  The pseudospectral method, in conjunction with a new technique for obtaining
scaling exponents $\zeta_n$ from the structure functions $S_n(r)$, is presented
as an alternative to the extended self-similarity (ESS) method and the use of
generalized structure functions. We propose plotting the ratio
$|S_n(r)/S_3(r)|$ against the separation $r$ in accordance with a standard
technique for analysing experimental data. This method differs from the ESS
technique, which plots $S_n(r)$ against $S_3(r)$, with the assumption $S_3(r)
\sim r$. Using our method for the particular case of $S_2(r)$ we obtain the new
result that the exponent $\zeta_2$ decreases as the Taylor-Reynolds number
increases, with $\zeta_2 \to 0.679 \pm 0.013$ as $R_{\lambda} \to \infty$. This
supports the idea of finite-viscosity corrections to the K41 prediction for
$S_2$, and is the opposite of the result obtained by ESS. The pseudospectral
method also permits the forcing to be taken into account exactly through the
calculation of the energy input in real space from the work spectrum of the
stirring forces.

Fluid Dynamics