  The predictions of resolvent analysis for turbulent channel flow are
evaluated for a friction Reynolds number of Retau = 550. In addition to the
standard resolvent operator with kinematic viscosity, a resolvent operator
augmented with the Cess eddy viscosity is considered. Adding eddy viscosity
significantly alters the low-rank behavior of the resolvent. Regardless of the
wave speed selected, the eddy resolvent is low-rank for spanwise wavelengths of
ly+ = 80 and ly/h = 3.5 in comparison to the standard resolvent whose low-rank
behavior depends on the wave speed. The leading eddy modes have higher
projections onto the leading mode from spectral proper orthogonal decomposition
in comparison to standard resolvent modes. Neither analysis, however, reliably
predicts the most energetic wave speed. The standard resolvent tends to
overestimate it while the eddy resolvent underestimates it. When the most
energetic wave speed is underestimated, the eddy modes are energetic too close
to the wall. The eddy resolvent does, however, correctly identify the most
energetic wave speed and mode shapes for structures associated with the
near-wall cycle or that are most energetic at z/h = 0.5. These structures are
likely to be correctly predicted for any friction Reynolds number due to the
scaling of the Cess eddy viscosity profile. Finally, it is shown that the
accuracy of eddy predictions relies on the right balance between positive and
negative energy transfers. Even though eddy viscosity primarily adds
dissipation, its wall-normal gradient injects energy in the near-wall region,
resulting in mode shapes that are attached to the wall. For some scales the
predicted positive energy transfer is too strong thus biasing structures
towards the wall. The ability of the Cess eddy viscosity profile to model both
positive and negative energy transfers suggests that it could be optimized for
individual scales.
