2013/02/28 by Daniela Tordella, Tordella, Daniela, Luca Sitzia +3
Earth and Planetary Sciences · Engineering · Physics and Astronomy · #Aeolian processes and effects #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Fluid Dynamics and Turbulent Flows #Solar and Space Plasma Dynamics
paper · pdf · doi:10.48550/arxiv.1302.7147
openalex publication_date 2013/02/28 · openalex created_date 2022/10/06 · openalex updated_date 2026/07/28
Using a Navier-Stokes isotropic turbulent field numerically simulated\n(Biferale et al., Phys. Fluids (2005)), we show that the probability of having\na stretching-tilting larger than twice the local enstrophy is negligible. By\nusing an anisotropic filter in the Fourier space we analyze these survival\nstatistics when the large, the small inertial or the small inertial and\ndissipation scales are filtered out. The probability that the ratio (|\ω\n U|/|\ω|2) is higher than a given threshold is higher in the\nunfiltered isotropic field than in the fields where the large scales were\nfiltered out and is lower than in the fields were the small inertial and\ndissipative scales are filtered out. This is due to the suppression of compact\nstructures in the removed ranges. The partial removal of the background of\nfilaments and sheets does not have a first order effect on these statistics.\nThese results are discussed in the light of a hypothesized relation between\nvortical filaments, sheets and blobs. The study can be viewed as a test for\nthis idea and tries to highlight its limits. A qualitative relation in physical\nspace and in Fourier space can be supposed to exist for blobs only. That is for\nthe near isotropic structures which are sufficiently described by a single\nspatial scale and do not suffer from the disambiguation problem as filaments\nand sheets do. Information is also given on the filtering effect on the angles\nbetween the strain rate tensor eigenvectors and the vorticity: eigenvector 2\nreduces its alignment, while eigenvector 3 reduces its misalignment. All\nfilters increase the gap between the most extensional eigenvalue and the\nintermediate one and the gap between this last and the contractile eigenvalue.\nWhen the large scales are missing, eigenvalue modulus 1 and 3 become nearly\nequal, similar to the modulus of the related components of the enstrophy\nproduction.\n