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.
Key words : Nonlinear dynamical systems - Phase intermittency - Symbolic dynamics - Instability - Cylindrical liquid jet - Shadow/Extinction technique - Atomization.
Jérome Godelle is now "Ingénieur de recherche Dynamique du véhicule" for Renault.