEAM (science, technology, engineering, art, and mathematics). He was an active child who spent much of his time playing sports, his favorite of which was wrestling. Upon graduating high school, Tanner chose to study mechanical engineering at the University of Wyoming (UW) where he pursued a collegiate career as a heavyweight wrestler.
While in college, Tanner's interest in engineering grew, leading him to pursue a master's degree in mechanical engineering at UW, studying with Professor Jonathan Naughton. During that time, Tanner used wind tunnel experiments to study the unsteady aerodynamics of helicopter and wind turbine blades—and coached the UW wrestling team on the side. With the encouragement of various mentors, Tanner decided to pursue a doctoral degree focusing on the data analysis methods used in fluid mechanics. This ultimately led him to Professor Beverley McKeon's lab at Caltech.
When he is not studying or doing research, Tanner enjoys going on adventures with his wife, Jessica, doing just about anything active, and learning about new subjects unrelated to his research. He still enjoys wrestling and grappling, regularly coaching at a Pasadena gym and practicing Brazilian Jiu Jitsu, and he is a member of a local Presbyterian church.
Vocabulary
Enrich your knowledge around the lecture topic by reviewing relevant terms, provided by Tanner.
A system in which the state of a point in space changes over time. Take for example these systems: particles moving through the air or cars driving on the road. The point in space would be a particle or a car, and the state could be their position, speed, and acceleration.
The branch of mathematics that studies dynamical systems that are highly sensitive to initial conditions. Initial conditions refer to a state at the time it is first measured (see examples of "state" above). In chaotic systems, seemingly small changes early on can result in significant changes much later.
The branch of physics which studies the behavior and properties of liquids and gases (in this case, both are considered fluids). Fluid mechanics can be broken into fluid statics, which studies fluids at rest, and fluid dynamics, which focuses on fluids in motion.
Laminar flow is smooth fluid motion in which particles move in parallel paths with no cross currents or eddies (swirling motions) to mix the fluid.
Turbulence is the chaotic motion of fluids (liquids and gases).
Activity for the Classroom
You've likely already encountered some everyday examples of turbulence. Smoke billowing off a campfire, for example, or milk swirling into coffee, or water rushing over and around rocks in a stream. Here's another way to observe the phenomenon up close:
- Take a small, clear drinking glass or plastic bottle and fill it partially with water.
- Next, add a few drops of food coloring and observe the flow of the dye.
- How would you describe it? Do you notice any patterns?
- Take another glass or bottle and again, fill it with water.
- This time, drizzle some honey inside.
- How is the flow of the honey different from that of the food coloring? Why do you think that might be?
— Adapted from the Science Museum of Virginia
Recommended Resources
Keep the conversation going: Tanner Harms suggests the following videos, websites, and books for students and educators who want to learn more about fluid dynamics and turbulence—and science in general!
For general scientific videos, I really like the YouTube channel Veritasium. He covers lots of topics in science at an accessible level and even featured my advisor, Professor McKeon in a video on turbulence!
More from Veritasium on fluid flows and on chaos:
- 3 Ways Of Seeing Invisible Air Flow
- Chaos: The Science of the Butterfly Effect
- Risking My Life To Settle A Physics Debate
- The Most Misunderstood Concept in Physics
My other YouTube channel recommendation is about engineering: SmarterEveryDay.
He also has some cool videos on fluid mechanics:
- Why Laminar Flow is AWESOME
- Unmixing Color Machine (Ultra Laminar Reversible Flow)
- Two Vortex Rings Colliding in SLOW MOTION
- The WALKING WATER Mystery (in SPACE and SLOW MOTION!)
Here are a few more for cool visualizations:
- Droplet Collisions at 5000fps - The Slow Mo Guys
- 360 Slow Motion - The Macro Room
- Ink In Motion - The Macro Room
- A mesmerizing video of colorful fluids in high definition: MAGIC FLUIDS HDR
Books about technical topics related to my Science Journeys talk:
- Books by Steven Strogatz, in particular Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry, and Engineering and Sync: The Emerging Science of Spontaneous Order
- Chaos: Making a New Scieice by James Gleick
- Mathematics for Human Flourishing by Francis Su, and his excellent article, "The Lesson of Grace in Teaching" (Su is actually a local of Pasadena. He is a professor at Harvey Mudd College and was the president of the Mathematical Association of America. His writing explores the beauty and virtue intrinsic to studying mathematics.)
Some web resources:
- First, my collaborators' sites! Beverley J. McKeon and Steve Brunton, both excellent scientists and people.
- Other researchers who do work in this field include John Dabiri at Caltech and George Haller at ETH Zurich.
- Here is a website that has many (possibly hundreds!) of scientific demos that students can play around with: NetLogo Web: Fireworks
- Finally, I recommend the Substack of Pasadena local and Harvey Mudd professor Josh Brake, who explores life in the constantly evolving landscape of modern technology.
About the Series
In Science Journeys, Caltech graduate students and postdoctoral scholars share their research to inspire scientific curiosity. Programs are designed for middle and high schoolers, but all are welcome.
These programs are made possible through the generosity of the Friends of Beckman Auditorium.
If you have questions, please email Mary Herrera at mhh@caltech.edu.