Vorticity in analogue gravity

Understand

In the analogue gravity framework, the acoustic disturbances in a moving fluid can be described by an equation of motion identical to a relativistic scalar massless field propagating in a curved spacetime.

• This description is possible only when the fluid under consideration is barotropic, inviscid and irrotational.
• In this case, the propagation of the perturbations is governed by an acoustic metric which depends algebrically on the local speed of sound, density and the background flow velocity, the latter assumed to be vorticity free.
• In this work we provide an straightforward extension in order to go beyond the irrotational constraint.