Several fascinating phenomena observed for 2D turbulence in bounded domains
are discussed. The first part of this paper concerns a short overview of t
he non-trivial behaviour of freely evolving 2D turbulence in square domains
with no-slip boundaries. In particular, the Reynolds number dependence of,
and the influence of the initial conditions on spontaneous spin-up of the
flow, which is characterised by a sudden increase of the absolute value of
the angular momentum of the flow, is investigated in more detail. In a seco
nd set-up we have investigated forced 2D turbulence in circular containers
with no-slip walls. A comparison with the double periodic case reveals that
domain-filling structures, always observed in the double periodic cases, a
re being prevented from emerging. Wall-generated, small-scale structures ar
e continuously injected into the interior of the domain, destroying larger
structures and maintaining the turbulent flow field. (C) 2001 Editions scie
ntifiques et medicales Elsevier SAS.