Clustering of vector nulls in homogeneous isotropic turbulence

We analyze the vector nulls of velocity, Lagrangian acceleration, and vorticity, coming from direct numerical simulations of forced homogeneous isotropic turbulence at Re λ ∈ O([40 − 600]). We show that the clustering of velocity nulls is much stronger than those of acceleration and vorticity nulls....

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Bibliographic Details
Published in:Physical review fluids 2021-02, Vol.6 (2), Article 024609
Main Authors: Mora, D. O., Bourgoin, M., Mininni, P. D., Obligado, M.
Format: Article
Language:English
Subjects:
Engineering Sciences
Nonlinear Sciences
Physics
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Summary:We analyze the vector nulls of velocity, Lagrangian acceleration, and vorticity, coming from direct numerical simulations of forced homogeneous isotropic turbulence at Re λ ∈ O([40 − 600]). We show that the clustering of velocity nulls is much stronger than those of acceleration and vorticity nulls. These acceleration and vorticity nulls, however, are denser than the velocity nulls. We study the scaling of clusters of these null points with Re λ and with characteristic turbulence lengthscales. We also analyze datasets of point inertial particles with Stokes numbers St = 0.5, 3, and 6, at Re λ = 240. Inertial particles display preferential concentration with a degree of clustering that resembles some properties of the clustering of the Lagrangian acceleration nulls, in agreement with the proposed sweep-stick mechanism of clustering formation.
ISSN:2469-990X
2469-990X
DOI:10.1103/PhysRevFluids.6.024609