Scope

Scientific Scope and Topics

The basis for expecting the near-universal behaviour of small scales is Kolmogorov’s theory (1941 and 1962). The gaps in this theory are becoming increasingly certain. To establish a possible consensus of the new and post-Kolmogorov ideas, an Euromech Colloquium is being organized, to deal primarily with the non-universality of small scale dynamics. A manifestation of the non-universal behaviour of small-scales is closely related to small-scale anisotropy. This feature can be recast and presumably explained in different ways. For example:

  1. Local structure of turbulence from a kinematic point of view. It is interesting to detect the role of local velocity gradients, under the effect of strain and rotation. Particular attention must be paid to dissipation rate of the scalar variance, as well as to its local anisotropic behaviour.
  2. Statistical approach, when the small scales are explicitly linked to the turbulence forcing.
  3. Role played by coherent structures.
  4. Effects of rotation, stratification and such other body forces.

Turbulent flows are known to contain a wide range of scales, each range being characterized by its own physics. For instance, energy dissipation takes place at small-scales, yet the process is linked to the large scales of the system. One central problem of turbulence is to compute the large scale phenomena by modelling or parameterizing the small scales; this is the goal of sub-grid scale (SGS) models. Another example deals with modelling micromixing (relevant to chemical industry and combustion), in which small scales are the important feature. Laboratory and numerical results are continuously being generated on the small-scale features of turbulence dynamics. One fundamental question is: are the small scales universal? If so, under which conditions does this universality hold? If it does not hold, what are the circumstances? In particular, what is their connection to the large scale motion?

Audience

Interdisciplinary between physics (general physics, mathematics and statistics, earth and atmospheric sciences, astrophysics, plasma physics), and engineering (fluid dynamics, aerodynamics, environmental engineering, chemical engineering).