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Article

Dynamics of energy condensation in two-dimensional turbulence

Physical Review Letters. 2007. Vol. 99. P. 084501-1-084501-4.
Kolokolov I., Lebedev V., Chertkov M., Connaughton C.
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 k5=3 one. Once the coherent component is subtracted, however, the remaining fluctuations have a spectrum close to k1. The fluctuations decay slowly as the coherent part grows.