  We propose a scenario in which a large fraction, or even most, of the gas
cooling to low temperatures of T<10^4 K in cooling flow clusters, directly
gains energy from the central black hole. Most of the cool gas is accelerated
to non-relativistic high velocities, v ~ 10^3-10^4 km/sec, after flowing
through, or close to, an accretion disk around the central black hole. A poorly
collimated wind (or double not-well collimated opposite jets) is formed.
According to the proposed scenario, this gas inflates some of the X-ray
deficient bubbles, such that the average gas temperature inside these bubbles
(cavities) in cooling flow clusters is kT_b ~< 100 keV. A large fraction of
these bubbles will be very faint, or not detectable, in the radio. The bright
rims of these weak smaller bubbles will appear as ripples. We suggest that the
X-ray ripples observed in the Perseus cluster, for example, are not sound
waves, but rather the rims of radio-faint weak bubbles which are only slightly
hotter than their environment. This scenario is incorporated into the moderate
cooling flow model; although not a necessary ingredient in that model, it
brings it to better agreement with observations. In the moderate cooling flow
model a cooling flow does exist, but the mass cooling rate is ~<10% of that in
old versions of cooling flow models.
