Direct Measurement of Energy Transfer in Strongly Driven Rotating Turbulence.

Area of Science:

• Fluid dynamics
• Turbulence research
• Rotating fluid systems

Background:

• Understanding energy transfer in turbulent flows is crucial for many scientific and engineering applications.
• Rotating turbulent flows exhibit complex dynamics influenced by Coriolis forces.
• Previous studies on weakly driven turbulence offer limited insight into strongly driven systems.

Purpose of the Study:

• To investigate energy transfer mechanisms in strongly driven rotating turbulent flow.
• To probe the role of inertial waves in energy cascade processes.
• To compare observations with existing models of turbulence.

Main Methods:

• Introducing localized, abrupt increases in energy injection rate into a steady, strongly driven rotating turbulent flow.
• Analyzing the propagation of injected energy in real space, frequency domain, and wave number space.
• Utilizing spectral analysis to differentiate injected energy from the background turbulent flow.

Main Results:

• Injected energy propagates as a wave packet of inertial waves in real space.
• Energy is transferred nonlocally to low-frequency, quasigeostrophic modes in the frequency domain.
• Energy cascades locally towards smaller wave numbers, consistent with two-dimensional turbulence.
• An inverse energy cascade is unexpectedly mediated by inertial waves with small, non-zero frequencies.

Conclusions:

• Inertial waves play a significant role in energy transfer within strongly driven rotating turbulence.
• The observed energy transfer differs from predictions for weakly driven turbulence.
• These findings highlight the importance of inertial waves even near the two-dimensional manifold in rotating turbulent flows.