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Nom de l'encadrant
Ivan Delbende
Contact
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Titre
Short wave instabilities on helical vortices
Descriptif
CONTEXT
Wind turbine wakes are dominated by a set of interlaced helical vortices which surround a region of velocity smaller than the wind velocity. Several instabilities develop on such vortices: displacement modes that bring vortices closer with one another, and short wavelength instabilities able to destroy them. Their study is thus of interest for the application with respect to wake recovery and interactions between wind turbines in farms, but also from a fundamental point of view. The work proposed during this internship concerns short-wavelength instabilities, which develop through a coupling between neutral vortex modes and core deformations : modes can interact with the vortex curvature leading to curvature instability ; vortex core deformation can also cause elliptic instability.

CONTENT
A HPC tool for analyzing the linear temporal stability of infinite helical vortex systems has been developed in FORTRAN. Using the linearized Navier–Stokes equations, it computes linear modes with arbitrary wavelength prescribed along the vortex, and provides their growth rate and spatial distribution. During this internship, we propose
a) to read and understand some recent papers that present analytical formulae for the growth rate of the short wave instabilities,
b) to run the numerical code, which is free from some of the assumptions done in the analytical work. Computations will be run on a supercomputer.
c) to compare numerical and analytical results,
d) to prepare initial states for subsequent nonlinear fully 3D simulations of helical wakes.

CANDIDATES
Candidates should have a strong interest in instability theory, high performance computations, modelling and visualisation in CFD.
Domaine
mécanique des fluides: instabilités et turbulence
Mots clés
  • STAGE POURVU
Niveau
M2
Groupe(s)
ETCM
Date de début
2019-03-04
Durée
5 mois

LIMSI
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Rue John von Neumann
F - 91405 Orsay cedex
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