Colloquium on October 29, 2012

Tomas Bohr, Technical University of Denmark

Spontaneous Symmetry Breaking on Fluid Surfaces

Spontaneous symmetry breaking plays a major role in almost all branches of physics. Free surface flows are easy to excite and strongly nonlinear and thus provide spectacular examples. We shall discuss the breaking of axial symmetry in two examples: (1) the circular hydraulic jump on a plane, smooth horisontal surface and (2) the "rotating polygons" formed in strongly swirling free surface flows. In both cases "corners" are spontaneously generated which leads to polygon-like states, but since the Reynolds numbers differ by around two orders of magnitude, the mechanism of instability is very different.