München 2019 – wissenschaftliches Programm

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EP: Fachverband Extraterrestrische Physik

EP 9: Poster

EP 9.21: Poster

Donnerstag, 21. März 2019, 16:30–19:00, Durchgangshalle

Statistical properties of material line elements in incompressible MHD turbulence — •Philipp Hess, Oliver Henze, and Wolf-Christian Müller — Technische Universität Berlin, Berlin, Germany

The statistics of infinitesimal material line elements are studied numerically in stationary incompressible magnetohydrodynamic (MHD) turbulence using velocity gradient time series. The velocity gradient data is obtained by tracking Lagrangian particles in a stochastically forced direct numerical simulation (DNS). The deformation of material lines in turbulence is of fundamental interest and practical importance. Vortex lines and magnetic field lines in an inviscid fluid of high conductivity are examples of vector fields that are proportional to material line elements. It is known analytically and shown in hydrodynamic simulations (Girimaji & Pope 1990) that the length of material line elements increases exponentially in time. The stretching rate of line and surface elements are found to be significantly lower in MHD turbulence than in the hydrodynamic case. Moreover the results show that the material lines are primarily aligned along the direction of the magnetic field. Further the role of the magnetic field in material element deformation is investigated by injecting cross and magnetic helicity into the system.