Publikationen
Jeremiah Lübke, Frederic Effenberger, Mike Wilbert, Horst Fichtner, Rainer GrauerTowards Synthetic Magnetic Turbulence with Coherent StructuresSynthetic turbulence is a relevant tool to study complex astrophysical and space plasma environments inaccessible by direct simulation. However, conventional models lack intermittent coherent structures, which are essential in realistic turbulence. We present a novel method, featuring coherent structures, conditional structure function scaling and fieldline curvature statistics comparable to magnetohydrodynamic turbulence. Enhanced transport of charged particles is investigated as well. This method presents significant progress towards physically faithful synthetic turbulence. submitted (2024) 
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Jan Friedrich, Mike Wilbert, Raffaele MarinoNonlocal Contributions to the Turbulent Cascade in Magnetohydrodynamic TurbulenceWe present theoretical and numerical evidence for nonlocal contributions to the turbulent energy cascade in magnetohydrodynamic (MHD) turbulence. Therefore, we revisit a well-known result derived directly from the MHD equations, i.e., the so-called Politano & Pouquet (P&P) law for the transfer of kinetic and magnetic energy in scale. We propose an additional nonlocal term that represents the influence of fluctuations from large scales due to the Alfvén effect. Furthermore, we discuss the implications of this additional nonlocal term for the cascade process in the context of the observed heating of the solar wind plasma. Supported by direct numerical simulations of homogeneous and isotropic MHD turbulence, we verify that neglecting the additional nonlocal term might consistently overestimate energy dissipation rates and, thus, the contributions of turbulent energy dissipation to solar wind heating. submitted (2023) 
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Mike Wilbert, André Giesecke, and Rainer GrauerNumerical Investigation of the Flow inside a Precession driven cylindrical Cavity with additional Baffles using an Immersed Boundary MethodIn this paper we present a numerical approach to solve the Navier-Stokes equations for arbitrary vessel geometries by combining a Fourier-Spectral method with a direct forcing Immersed Boundary method which allows to consider solid-fluid interactions. The approach is applied to a paradigmatic setup motivated by the precession dynamo experiment currently under construction at Helmholtz- Zentrum Dresden-Rossendorf (HZDR) are presented. The experiment consists of a fluid filled cylinder rotating about 2 axes which induces a precession driven flow inside the cavity. The cylinder is also equipped with baffles at the end caps with adjustable penetration depth to impact the flow. The numerical details as well as simulation results for the spin up and precession driven flow in a circular cylinder with additional baffles are presented. Phys. Fluids 34 (2022) 96607 
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