  We present the results of two-dimensional radiation-hydrodynamic simulations
of expanding supernova ejecta with a central energy source. As suggested in
previous multi-dimensional hydrodynamic simulations, a sufficiently powerful
central energy source can blow away the expanding supernova ejecta, leading to
efficient mixing of stratified layers in the ejecta. We assume that the energy
injection is realized in the form of non-thermal radiation from the wind nebula
embedded at the center of the ejecta. We found that the multi-dimensional
mixing in the ejecta assists the injected non-thermal radiation escaping from
the ejecta. When the non-thermal radiation is absorbed by the ejecta, it is
converted into bright thermal radiation or is consumed as the kinetic energy of
the supernova ejecta. We found that central energy sources with the injection
timescale similar to the photon diffusion timescale realize an efficient
conversion of the injected energy into thermal radiation. On the other hand, a
rapid energy injection ends up accelerating the ejecta rather than giving rise
to bright thermal emission. This remarkable difference potentially explains the
diversity of energetic supernovae including broad-lined Ic and superluminous
supernovae.
