Rare event-triggered transitions in aerodynamic bifurcation

TL;DR

This paper investigates rare-event-induced transitions in a bistable aerodynamic system, revealing that vortex shedding fluctuations control spontaneous state changes and analyzing their statistical properties.

Contribution

It introduces an experimental analysis of rare events in aerodynamic bistability, linking vortex shedding to transition dynamics and applying a rare-event statistical framework.

Findings

Waiting times follow a double-exponential distribution.

Transitions are driven by vortex shedding-induced fluctuations.

Spontaneous transitions span four orders of magnitude in time.

Abstract

The transitions between two states of a bistable system are investigated experimentally and analyzed in the framework of rare-event statistics. Considering a disk pendulum swept by a flow in a wind tunnel, bistability between two aerodynamic branches is observed, with spontaneous transitions from one branch to the other. The waiting times before spontaneous transition are distributed following a double-exponential as a function of the control parameter, spanning four orders of magnitude in time, for both transitions. Inspired by a model originally applied to the transition to turbulence, we show that, for the disk pendulum, both transitions are controlled by rare events of the aerodynamic forces acting on the disk which we propose to link in particular to the vortex shedding-induced fluctuations. Beyond the aerodynamic aspects, this work has interesting fundamental outcomes regarding the broad field of rare events in out-of-equilibrium systems.