Decay of grid turbulence in a finite channel

We develop a classical model for the decay of homogeneous and isotropic tur bulence that takes into account the growth of the energy containing length scale and its saturation when it reaches the size of the containing vessel. The model describes our data on the decay of grid turbulence in helium II through 4 orders of magnitude in vorticity, as well as classical experiment s on decaying turbulence.