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discovered_01_2013

discovered 01.13 FOCUS WWW.Hzdr.DE Where do you stand now and what are the next milestones? _FS . Construction started in April, we placed our order for the precession machine back in November 2012, we already have a rough draft for the experiments to model magnetic instabilities, and at this point we’re hard at work filling in the details. _PK . Exactly. We’re right in the middle of a stage where the technological model is being tested in different directions and its plausibility validated with the help of computations done at the TU Dresden. Given the various control interfaces with the building management system and savings of almost one million Euros, we decided to design the control system within the department of research technology. _FS . By this year, construction will be more or less complete. Next, construction of the dynamo and its various components will begin. The building will be built at the same time. Construction of the interior will commence in 2014 and that is the earliest we will be able to start to think about implementing the experiments. I’m guessing that we will tackle the first installations for the dynamo experiment in 2015. Initially, we will continue with the water experiments, not just as preparation but also because they have their own scientific value. After all, there have never been precession experiments at such high Reynolds numbers. _PK . Of course, all of this has a high inherent technological value. Presently, it is not possible to simulate the entire machine including the different flux modes. _FS . Because this time it’s all about a completely free flow in all three spatial directions. Nobody is able to simulate something like this. Today, we perform computations with Reynolds numbers of up to 10,000, and the end of the flagpole follows soon thereafter. However, as part of our experiment, we’re looking at Reynolds numbers of 85 million. We can only guess at the scaling of the precession powered flow in-between. Which is why we did the water experiment - with a Reynolds number of 1.6 million, after all - and are thus hoping to minimize the remaining risks. It’s already yielded a few rather exciting results. As such, we were able to observe, for instance, abrupt changes from laminar to turbulent flow, with highly interesting effects. We took initial speed measurements using ultrasound and we’re in the process of installing a cutting-edge 3D particle- image-velocimetry system to allow us to measure the flow completely for the first time. All of this is of great importance to the sodium dynamo’s success. But, in any case, we’re looking at a scientific remaining risk and are not able to say with a hundred percent certainty whether or not - and if so, then in what parameter range - the dynamo will work. Which collaborations are important for DRESDYN? _FS . DRESDYN was conceptualized as a European research platform and benefits from diverse collaborations. I think it’s important to mention the Helmholtz alliance LIMTECH, where several projects that directly latch onto DRESDYN, are located. Including a project with Göttingen University and AIP, the Leibniz Institute for Astrophysics in Potsdam: Andreas Tilgner, one of the World’s leading experts in this field, performs calculations for the precession dynamo, while the AIP wants to continue to work with us in the area of magnetic instabilities. In addition, it is our special concern that we coordinate with the international dynamo community like Dan Lathrop at the University of Maryland. However, DRESDYN will not be a user facility in the strictest sense of the term; for safety concerns, that’s just not possible. But we’re happy about all the various proposals for sodium-based experiments we can work on together as part of long-term collaborations. ContaCt _Institute of Fluid Dynamics at HZDR Dr. Frank Stefani f.stefani@hzdr.de _Department of Research Technology at HZDR Dr. Peter Kaever p.kaever@hzdr.de FUTURE PROJECT DRESDYN: Between 2013 and 2015, the World's first ever precession dynamo will be built on the HZDR campus. Image: Wörner & Partner Planungsgesellschaft mbH

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