  We explore the direct modification of the pseudo-spectral truncation of 2D,
incompressible fluid dynamics to maintain a prescribed kinetic energy spectrum.
The method provides a means of simulating fluid states with defined spectral
properties, for the purpose of matching simulation statistics to given
information, arising from observations, theoretical prediction or high fidelity
simulation. In the scheme outlined here, Nos\'e-Hoover thermostats, commonly
used in molecular dynamics, are introduced as feedback controls applied to
energy shells of the Fourier-discretized Navier-Stokes equations. As we
demonstrate in numerical experiments, the dynamical properties (quantified
using autocorrelation functions) are only modestly perturbed by our device,
while ensemble dispersion is significantly enhanced in comparison with
simulations of a corresponding truncation incorporating hyperviscosity.
