New results are presented for the energy spectra of decaying 2D turbulence
in a square container with no-slip walls for integral-scale Reynolds number
s up to 20 000. The one-dimensional energy spectra measured close to the wa
lls reveal a k(-5/3) inertial range, instead of a k(-3) direct enstrophy ca
scade, due to the production of small-scale vorticity near no-slip boundari
es. During the intermediate decay stage a k(-3) spectrum starts to emerge a
nd the change in location of the injection scale of small-scale vorticity i
s explained in terms of an average boundary-layer thickness.