Multiple states in highly turbulent Taylor-Couette flow

Area of Science:

• Fluid dynamics
• Turbulence theory
• Complex systems

Background:

• Turbulent flows are ubiquitous in nature and technology, necessitating fundamental understanding.
• Kolmogorov's 1941 paradigm posits a single turbulent state for high-dimensional, fluctuating systems.
• The existence of multiple states in high Reynolds number flows remains an open question.

Purpose of the Study:

• To investigate the existence of multiple turbulent states in Taylor-Couette flow.
• To test Kolmogorov's paradigm in the regime of ultimate turbulence.
• To explore the phase space of turbulent flow dynamics.

Main Methods:

• Experimental investigation of Taylor-Couette flow at high Reynolds numbers (Re = O(10^6)) and Taylor numbers (Ta = O(10^12)).
• Probing the phase space defined by the rotation rates of the inner and outer cylinders.
• Utilizing combined global torque and local velocity measurements.

Main Results:

• Conclusive evidence for multiple distinct turbulent states was observed.
• These states were identified within the ultimate turbulence regime.
• The findings demonstrate bifurcations in high-dimensional turbulent flows.

Conclusions:

• The study provides the first conclusive evidence of multiple turbulent states in high Reynolds number Taylor-Couette flow.
• This discovery challenges the long-standing Kolmogorov's 1941 paradigm for turbulence.
• The results indicate that complex fluid dynamics can exhibit multiple coexisting turbulent states.