  Several energetic disturbances have been identified as triggers of the
large-amplitude oscillations (LAOs) in prominences. However, the mechanisms for
LAOs excitation are not well understood. We aim to study these mechanisms,
performing time-dependent numerical simulations in 2.5D and 2D setups using
magnetohydrodynamic (MHD) code MANCHA3D. Two types of disturbances are applied
to excite prominence oscillations, such as a perturbation associated with an
eruption and the waves caused by an artificial energy release. In the
simulation with the eruption, we obtain that it does not produce LAOs in the
prominence located in its vicinity. While the erupting flux rope rises, an
elongated current sheet forms behind it, which becomes unstable and breaks into
plasmoids. The downward-moving plasmoids cause perturbations in the velocity
field by merging with the post-reconnection loops. This velocity perturbation
propagates in the surroundings and perturbs the nearby prominence. The analysis
of the oscillatory motions of the prominence plasma reveals the excitation of
small-amplitude oscillations (SAOs), which are a mixture of longitudinal and
vertical oscillations. In the simulation with a distant artificial
perturbation, a fast-mode shock wave is produced, and it gradually reaches two
flux rope prominences at different distances. This shock wave excites vertical
LAOs and longitudinal SAOs with similar amplitudes, periods, and damping times
in both prominences. Finally, in the experiment with the external triggering of
LAOs in a dipped arcade prominence model, we find that, although the vector
normal to the front of a fast-mode shock wave is parallel to the spine of the
dipped arcade well before the contact, this wave does not excite longitudinal
LAOs. When the wave front approaches the prominence, it pushes the dense plasma
down, establishing vertical LAOs.
