  We present three-dimensional hydrodynamical simulations of buoyant gas in a
typical cluster environment. The hot matter was injected continuously into a
small region off-set from the cluster centre. In agreement with previous
analytic estimates we found that the bubbles evolve very differently depending
on their luminosity. Using tracer particles we computed radio maps of the
bubbles based on different assumptions about the magnetic field. In the radio
band the bubbles closely resemble FRI sources. For the bubbles to be detectable
for long enough to account for FRI sources, we found that reacceleration has to
take place. The bubbles are generally difficult to detect, both, in the radio
and in the X-ray band. Thus it is possible to hide a significant amount of
energy in the form of bubbles in clusters. Finally, we compute the efficiency
of the bubbles to stir the ICM and find that recurrent low-power sources may be
fairly effective in mixing the inner cluster region.
