The Nature of Turbulence

Coordinators: Eberhard Bodenschatz, Gregory Falkovich, Susan Kurien, Katepalli Raju Sreenivasan

Advances in key issues such as energy generation, pollution mitigation, and climate change, as well as progress in several fields of fundamental science from astrophysics to geophysics, are limited by the lack of understanding of the physics of turbulence.  Moreover, turbulence by itself presents one of the central fundamental problems of physics, that of a unified description of systems with many strongly interacting degrees of freedom that are in far-from-equilibrium states.

Progress has been difficult. In 2001 John Lumley and Akiva Yaglom surmised in their millennium review*: “We have very few great hypotheses…. Most of our experiments are exploratory experiments. What does this mean? We believe it means that, even after 100 years, turbulence studies are still in their infancy.”

Now, ten years later, the investigation of turbulent and complex flows has seen a revolution. For the first time in history, it is now becoming possible to measure with high resolution from the largest to the smallest scales not only the spatial but also the temporal properties of highly turbulent flows. In addition, thanks to the ever-increasing computational power of the world’s most powerful computers, it is becoming possible to simulate turbulence at levels that reveal its universal features. Experimental and numerical progress allows going beyond homogeneous isotropic turbulence. Particularly striking developments are emerging in increasingly complex situations, like inertial particles, particle-laden, multiphase and complex fluid turbulence, and even quantum turbulence, where the quantization of vortices becomes important (super fluid turbulence). The field is moving into increasingly complex situations that include not only transport of a second phase, but also phase transitions. An example can be found in the small-scale dynamics of clouds. Recently, it has become apparent that large-scale structures emerge from the random turbulent motion – these condensation phenomena need yet to be understood

In this rapidly moving field, it is timely and very important for the community of mathematicians, theorists, and experimentalists from fluid mechanics, condensed matter physics, soft matter physics, geophysics, and astrophysics to meet, to discuss, to define, and to solve the main questions laying ahead of us.

The goal of this four-month program is to advance the theory and to get turbulence experimentalists, computational physicists, modelers and theoreticians to work on a synthesis of new data and emerging theories. There will be five focus weeks during the program devoted to different broad themes:

  1. bulk turbulence in simple and complex fluids and quantum turbulence
  2. astrophysical turbulence
  3. buoyancy-driven turbulence and boundary layers
  4. turbulence and clouds, multiphase flows
  5. turbulence in geophysics.

*“A Century of Turbulence,” Applied Scientific Research (now Flow, Turbulence and Combustion) 66: 241–286, 2001.