How a Whirlpool in a Cup Becomes a Black Hole Bomb ⚡ экспресс
Researchers studied the non-decaying Rankine vortex (a model with a rotating core) within the frameworks of shallow water and ideal fluid theories. At low circulation, instability is caused by the vorticity field, while at high circulation, when fluid is expelled, it is caused by a mechanism analogous to a 'black hole bomb' (reflected waves are endlessly amplified). A variational approach allowed separating the energy contributions of vortex and irrotational perturbations. Interestingly, such instability can create rotating polygons on the surface. Hollow vortices turned out to be the best terrestrial model for studying black holes.
When liquid is swirled in a cup, a vortex with an empty center forms. In this empty core, waves find a trap: bouncing off the walls, they siphon energy from the vortex and grow like a flame along a fuse — each wave stronger than the last, until a surge breaks loose.
The main surprise of the experiment: the best desktop analogue of a black hole turned out to be a vortex with a completely empty center. It is precisely the emptiness inside, like in a tornado, that makes its behavior almost cosmic. Thus, a simple pot of water becomes a portal to distant abysses.
🎯 Tornadoes and waterspouts exactly replicate the structure of black holes: their empty center acts as a trap for waves — once they reflect, an avalanche begins.