  Systems of motile microorganisms exhibit a multitude of collective phenomena,
including motility-induced phase separation and turbulence. Sensing of the
environment and adaptation of movement plays an essential role in the emergent
behavior. We study the collective motion of wet self-steering polar
microswimmers, which align their propulsion direction hydrodynamically with
that of their neighbors, by mesoscale hydrodynamics simulations. The
simulations of the employed squirmer model reveal a distinct dependence on the
swimmer flow field, i.e., pullers versus pushers. The collective motion of
pushers is characterized by active turbulence, with nearly homogeneous density
and a Gaussian velocity distribution. Pullers exhibit a strong tendency for
clustering and display velocity and vorticity distributions with fat
exponential tails; their dynamics is chaotic, with a temporal appearance of
vortex rings and fluid jets. Our results show that the collective behavior of
intelligent microswimmers is very diverse and still offers many surprises to be
discovered.
