  We investigate the influence of ram pressure on the star-formation rate and
the distribution of gas and stellar matter in interacting model galaxies in
clusters. To simulate the baryonic and non-baryonic components of interacting
disc galaxies moving through a hot, thin medium we use a combined
N-body/hydrodynamic code GADGET2 with a description for star formation based on
density thresholds. Two identical model spiral galaxies on a collision
trajectory with three different configurations were investigated in detail. In
the first configuration the galaxies collide without the presence of an ambient
medium, in the second configurations the ram pressure acts face on on the
interacting galaxies and in the third configuration the ram pressure acts edge
on. The ambient medium is thin ($10^{-28}$ g/cm$^3$), hot (3 keV $\approx
3.6\times10^7$K) and has a relative velocity of 1000 km/s, to mimic an average
low ram pressure in the outskirts of galaxy clusters. The interaction
velocities are comparable to galaxy interactions in groups, falling along
filaments into galaxy clusters. The global star formation rate of the
interacting system is enhanced in the presence of ram pressure by a factor of
three in comparison to the same interaction without the presence of an ambient
medium. The tidal tails and the gaseous bridge of the interacting system are
almost completely destroyed by the ram pressure. The amount of gas in the wake
of the interacting system is $\sim50$% of the total gas of the colliding
galaxies after 500 Myr the galaxies start to feel the ram pressure. Nearly
$\sim10-15%$ in mass of all newly formed stars are formed in the wake of the
interacting system at distances larger than 20 kpc behind the stellar discs.
(abrigded)
