Optimierung einer praezessions-getriebenen Stroemung fuer die Magnetfelderzeugung beim DRESDYN Dynamo Experiment.
Astrophysik und Astronomie
Statistische Physik, Nichtlineare Dynamik, Komplexe Systeme, Weiche und fluide Materie, Biologische Physik
Zusammenfassung der Projektergebnisse
Precession has long been considered an efficient mechanism for driving flows in the liquid part of planets, which in turn could be an alternative source for powering the geodynamo or the ancient lunar dynamo, which has motivated the experimental realization of a precession dynamo at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) within the project DRESDYN. This precession dynamo experiment is under construction and will provide a flow of liquid sodium in a cylindrical cavity with a magnetic Reynolds number of up to Rm = Ωc R2 /η ≈ 700. (defined with the achievable angular velocity of the cylinder Ωc = 63 s−1 , the radius R = 1 m, and the magnetic diffusivity of liquid sodium η = 0.09 m2 /s). Numerical models that are specific for the planned experiment indicate that it might be rather difficult to get a dynamo at the achievable magnetic Reynolds numbers, because the directly forced recirculation flow is too simple in structure and the evolving flow contributions beyond this velocity mode remain rather weak even close to resonance. Kinematic dynamo models based on hydrodynamic simulations and flow measurements at a down-scaled water precession experiment have confirmed that dynamo action is most likely in a small range of experimentally achievable parameters around the transition into a turbulent state. The project reported here deals with numerical and experimental studies that intend to derive essential features for the characterization of the flow state, to ensure that the desired flow structure will be adjustable in the experiment, and also to take measures to optimize this structure and the related amplitude to improve the conditions for a dynamo to occur. For this purpose, we follow a specific approach to improve the efficiency of the flow drive and to control the large-scale flow structures by mounting baffles on the inner side of the cylinder covers.
Projektbezogene Publikationen (Auswahl)
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Ekman boundary layers in a fluid filled precessing cylinder. AIP Advances, 11(3).
Pizzi, F.; Giesecke, A. & Stefani, F.
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Prograde and retrograde precession of a fluid-filled cylinder. New Journal of Physics, 23(12), 123016.
Pizzi, Federico; Giesecke, André; Šimkanin, Ján & Stefani, Frank
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Interplay between geostrophic vortices and inertial waves in precession-driven turbulence. Physics of Fluids, 34(12).
Pizzi, F.; Mamatsashvili, G.; Barker, A. J.; Giesecke, A. & Stefani, F.
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Numerical and theoretical framework for the DRESDYN precession dynamo experiment. Magnetohydrodynamics, 58(4), 445-454.
Pizzi, F.; Giesecke, A.; Šimkanin, J.; Kumar, V.; Gundrum, T. & Stefani, F.
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Numerical investigation of the flow inside a precession-driven cylindrical cavity with additional baffles using an immersed boundary method. Physics of Fluids, 34(9).
Wilbert, Mike; Giesecke, André & Grauer, Rainer
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Implementation and application of a pseudo-spectral MHD solver combined with an immersed boundary method to support the DRESDYN dynamo experiment. PhD diss., Bochum, Ruhr-Universität Bochum
M. Wilbert
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The effect of nutation angle on the flow inside a precessing cylinder and its dynamo action. Physics of Fluids, 35(1).
Kumar, Vivaswat; Pizzi, Federico; Giesecke, André; Šimkanin, Ján; Gundrum, Thomas; Ratajczak, Matthias & Stefani, Frank
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Special topic on precession, nutation, and libration driven flows. Physics of Fluids, 36(3).
Noir, Jérôme; Giesecke, André & Meunier, Patrice
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The global flow state in a precessing cylinder. Journal of Fluid Mechanics, 998.
Giesecke, André; Vogt, Tobias; Pizzi, Federico; Kumar, Vivaswat; Garcia, Gonzalez Fernando; Gundrum, Thomas & Stefani, Frank
