TY - GEN A1 - Kupka, Friedrich A1 - Losch, Martin A1 - Zaussinger, Florian A1 - Zweigle, Thomas T1 - Semi-convection in the ocean and in stars: A multi-scale analysis T2 - Meteorologische zeitschrift N2 - Fluid stratified by gravitation can be subject to a number of instabilities which eventually lead to a flow that causes enhanced mixing and transport of heat. The special case where a destabilizing temperature gradient counteracts the action of a stabilizing gradient in molecular weight is of interest to astrophysics (inside stars and giant planets) and geophysics (lakes, oceans) as well as to some engineering applications. The detailed dynamics of such a system depend on the molecular diffusivities of heat, momentum, and solute as well as system parameters including the ratio of the two gradients to each other. Further important properties are the formation and merging of well-defined layers in the fluid which cannot be derived from linear stability analysis. Moreover, the physical processes operate on a vast range of length and time scales. This has made the case of semi-convection, where a mean temperature gradient destabilizes the stratification while at the same time the mean molecular gradient tends to stabilize it, a challenge to physical modelling and to numerical hydrodynamical simulation. During the MetStröm project the simulation codes ANTARES and MITgcm have been extended such that they can be used for the simulations of such flows. We present a comparison of effective diffusivities derived from direct numerical simulations. For both stars and the oceanic regimes, the Nusselt numbers (scaled diffusivities) follow similar relationships. Semi-convection quickly becomes inefficient, because the formation of layers limits vertical mixing. In contrast to the complementary saltfingering, these layers tend to damp instabilities so that effective diffusivities of salinity (concentration) are up to two orders of magnitudes smaller than in the former case. KW - hydrodynamics KW - numerical simulation KW - turbulence Y1 - 2015 UR - https://www.schweizerbart.de/papers/metz/detail/24/84729/Semi_convection_in_the_ocean_and_in_stars_A_multi_scale_analysis?l=DE U6 - https://doi.org/10.1127/metz/2015/0643 SN - 0941-2948 VL - 24 IS - 3 SP - 343 EP - 358 ER - TY - GEN A1 - Zaussinger, Florian A1 - Kupka, Friedrich A1 - Egbers, Christoph A1 - Neben, Matthias A1 - Hücker, S. A1 - Bahr, C. A1 - Schmitt, M. T1 - Semi-convective layer formation T2 - Journal of Physics: Conference Series Y1 - 2017 U6 - https://doi.org/10.1088/1742-6596/837/1/012012 VL - 837 IS - 1 ER - TY - GEN A1 - Zaussinger, Florian A1 - Kupka, Friedrich A1 - Montgomery, M. A1 - Egbers, Christoph T1 - Numerical simulation of DA white dwarf surface convection T2 - Journal of physics / Conference Series Y1 - 2018 U6 - https://doi.org/10.1088/1742-6596/1031/1/012013 SN - 1742-6596 SN - 1742-6588 VL - 1031 IS - 1 ER - TY - GEN A1 - Kupka, Friedrich A1 - Zaussinger, Florian A1 - Montgomery, M. H. T1 - Mixing and overshooting in surface convection zones of DA white dwarfs: First results from ANTARES T2 - Monthly Notices of the Royal Astronomical Society Y1 - 2018 SN - 1365-2966 SN - 0035-8711 VL - 474 IS - 4 SP - 4660 EP - 4671 ER - TY - GEN A1 - Grimm-Strele, Hannes A1 - Kupka, Friedrich A1 - Löw-Baselli, Bernhard A1 - Mundprecht, Eva A1 - Zaussinger, Florian A1 - Schiansky, Peter T1 - Realistic simulations of stellar surface convection with ANTARES: I. Boundary conditions and model relaxation T2 - New Astronomy Y1 - 2015 UR - http://www.sciencedirect.com/science/article/pii/S1384107613001383 U6 - https://doi.org/10.1016/j.newast.2013.11.005 SN - 1384-1076 VL - 34 SP - 278 EP - 293 ER -