Section: New Results
Physics
Physical studies
Parallel Kelvin-Helmholtz instability
Participants : Hervé Guillard, Marco Bilanceri, Céline Colin [CEA] , Philippe Ghendrih [CEA] , Giorgio Giorgiani, Boniface Nkonga, Frédéric Schwander [M2P2, AMU] , Eric Serre [M2P2, AMU] , Patrick Tamain [CEA] .
In the scrape-off layer (SOL) of tokamaks, the flow acceleration due to the presence
of limiter or divertor plates rises the plasma velocity in a sonic regime.
These high velocities imply the presence of a strong shear between the SOL and
the core of the plasma that can possibly trigger some parallel shear flow
instability. The existence of these instabilities, denoted as parallel
Kelvin-Helmholtz instability in some works have been investigated
theoretically in [51] using a minimal model of electrostatic turbulence
composed of a mass density and parallel velocity equations.
This work showed that the edge plasma around limiters might indeed be unstable
to this type of parallel shear flow instabilities.
In this work, begun in 2013, we have performed large scale 3D simulations using
the PlaTo platform of the
same simple mathematical model to investigate this question.
The numerical results confirm that in agreement with the theoretical expectations
as well as with other numerical methods, the sheared flows in the SOL are subject
to parallel Kelvin-Helmholtz instabilities. However, the growth rate of these
instabilities is low and these computations require both a sufficient spatial
resolution and a long simulation time. This makes
the simulation of parallel Kelvin-Helmholtz instabilities a demanding benchmark but
it also allows us to validate the parallel implementation of the PlaTo platform up to
up to