Issue # 1, 2019

Posted by admin on 18 February 2019

Content

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RESEARCH ASSOCIATE POSITION AT COVENTRY UNIVERSITY (UK)
PHD POSITION ON ALFVEN WAVES AND MHD TURBLUENCE (GRENOBLE/CNRS/COVENTRY)
PHD POSITION ON MAGNETOCONVECTION BEYOND THE CHANDRASEKHAR LIMIT (GRENOBLE/COVENTRY/ILMENAU)
SCHEDULE OF CONFERENCES ON MHD AND RELATED TOPICS
NEXT HYDROMAG NEWSLETTER

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RESEARCH ASSOCIATE POST ON THE NON-LINEAR STATES OF CONVECTION IN THE EARTH CORE FUNDED BY THE LEVERHULME TRUST AT COVENTRY UNIVERSITY (UK)

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(from Alban Potherat, Coventry, UK )

A Research Associate position in theoretical fluid mechanics is offered at Coventry University (UK). The project concerns convection under a magnetic field in the so called “tangent cylinder” region of the Earth’s core. Much of the mystery surrounding the Earth’s dynamics (its magnetic field, plate tectonics) lies in the nature of the convective patterns within the Earth’s liquid core, and in particular in the region called the “Tangent Cylinder”. What are the possible convective states under the combined influence of the Earth’s rotation and magnetic field, and how erratic are they? This thesis is part of a theoretical and experimental research program funded by the prestigious Levehulme Trust (http://www.leverhulme.ac.uk), that aims at answering these questions. The purpose of this thesis is to theoretically predict the possible nonlinear convective states for the first time. We will then evaluate which of these states are mostly likely to underpin the Earth’s core convection.

The Research Associate will conduct the theoretical and numerical analysis of the problem under the joint supervision of Prof. Alban Pothérat (http://users.complexity-coventry.org/~potherat/index.html) and Dr Chris Pringle. The study will seek the possible structure of convection by means of advanced stability theory and branch tracking method, to unveil the possible states. In the frame of the research program, the work is purely theoretical/numerical and will be conducted in collaboration with an experimental study that will seek to reproduce and visualise these non-linear states in an experimental model of the Earth Core. Successful candidates are expected to hold a PhD in fluid mechanics or a related discipline, and to have demonstrated excellent abilities in mathematics and programming. The successful candidate will be part the vibrant team of internationally recognised academics and PhD students forming the fluid dynamics group within the Applied Mathematics Research Centre, whose work has been ranked at 83% world-class at the UK’ latest Research Excellence Framework in 2014. This unit is part of the Flow Measurement and Fluid Mechanics Research Centre, specialises in theoretical and experimental fluid mechanics. It is especially renowned for its work on magnetohydrodynamics (MHD), turbulence, stability and geophysical flows. The group closely collaborates with partner groups in world-leading institutions in Australia, China, France, Germany and the UK.

Informal enquiries are welcome: please forward a CV and academic records to Prof. Alban Pothérat (alban.potherat(at)coventry.ac.uk).

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PHD ON ALFVEN WAVES AND MAGNETOHYDRODYNAMIC TURBLUENCE AT GRENOBLE UNIVERSITY/CNRS/COVENTRY UNIVERSITY

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(from Alban Potherat, Coventry, UK )

Under the joint supervision of Alban Pothérat, (LnCMI Lab/CNRS and Coventry University) (http://users.complexity-coventry.org/~potherat/), Laurent Davoust (Grenoble-INP, SIMAP Lab) and François Debray (LnCMI/CNRS).

Applications are invited for a PhD (possibly including an MSC internship) in experimental fluid mechanics at the LNCMI-G (Grenoble High Magnetic Field Laboratory, http://lncmi.cnrs.fr/?lang=en). The topic concerns the experimental study of turbulence in liquid metals in a very high magnetic field. Turbulence is one of the major challenges of classical physics. Here, we seek to understand the role played by the propagation of magneto-mechanical waves (called Alfven waves) in the statistical and dissipative properties of turbulence and in its transition between two- and three-dimensional states. This type turbulence plays a key role in the dynamics of a number of astrophysical, geophysical, amongst which stellar accretion disks, planetary interiors but is also suspected to appear in engineering problems such as the cooling of nuclear fusion reactors. Until now, Alfven waves have been difficult to reproduce in laboratories because of the extreme conditions in which they appear (high Reynolds numbers and/or high magnetic fields).

