Supernova (SN) ejecta can be accelerated to attain relativistic speed by
energetic explosion. Spherically symmetric 1-dimensional simulations show
that the energy distribution of particles in SN ejecta follows a power law
(Fields et al. 2002, Nakamura & Shigeyama 2004). To investigate effects of
asphericity, we have constructed a 2-dimensional relativistic hydrodynamic
code using Piecewise Parabolic Method. Axi-symmetric explosion is initiated
by inserting kinetic energy biased in the polar direction. We find that the
energy distribution of matter accelerated by aspherical explosion does not
follow a simple power law. We also investigate the hydrodynamical
interaction between accelerated ejecta and circumstellar matter comparing
with a self-similar solution obtained for spherical explosion.