A DEMONSTRATION OF THE SUPPRESSION OF TURBULENT CASCADES BY COHERENT VORTICES IN 2-DIMENSIONAL TURBULENCE

The role of coherent vortices in suppressing the rates of cascade (i.e., spectrum evolution through scale transfer and dissipation) is demonstrated in numerical solutions of decaying two-dimensional turbulence at high Reynolds number. The demonstration is made by comparing the evolution of a primary solution that has well-developed vortices with other solutions that initially have equivalent wavenumber spectra but lack vortices because of an imposed phase scrambling. The solutions without vortices have substantially greater cascade rates. Furthermore, when the primary solution is compared with other solutions whose initial conditions are constructed only from isolated, axisymmetric vortices, their spectrum evolution is qualitatively similar. This demonstrates the control of cascade rates by coherent vortices. © 1990 American Institute of Physics.