This paper reports on a computational study of the model error in the LANS-alpha
and NS-alpha deconvolution models of homogeneous isotropic turbulence. Computations are
also performed for a new turbulence model obtained as a rescaled limit of the deconvolution
model. The technique used is to plug a solution obtained from direct numerical simulation of
the incompressible Navier–Stokes equations into the competing turbulence models and to then
compute the time evolution of the resulting residual. All computations have been done in two
dimensions rather than three for convenience and efficiency. When the effective averaging length
scale in any of the models is α_{0} = 0.01 the time evolution of the root-mean-squared residual error
grows as √
t. This growth rate similar to what would happen if the model error were given by
a stochastic force. When α_{0 }= 0.20 the residual error grows linearly. Linear growth suggests
that the model error possesses a systematic bias. Finally, for α_{0} = 0.04 the residual error in
LANS-alpha model exhibited linear growth; however, for this value of α0 the higher-order alpha
models that were tested did not.