  We numerically study the inertial waves and zonal flows in spherical shells
driven by longitudinal libration, an oscillatory variation of rotation rate.
Internal shear layers are generated due to breakdown of the Ekman boundary
layer at critical latitudes. Our numerical results validate the scaling laws of
internal shear layers predicted by previous studies. Mean zonal flows are
driven by the non-linear interaction in the boundary layers. Non-linear
interaction of inertial waves in the interior fluids has no significant
contribution to the zonal flow. Multiple geostrophic shear layers are generated
due to non-linearities in the boundary layers at critical latitudes and
reflection points of internal shear layers. We also investigate the scaling
laws of geostrophic shear layers and extrapolate the results to the planetary
setting.
