School of Physics Thesis Dissertation Defense

Presenter:        Wesley Toler

Title:                     Using exact coherent structures to describe the dynamics and statistics of intermittent Taylor-Couette flow

Date:                    Thursday, July 25, 2024

Time:                    1:00 p.m.   

Location:           Howey Physics Building, N201/202

Virtual Link:     https://tinyurl.com/28a5sprp

Committee members: 

Dr. Michael Schatz, School of Physics, Georgia Institute of Technology (advisor)

Dr. Predrag Cvitanović, School of Physics, Georgia Institute of Technology 

Dr. Ari Glezer, George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology  

Dr. Roman Grigoriev, School of Physics, Georgia Institute of Technology 

Dr. Kurt Weisenfeld, School of Physics, Georgia Institute of Technology

Abstract: 

A dynamical systems approach to understanding turbulence suggests that the complicated motion of the turbulent flow is shaped by special solutions to the Navier-Stokes equations known as exact coherent structures (ECSs). In this picture, turbulent flow co-evolves with, or "shadows", one such solution for a time; then a different ECS; and so on. This qualitative picture has recently been confirmed quantitatively at certain Reynolds numbers in experimental turbulent Taylor-Couette flow. Here we apply a similar methodology to an experimental Taylor-Couette flow that has the property of intermittency, wherein the flow exhibits a high degree of regularity for certain intervals punctuated at other times by significant increase in spatial and temporal variation of the flow. A collection of ECSs is found that describes the behavior of the flow for almost the entire duration of the flow, in both experimental and numerical investigations, for both quiescent and active behaviors of the flow. It is also demonstrated that the transition of flow behavior between quiescent and active regions is mediated by a specific ECS that connects both regions. Finally, observables of the flow are shown to be well-represented by weighted averages of ECS observables, thereby demonstrating the connection between dynamical shadowing of ECSs and average observables in a 3-dimensional experimental flow.