Abstract
We report a numerical study, supplemented by phenomenological explanations, of “energy condensation” in forced 2D turbulence in a biperiodic box. Condensation is a finite size effect which occurs after the standard inverse cascade reaches the size of the system. It leads to the emergence of a coherent vortex dipole. We show that the time growth of the dipole is self-similar, and it contains most of the injected energy, thus resulting in an energy spectrum which is markedly steeper than the standard one. Once the coherent component is subtracted, however, the remaining fluctuations have a spectrum close to . The fluctuations decay slowly as the coherent part grows.
- Received 9 January 2007
DOI:https://doi.org/10.1103/PhysRevLett.99.084501
©2007 American Physical Society