Intricate patterns of three-dimensional inertial wavebeams in a tilted librating cube

A fluid-filled cube rotating about an axis passing through the midpoints

of opposite edges is subjected to small librations (i.e. modulation of the

mean rotation). Low viscosity regimes, with Ekman number as small as

10^-8 are explored numerically. The full inertial range of forcing frequencies,

from 0 to twice the mean rotation rate are considered. The responses 

are dominated by inertial wavebeams emitted from edges and/or vertices,

depending on the forcing frequency. How these reflect on the cube's walls

and focus onto edges and vertices lead to intricate patterns which can be

reconciled using inviscid theory.