RESUMEN

When discussing numerical solutions of the Navier–Stokes equations, especially when turbulent flows are concerned, there are at least two questions that can be raised. What is meaningful to compute? How to determine the fidelity of the computed solution with respect to the true solution? This paper takes a step towards the answer of these questions for turbulent flows. We consider longtime averages of weak solutions of the Navier–Stokes equations, rather than strong solutions. We present error estimates for the time-averaged energy dissipation rate, drag and lift, most of them under the assumption of small Reynolds/generalized Grashof number. For shear flows, we address the question of fidelity of the computed solution with respect to the true solution, in view of Kolmogorov’s energy cascade theory.