Multipoint Turbulence Structure and Modelling

The idea of the SIG was launched by Julian Hunt, after the successful PEPIT/ERCOFTAC workshop held in Ecole Centrale de Lyon, May 9-12, 2000, "Two-point closures and their applications" (see Godeferd, Cambon & Scott, J. Fluid Mech., 436, 2001, 393-407).

"Two-point closures" (or TPC), however, is perhaps too restricted a topic, and the range of activities of this SIG will in fact cover various multi-scale, anisotropic and multi-modal aspects, possibly in connection with strong body forces and mean gradients. Inhomogeneity, especially induced by solid walls, will be addressed too.

In addition to classic TPC used in statistical theory, linear theory ("Rapid Distortion Theory" or RDT, stability analysis), weakly nonlinear theory (e.g. wave-turbulence), low-dimension dynamical models (e.g. using pod), shell-models, Lagrangian models for dispersion (e.g. using Kinematic Simulation, or KS, RDT, nonlinear TPC), have to be considered from a pragmatic view-point, in order, for instance, to suggest guidelines to improve simpler models (single-point closures in RANS, subgrid scale models for LES).

Use of symmetry groups (Lie group, SO(3) ), in agreement with both dynamical equations and boundary layers, is very promising. The SO(3) symmetry group and spherical harmonic expansions, which begin to be used in the "intermittency and scaling" community, have to be revisited in connection with fully anisotropic spectral description used for two decades in the team "Ondes et Turbulence", LMFA. The above list of tools is not exhaustive.

The SIG 35: "Multi-point Turbulence Structure and Modeling" is currently focused on the following topics:

• Two-point closures including detailed anisotropy
• Rapid distortion theory, WKB alternatives
• Multi-scale transfer of energy and anisotropy
• Lagrangian turbulence diffusion, from linear to non-linear models
• Multi-modal aspects for turbulence and interactions (Wave/Vortex ... etc)
• Subgrid scale models including effects of above listed aspects
• Advanced closures for RANS including structure based modeling
• Near-wall structures and modeling