Abstract

Turbulence events in nature are often in the form of localized outbursts without a continuous source of energy; for example, in the atmosphere, patches of turbulence, or turbulent clouds, are created by local shear instabilities or internal gravity wave breaking. These events occur at scales of a few kilometers, and at this scale the flow is weakly influenced by the Earth’s rotation but strongly influenced by the stable density stratification, which motivates the study of decaying stratified turbulent clouds. Through experiments and numerical simulations we show that the edge dynamics of these clouds can be subdivided into fluid intrusions and predominantly horizontal internal gravity waves, whose propagation is due to the horizontal forcing of the intrusions. We present results from the DNS on the linearity and energetics of the waves, which demonstrate that the internal gravity waves transport up to ~15% of the energy away from the turbulent cloud. Finally, an attempt was made to perform an angular decomposition of the energetic contribution of the internal gravity waves, i.e. to determine whether the horizontal waveforms (as distinct from the more commonly observed inclined waves) dominate the energetics of the problem.