Influence of walls on transport and mixing in two-dimensional turbulence

Dr. Benjamin Kadoch, Laboratoire de Mécanique, Modélisation & Procédés Propres, M2P2-CNRS, Aix–Marseille Université and École Centrale Marseille, France

28 Apr 2011, 17:00; Location: S4|10-1

The influence of walls on the Lagrangian transport and mixing of passive scalars in turbulent two-dimensional flows is investigated. Two distinct geometries are considered by means of direct numerical simulation: a biperiodic domain and a circular domain with no-slip boundary conditions for velocity and zero flux for the scalar. A penalization method allows to take into account boundary conditions, in a classical pseudo-spectral code. This study shows that the creation of vorticity at the wall strongly influences the Lagrangian statistics. In particular, extreme values of Lagrangian acceleration appear in confined flows. The relationship between Lagrangian statistics and flow topology in fluid turbulence is also studied. The topology is characterized using the Weiss criterion, which provides a conceptually simple tool to partition the flow into topologically different regions: elliptic (vortex dominated), hyperbolic (deformation dominated), and intermediate (turbulent background). Moreover, the study of passive scalar showed that the mixing is more pronounced in the confined case than in the periodic case. Finally, the numerical methods used are then extended to the case of moving obstacles.

Category: CE Seminar


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