Abstract Details
Abstracts
Author: Norman M Cao
Requested Type: Poster
Submitted: 2024-04-11 10:57:10
Co-authors: D.Qi
Contact Info:
Institute for Fusion Studies, the University of Te
1 University Station
Austin, TX 78705
USA
Abstract Text:
Turbulent flows frequently exhibit spatiotemporal intermittency, reflecting a complex interplay between driving forces, transport, and dissipation. When this intermittency manifests as observable structures in the flow, the characterization of turbulence becomes challenging due to the nontrivial statistical correlations introduced into the turbulent fields by these structures. In this work, we use tools from dynamical systems theory to study intermittency in the Dimits shift regime of the flux-balanced Hasegawa-Wakatani (BHW) equations, which model a transitional regime of resistive drift-wave turbulence in the plasma edge. First, we show in direct numerical simulations that turbulence in this regime is dominated by strong zonal flows and coherent drift-wave vortex structures, which maintain a strong linear character despite their large amplitude. Using the framework of generalized Liouville integrability, we develop a theory of integrable flows in generic fluid and plasma systems and discuss how the Lagrangian flows induced by the zonal flows plus drift waves exhibit a form of near-integrability originating from a fluid element relabeling symmetry. Finally, we use an exact stochastic Lagrangian representation of vorticity transport based on the Feynman-Kac formula to demonstrate how this nearly-integrable spatiotemporal flow patterning reinforces, rather than destroys the large-amplitude vortex structures. These findings illustrate the key role that coherent Lagrangian flows can play in organizing aspects of spatiotemporal intermittency in turbulent flows.
Comments: