Magnetohydrodynamics and dynamo effect.

For my PhD, I worked on magnetohydrodynamics and turbulence and their applications to the experimental study of the dynamo effect in the Von-Karman Sodium experiment .

In electrically conducting fluids, the electromagnetic field is coupled with the fluid motion by induction effects. We studied different magnétohydrodynamics phenomena, using two experiments involving turbulent flows of liquid metal. The first mid-sized uses gallium. The second, using sodium, is conducted within the VKS (Von Karman Sodium) collaboration. It has led to the observation of the dynamo effect, namely converting a part of the kinetic energy of the fluid into magnetic energy. We have shown that, depending on forcing conditions, a statistically stationary dynamo, or dynamical regimes of magnetic field can be generated. In particular, polarity reversals similar to those of Earth’s magnetic field were observed. Meanwhile, experiment with Gallium has been developed to study the effects of electromagnetic induction by turbulent flows in a more homogeneous and isotropic configuration than in the VKS experiment. Using data from these two experiments, we studied the advection of magnetic field by a turbulent flow and the induced fluctuations. The development of probes measuring electrical potential difference allowed us to further highlight the magnetic braking of a turbulent flow of Gallium by Lorentz force. This mechanism is involved in the saturation of the dynamo instability.

Experiment studying effect of an external magnetical field on a turbulent flow of gallium located at LPS ENS PARIS.

Opened tank of the Von-Karman Sodium (VKS) experiment located in Cadarache(CEA).

Reversals of magnetic field generated by dynamo effect in the VKS experiment. From Berhanu et al. 2007 EPL 77 59001

Related publications about gallium experiment :

Related publications about VKS experiment :

Documents (mostly in French) :

My PhD dissertation Turbulent magnetohydrodynamics in liquid metals

Slides de ma soutenance de Thèse

Poster sur les oscillations et les renversements dans VKS présenté à l'Euro MHD 2008.

Oral presentation " New results on the experimental VKS turbulent dynamo " présented in the meeting of European Geophysical Union (Vienna) in 2008.

Présentation sur les oscillations et les renversements dans VKS présenté au GDR dynamo 2008.

Poster sur le comportement "turbulent" du champ magnétique dans la dynamo VKS présenté à Euler’s Equations: 250 Years On.

Poster sur les mesures dans l'expérience D24 Gallium présenté au GDR Dynamo 2007.

Rapport de stage de Master 2

Présentation sur les mesures en champ localisé sur VKS2 aux rencontres du non linéaire 2006.

Poster au sujet de mesures hydrodynamique de l'expérience D24 Gallium pour les rencontres du non linéaire 2007.