Rare Event-Triggered Transitions in Aerodynamic Bifurcation

Area of Science:

• Physics
• Fluid Dynamics
• Nonlinear Dynamics

Background:

• Bistable systems exhibit two stable states, with transitions between them being critical phenomena.
• Rare-event statistics provide a framework for analyzing infrequent but significant events in dynamic systems.
• Understanding transitions in fluid-driven systems is crucial for predicting complex behaviors.

Purpose of the Study:

• To experimentally investigate and statistically analyze the transitions between two aerodynamic states in a disk pendulum.
• To identify the underlying mechanisms controlling these spontaneous transitions.
• To connect the observed phenomena to the broader field of rare events in out-of-equilibrium systems.

Main Methods:

• Experimental setup involving a disk pendulum in a wind tunnel.
• Analysis of waiting times between spontaneous transitions using rare-event statistics.
• Comparison with models applied to transition phenomena, such as transition to turbulence.

Main Results:

• Bistability between two aerodynamic branches was observed in the disk pendulum.
• Waiting times for transitions followed a double exponential distribution, spanning four orders of magnitude.
• Transitions were shown to be controlled by rare aerodynamic force events, likely related to vortex shedding.

Conclusions:

• The study demonstrates that transitions in this fluid-driven bistable system are governed by rare aerodynamic events.
• The findings offer fundamental insights into rare events in out-of-equilibrium systems.
• This work highlights the applicability of rare-event statistics to fluid dynamics and mechanical systems.