  We investigated ram-pressure effects by an intracluster wind on an inner disk
of spiral galaxies by a hydrodynamical simulation. Even if the wind is mild and
not strong enough to strip the gas disk, the ram pressure disturbs orbits of
the inter-arm gas significantly. This results in asymmetric dense molecular
arms in the inner few kpc region of a galaxy. This mechanism would explain the
asymmetric CO gas distributions in the central regions often observed in Virgo
spirals.
