Nonlocal interactions and condensation in forced rotating turbulence

Abstract

The Rossby number, $Ro = U/L2\Omega$, is the non-dimensional number characterizing rotating flows. Here U is the characteristic velocity, L the characteristic length scale, and $2\Omega$ is the Coriolis parameter. When Ro → 0 the nonlinearity of the equations of motion becomes weak, and the theories of weak wave interactions apply. The normal modes of the flow can be decomposed into zero-frequency 2D large scale structures and inertial waves (3D).

Rotating turbulent flow experiments and simulations are known to generate large-scale two-dimensional (2D) columnar structures from initially isotropic turbulence. Decaying turbulence simulations show this generation to be dependent on Rossby number, with three distinct regimes appearing [1]. These are the weakly rotating Ro regime, for which the turbulent flow is essentially unaffected by rotation, the intermediate Ro range, characterized by a strong transfer of energy from the wave to the 2D modes (with a peak at around Ro 0.2), and the small Ro range for which the 2D modes receive less and less energy from the wave modes as Ro → 0.