Multistability and memory effect in a highly turbulent flow: experimental evidence for a global bifurcation

Area of Science:

• Fluid Dynamics
• Turbulence Research
• Nonlinear Dynamics

Background:

• Von Kármán flow is a fundamental model for studying fluid dynamics.
• Understanding transitions in turbulent flows is crucial for many engineering applications.
• Previous studies have explored bifurcations in laminar flows, but less is known about highly turbulent regimes.

Purpose of the Study:

• To experimentally investigate the phenomenon of global bifurcation in a highly turbulent von Kármán flow.
• To characterize the transition dynamics and the role of turbulence in creating multiple flow solutions.
• To explore the memory effect in the flow and its relation to low-dimension dynamical systems.

Main Methods:

• Experimental setup for generating and measuring turbulent von Kármán flow.
• Analysis of mean flow properties to identify bifurcations.
• Statistical analysis of flow behavior during the transition.

Main Results:

• Experimental evidence of a global bifurcation in turbulent von Kármán flow.
• The canonical symmetric solution becomes unstable, leading to symmetry-breaking flow states even at high Reynolds numbers.
• The bifurcation is highly subcritical, indicating a flow memory effect.
• The transition exhibits peculiar statistics, similar to low-dimension dynamical systems.

Conclusions:

• Turbulence plays a dual role: enabling multiple hydrodynamical solutions and influencing the nature of transitions.
• The observed subcritical global bifurcation and flow memory have significant implications for understanding complex fluid systems.
• The findings bridge the gap between turbulent flow phenomena and low-dimension dynamical system theory.