Fourier Decomposition and Anisotropic Diffusion Filtering of Forced Turbulence

The Fourier decomposition and the anisotropic diffusion filtering model are used to extract various flow field scales and their coherent and incoherent parts. The different flow field scales are identified using the Fourier decomposition. Three cutoff wavenumbers are chosen to extract large, medium and fine scale velocity fields, respectively. Then, the anisotropic diffusion model is applied against the obtained velocity fields for each scale to define the coherent and incoherent parts. The forced turbulent velocities are simulated using the lattice Boltzmann method with resolutions 1283 and 2563, respectively. The Fourier decomposition of the velocity fields make the filtering process very difficult, so the anisotropic diffusion parameters should be chosen carefully to overcome the problems arising from the sharp cutoffs process. Although of such difficulties, results show that the anisotropic diffusion model successfully isolate the incoherent parts for each scale. It is shown that the incoherent parts ...