1999 Nonlinear analysis of dynamics underlying cylindrical liquid jets
02/01/2010
Jérôme Godelle
Defended on June 22, 1999.
Ph’D Thesis
Abstract :
In this thesis, a study of the atomization of cylindrical water jets
with tools belonging to the theory of nonlinear dynamical systems is
proposed. This original study begin with an introduction on the
field of atomization and the theory of nonlinear dynamical systems.
The first part of this work allows to define precisely the measured
quantity recorded by a light scattering technique, by means of
analytic and numerical computations. An artefact on the measurements,
limitating their interpretation for an excited and a free water jet,
is identified. However, the first results are in agreement with the
theories (Rayleigh and Weber) and show that the dynamics of perturbations,
evolving along the jet, is characterised by "intermittent bursts".
To remove the artefact, a shadow technique is developped and compared
to the precedent one. The measurements are then shown to be linearly
related to the jet diameter for any perturbation amplitude.
Type-I phase intermittency is pointed out. In the case of free jets,
this intermittency is also observed although in a less obvious way.
When the flow velocity profile acts as the principal components on the jet
breakup mechanisms, the deterministic dynamics is lost. In this case,
we also observe that early initiations of perturbations imply a reducing
of the breakup length.
A statistical symbolic dynamics allows to precise the nature of the
behaviours observed for different control parameters in the case of
free jets : the dynamics of the jet subject to the velocity profile
action, which can be seen as a destabilisation of the flow toward
turbulence, is of stochastic nature ; while deterministic dynamics
could be described by a complete binary symbolic dynamics.
Abstract :
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MàJ . 16/05/2026