Oberseminar Numerische Mathematik / Scientific Computing
Charles Meneveau
Johns Hopkins University, Baltimore
Lagrangian dynamics of turbulence: models and synthesis
Abstract:
Recent theoretical and numerical results on intermittency in hydrodynamic turbulence are described, with special emphasis on the Lagrangian evolution. First, we derive the advected delta-vee system. This simple dynamical system deals with the Lagrangian evolution of two-point velocity and scalar increments in turbulence and shows how many known trends in turbulence can be simply understood from the proposed projection of the self-stretching effect coming from the nonlinear advective term. More detailed statistical information can be obtained from a model for the full velocity gradient tensor that uses a closure for the pressure Hessian and viscous terms. We will also describe efforts to use these insights in the generation of synthetic, multi-scale 3D vector fields with non-Gaussian statistics that reproduce many of know behavior of turbulence. Finally, the new insights obtained from this Lagrangian view of turbulence lead us directly to a new closure for the turbulence stresses based on matrix exponentials. The matrix-exponential closure is discussed in light of the stress transport equation and initial tests in Large Eddy Simulation of isotropic turbulence are presented.
| Datum: | Montag, 02.07.07 | Zeit: | 17:00 Uhr | Ort: | FU Berlin, Institut für Mathematik II, Arnimallee 6, 14195 Berlin. | Raum: | 032 im Erdgeschoss |