Resonances of a rotating black hole analogue

Understand

Under certain conditions, sound waves in a fluid may be governed by a Klein-Gordon equation on an `effective spacetime' determined by the background flow properties.

• Here we consider the draining bathtub: a circulating, draining flow whose effective spacetime shares key features with the rotating black hole (Kerr) spacetime.
• We present a complete investigation of the role of quasinormal (QN) mode and Regge pole (RP) resonances of this system.
• First, we simulate a perturbation in the time domain by applying a finite-difference method, to demonstrate the ubiquity of `QN ringing'.