Reducing the background anisotropy by using hexagonal Fourier transform in two-dimensional turbulent flows

J. Chai (1) , Le Fang (1) , Jean-Pierre Bertoglio (2)

1 LMP, Ecole Centrale de Pékin, Beihang University, Beijing 100191, China
2 LMFA - Laboratoire de Mecanique des Fluides et d'Acoustique

The two-dimensional hexagonal Fourier transform is introduced to reduce the background anisotropy in the numerical calculations with periodic conditions. Comparing to traditional Fourier transform with cartesian mesh, the large-scale background anisotropy is significantly reduced under different energy spectra.In addition, the phenomenon of small-scale background anisotropy is found to berelated to the type of low-pass filter. Considering the standard deviation of second order velocity correlation function with fixed two-point distance, the scaling at smallscales is a result of Taylor expansion, while the scaling at large scales can be explained by using a simplified single-wave number analytical model. The hexagonal Fourier transform can be easily implemented by using fast Fourier transform (FFT) libraries,and is expected to be applied in future pseudo-spectral methods of two-dimensional and quasi-three-dimensional turbulent flows to minimize the background anisotropy

Domaines: Mécanique des fluides [physics.class-ph]

J. Chai, Le Fang, Jean-Pierre Bertoglio. Reducing the background anisotropy by using hexagonal Fourier transform in two-dimensional turbulent flows. Computers and Fluids, 2020, 210, pp.104671. ⟨10.1016/j.compfluid.2020.104671⟩. ⟨hal-03234692⟩