Banca de DEFESA: Ana Luiza Piragibe Freire

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Ana Luiza Piragibe Freire
DATE: 18/12/2023
TIME: 10:00
LOCAL: Videoconferência via Plataforma ZOOM
TITLE:

ROLE OF LAGRANGIAN VORTICES AS MATERIAL TRANSPORT BARRIERS IN A MODEL OF TOKAMAK PLASMAS

KEY WORDS:

fusion plasma, low-to-high confinement, Lagrangian coherent structures, finite-time Lyapunov exponent, material transport barriers

PAGES: 52
BIG AREA: Engenharias
AREA: Engenharia Mecânica
SUMMARY:

In fusion plasma, numerical simulations are commonly employed to investigate the confinement properties of plasma in the bulk region of tokamaks. The modified Hasegawa-Wakatani (MHW) equations are used to model the behavior of plasma, which enables us to understand the radial transport in two-dimensional numerical simulations of electrostatic resistive drift-wave turbulence. By utilizing the MHW equations, we have gained insights into the low-to-high confinement (L-H) transitions that occur spontaneously in the plasma when it moves from a low confinement stage, characterized by turbulent flow, to a turbulence-suppressed regime known as zonal flow. To investigate these transitions, we vary the value of a control parameter \(\alpha\), which is related to adiabaticity, in numerical simulations, and observe the transition between the two regimes. This simplified model of L-H transitions can provide valuable information for tokamaks. The chaotic mixing properties of the flow are characterized by means of Lagrangian coherent structures (LCS). First, we compute the finite-time Lyapunov exponent (FTLE) of the calculated velocity field derived from the electrostatic potential to better characterize the chaotic mixing of the turbulent and zonal flow regimes. Then, we compare the statistics of the chaotic mixing of the two regimes using probability distribution functions (PDFs). Lastly, we identify the Lagrangian vortices using geodesic theory to further our understanding of the chaotic mixing of the two regimes, by also implementing the calculation of the kinetic energy for the vortices and total domain. These results can contribute to the understanding of turbulent transport processes in magnetic confinement fusion plasmas.

COMMITTEE MEMBERS:
Externo à Instituição - ERICO LUIZ REMPEL - ITA
Externo à Instituição - JUAN PABLO DE LIMA COSTA SALAZAR - UFSC
Interna - 1193378 - POLLIANA CANDIDA OLIVEIRA MARTINS
Presidente - 1906134 - RODRIGO ANDRES MIRANDA CERDA