Alignment of tracer gradient vectors in 2D turbulence

Autor: Guillaume Lapeyre, Patrice Klein, Bach Lien Hua
Přispěvatelé: Laboratoire de physique des océans (LPO), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École des Ponts ParisTech (ENPC)-École polytechnique (X)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)
Rok vydání: 2000
Předmět:
Zdroj: Physica D: Nonlinear Phenomena
Physica D: Nonlinear Phenomena, 2000, 146 (1-4), pp.246-260. ⟨10.1016/S0167-2789(00)00119-6⟩
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Physica D: Nonlinear Phenomena, Elsevier, 2000, 146 (1-4), pp.246-260. ⟨10.1016/S0167-2789(00)00119-6⟩
ISSN: 0167-2789
DOI: 10.1016/s0167-2789(00)00119-6
Popis: International audience; This numerical study examines the stirring properties of a 2D flow field with a specific focus on the alignment dynamics of tracer gradient vectors. In accordance with the study of Hua and Klein [Physica D 113 (1998) 98], our approach involves the full second order Lagrangian dynamics and in particular the second order in time equation for the tracer gradient norm. If the physical space is partitioned into strain-dominated regions and “effective” rotation-dominated regions (following a criterion defined by Lapeyre et al. [Phys. Fluids 11 (1999) 3729]), the new result of this study concerns the “effective” rotation-dominated regions: it is found, from numerical simulations of 2D turbulence, that the tracer gradient vector statistically aligns with one of the eigenvector of a tensor that comes out from the second order equation and is related to the pressure Hessian. The consequence is that, in those regions, the observed exponential growth or decay of the tracer gradient vector can be predicted contrary to previous results which implied zero growth and only a rotation of this vector. This result strongly emphasizes the important role of the time evolution of the strain rate amplitude which, with the rotation of the strain tensor, significantly contributes to the alignment dynamics. Both effects are related to the anisotropic part of the pressure Hessian, which emphasizes the non-locality of the mechanisms involved. These results are reminiscent of those recently obtained by Nomura and Post [J. Fluid Mech. 377 (1998) 65] for 3D turbulence.
Databáze: OpenAIRE
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