Reflections and focusing of inertial waves 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 mean rotation). Low viscosity regimes, with Ekman number as $10^{-8}$ and equally relative forcing amplitude, are explored numerically. The full inertial range frequencies, from 0 twice rotation rate considered. response flows dominated by wavebeams emitted and/or vertices, depending on frequency. How these reflect cube's walls focus onto vertices lead intricate patterns. Most results can be reconciled using linear inviscid ray-tracing theory careful attention wavebeam emissions reflections. However, even at low amplitude considered, other effects discernible which not captured ray tracing. These include a symmetry breaking due viscous progressive wave, retrograde localized in boundary layers cube, nonlinear librational forcing.