  We investigate the dynamical evolution of clusters of galaxies and their
observational consequences during off-center mergers, explicitly considering
the relaxation process between ions and electrons in intracluster medium by
N-body and hydrodynamical simulations. In the contracting phase a bow shock is
formed between the two subclusters. The observed temperature between two peaks
in this phase depends on the viewing angle even if the geometry of the system
seems to be very simple like head-on collisions. Around the most contracting
epoch, when we observe merging clusters nearly along the collision axis, they
look like spherical relaxed clusters with large temperature gradients. In the
expanding phase, spiral bow shocks occur. As in head-on mergers, the electron
temperature is significantly lower than the plasma mean one especially in the
post-shock regions in the expanding phase. When the systems have relatively
large angular momentum, double-peak structures in the X-ray images can survive
even after the most contracting epoch. Morphological features in both X-ray
images and electron temperature distribution characteristic to off-center
mergers are seriously affected by the viewing angle. When the clusters are
observed nearly along the collision axis, the distribution of galaxies'
line-of-sight (LOS) velocities is a good indicator of mergers. In the
contracting phase, an negative kurtosis and a large skewness are expected for
nearly equal mass collisions and rather different mass ones, respectively. To
obtain statistically significant results, about 1000 galaxies' LOS velocities
are required. For nearby clusters ($z<0.05$), large redshift surveys such as
2dF will enable us to study merger dynamics.