The PhD student will be conducting an experimental project during which a turbulent flow is generated within a experimental device filled with liquid metal and placed inside of one the large magnets available at LNCMI in Grenoble, which are capable of producing some of the strongest magnetic fields in the world. In the extreme fields available at LNCMI, the electromagnetic force becomes propagative on the top being diffusive (propagation of Alfvén waves). The goal of this PhD is to use this unique combination of features to reproduce in the laboratory some of the mechanisms that occur in astrophysical or planetary systems and in the context of nuclear energy production, so as to understand them in detail.

The flow will be diagnosed by means of advanced metrology techniques such as ultrasound velocimetry and electric potential mapping. The PhD student will be in charge of running and improving the experimental device, interpreting the results so as to better understand the observed flow regimes. The combination of extreme magnetic fields and this unique experimental device developed by our joint team in Coventry and Grenoble offers for the first time a possibility to extensively map astrophysical and planetary phenomena that have been extremely difficult to probe direclty until now.

Applicants are required to hold, or be on course for an MSc in fluid mechanics or related speciality (Mathematics or Physics). To apply please forward complete academic records and CV to Alban Pothérat (Coventry University, alban.potherat(at)coventry.ac.uk, +44(0)2476 88 88 65), Laurent Davoust (Grenoble-INP, +33(0)476825206, Laurent.Davoust(at)simap.grenoble-inp.fr ) or Francois Debray, LNCMI (francois.debray(at)lncmi.cnrs.fr, +33(0)476 88 12 44). Informal contacts per phone or email are recommended.

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MSc+PhD ON MAGNETOCONVECTION BEYOND THE CHANDRASEKHAR LIMIT

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(from Alban Potherat, Coventry, UK )

Under the joint supervision of
Alban Pothérat, (Coventry University, UK, http://users.complexity-coventry.org/~potherat/),
Jörg Schumacher (Technische Universität Ilmenau, Germany, https://www.tu-ilmenau.de/tsm/ ),
François Debray (LNCMI/CNRS Grenoble, France, http://lncmi-g.grenoble.cnrs.fr/)

A PhD position in experimental fluid mechanics is open at the High Magnetic Field Laboratory in Grenoble (CNRS/ France). The topic concerns the experimental study of Rayleigh-Bénard convection under the influence of high magnetic fields. This type of convection plays a crucial role in numerous natural and industrial processes: for example in the tachocline layer of the Sun, in the liquid core of the Earth, but also in material processing such as the pulling of silicon ingots or the continuous casting of metallic alloys. In general, magnetic fields introduce a dissipative mechanism through the Joule effect which tends to damp, or even suppress convection. This has an impact on characteristic patterns that form in a convective flow. Chandrasekhar (Physics Nobel Prize 1983) derived the theoretical value of the critical Rayleigh number beyond which convection survives for a given magnetic field in the ideal case of a fluid layer confined between two infinite planes. Nevertheless, when lateral walls are present, convective plumes could potentially persist below this limit and thus locally promote enhanced heat fluxes.

This effect has, until now, never been observed in the laboratory, partly because typical electrically conducting fluids are opaque and thus hard to probe. The purpose of this PhD project is to observe the impact of strong magnetic fields on the formation of convective structures and to characterise these states and their possible transition into turbulent convection. For this, the student will be taking advantage of a new technique recently developed by the groups in Coventry and Grenoble, which consists of using a weakly conducting but transparent electrolyte placed in very high magnetic fields. This technique makes it possible to obtain precise maps of the velocity fields by means of advanced optical measurement methods using laser imaging technology (such as Particle Image Velocimetry or Laser Doppler Anemometry).

The PhD student will be in charge of this experimental project and will collaborate with theoreticians from TU Ilmenau in Germany who will be conducting numerical simulations of this problem in parallel, to compare the results.

Candidates must have a master degree in engineering or physics (300 ECTS credit points) and be motivated to conduct technically advanced experimental projects. Experience in fluid mechanics and/or measurement technology is welcomed. The PhD will benefit from a Co-tutelle between Coventry University (UK) and TU Ilmenau (Germany) leading to a PhD award in each university. The work will be physically based in the laboratory in Grenoble (France) for most of the time with extended stays at sites in the UK and Germany. The position runs for a period of three years and is expected to start in spring 2019.

To apply, please send a CV and a full transcript of academic records to:
Alban Pothérat (Coventry University, alban.potherat(at)coventry.ac.uk)
Jörg Schumacher (TU Ilmenau, joerg.schumacher(at)tu-ilmenau.de)
Francois Debray (LNCMI, francois.debray(at)lncmi.cnrs.fr ).

Informal enquiries are welcome. Please contact Alban Pothérat (+44 2476 88 88 65), Jörg Schumacher (+49 3677 69-2428) TU Ilmenau, or François Debray (+33 4 76 88 12 44), LNCMI.

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SCHEDULE OF CONFERENCES ON MHD AND RELATED TOPICS

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