Disentangling inertial waves from eddy turbulence in a forced rotating turbulence experiment

etc15 Tracking Number 178

We present a spatio-temporal analysis of a statistically stationary rotating turbulence experiment, aiming to extract a signature of inertial waves and to determine at what scales and frequencies they can be detected. This analysis is performed from two-point correlations of temporal Fourier transform of the velocity fields obtained from time-resolved stereoscopic particle image velocimetry measurements in the rotating frame. We quantify the degree of anisotropy of turbulence as a function of frequency and spatial scale normal to the rotation axis. We show that this space-time-dependent anisotropy is well described by the dispersion relation of linear inertial waves at large scale, while smaller scales are dominated by the nonlinear sweeping of the waves by the random motions at larger scales. This sweeping effect is dominated here by the low-frequency quasi-two-dimensional component of the turbulence, a prominent feature of our experiment which is not accounted for by the weak wave turbulence theory.