Where does flutter collide?

In aeroelasticity, flutter is a self-excited, potentially destructive oscillation of a structure in an airstream, in which aerodynamic, elastic, and inertial forces couple so that above a critical airspeed a small disturbance draws energy from the flow and grows instead of damping out. Bisplinghoff, Ashley, and Halfman's Aeroelasticity develops the conditions for the flutter boundary and the modal coupling, typically of bending and torsion, that drives it. The referent is a dynamic instability of a flexible structure in a fluid flow, defined by a flutter speed and frequency, and it is a different construct from a racing heart rhythm, sharing only the meaning of rapid trembling.[1]

Unit

The flutter speed and flutter frequency at the stability boundary

Recovery means

Not applicable

Measured by

Determined by flutter speed and frequency from wind-tunnel tests, flight flutter testing, and modal (V-g) analysis

In cardiology, flutter is a tachyarrhythmia, most often atrial flutter, in which a re-entrant electrical circuit drives the atria at a rapid, regular rate around 250–350 beats per minute, producing the characteristic sawtooth pattern on an electrocardiogram. Cosío's 2017 Atrial flutter, typical and atypical: a review describes the macro-re-entry circuits, usually around the tricuspid valve, and how they are mapped and ablated. The referent is a defined cardiac rhythm disorder characterised by its rate and circuit, and it has nothing to do with a wing shaking in flight, joined to it only by the shared word for a fast quiver.[2]

Unit

The atrial rate and the re-entrant circuit producing it

Recovery means

Can be interrupted by cardioversion or cured by catheter ablation of the re-entrant circuit

Measured by

Diagnosed by the electrocardiogram's sawtooth flutter waves and atrial rate, and mapped by intracardiac electrophysiology