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In this paper we investigate the properties of rapidly rotating decayingturbulence using numerical simulations and phenomenological modelling. We findthat as the turbulent flow evolves in time, the Rossby number decreases to$\sim 10^{-3}$, and the flow becomes quasi-two-dimensional with strong coherentcolumnar structures arising due to the inverse cascade of energy. We establishthat a major fraction of energy is confined in Fourier modes $(\pm1,0,0)$ and$(0,\pm1,0)$ that correspond to the largest columnar structure in the flow. Forwavenumbers ($k$) greater than the enstrophy dissipation wavenumber ($k_d$),our phenomenological arguments and numerical study show that the enstrophy fluxand spectrum of a horizontal cross-section perpendicular to the axis ofrotation are given by $\epsilon_\omega\exp(-C(k/k_d)^2)$ and$C\epsilon_\omega^{2/3}k^{-1}\exp(-C(k/k_d)^2)$ respectively; for this 2D flow,$\epsilon_\omega$ is the enstrophy dissipation rate, and $C$ is a constant.Using these results, we propose a new form for the energy spectrum of rapidlyrotating decaying turbulence:$E(k)=C\epsilon_\omega^{2/3}k^{-3}\exp(-C(k/k_d)^2)$. This model of the energyspectrum is based on wavenumber-dependent enstrophy flux, and it deviatessignificantly from power law energy spectrum reported earlier.

Statistical features of rapidly rotating decaying turbulence: enstrophy and energy spectra, and coherent structures