• dns
• turbulence
• homogeneous isotropic turbulence
• anisotropy
• nek5000
• isodns
• spectral methods
• pseudospectral methods
• spectral element method
• viscosity
• vortices
• anisotropy invariant maps
• autocorrelations
• Taylor microscales
• swirling strength

The effects of an anisotropic viscosity of the fluid on the characteristics of a turbulent flow are studied by performing direct numerical simulations of a three-dimensional periodic box of homogeneous turbulence. This work is correlated to an on-going experimental campaign conducted by the PhD candidate Hanna Berning at the institute of fluid dynamics of ETH Zürich. The anisotropy of the viscosity is introduced by using a ferrofluid subjected to an external magnetic field. The Ericksen-Leslie theory and the work of Ilg and Kröger has been used to model the viscosity using a stress tensor which involve 6 viscous coefficients. Since key turbulence quantities cannot be computed due to the lack of a scalar viscosity, new turbulence parameters are proposed and analyzed in order to investigate the flow. The simulations are performed using an extended version of the spectral element solver Nek5000 and the results matched the ones of a spectral code implemented and extended by the postdoctoral researcher Davide Gatti. It is shown how the anisotropy of the viscosity affected the energy content of the flow and the preferential direction of alignment of its vortical structures. The predominant effects were found at the smallest scales of motion but also the largest eddies were proved to be slightly influenced by the anisotropy introduced at the viscous scales.