Experimental Study of Energy Transfer by Inertial Waves During the Build up of Turbulence in a Rotating System

TL;DR

This study investigates how inertial waves transfer energy during the transition to turbulence in a rotating water system, revealing linear wave propagation and nonlinear energy transfer timescales that influence turbulence characteristics.

Contribution

It provides experimental evidence of inertial wave-mediated energy transfer and distinguishes linear and nonlinear timescales in rotating turbulence.

Findings

Energy is transported by inertial wave packets at linear wave speeds.

A clear energy front defines the linear energy transport timescale.

Nonlinear energy transfer occurs over longer timescales, affecting turbulence statistics.

Abstract

We study the transition from fluid at rest to turbulence in a rotating water cylinder. We show that the energy, injected at a given height, is transported by inertial wave packets through the fluid volume. These waves propagate at velocities consistent with those calculated from linearized theory, even when they possess large amplitudes. A clear "front" in the temporal evolution of the energy power spectrum is detected, defining a time scale for energy transport at the linear wave speed in the system. Nonlinear energy transfer between modes is governed by a different time scale that can be much longer than the linear one. These observations suggest that the energy distribution and statistics in rotating turbulent fields that are driven by intermittent energy sources may be different from those described by the inverse energy cascade in two-dimensional turbulence.