  The effect of grid resolution on large eddy simulation (LES) of wall-bounded
turbulent flow is investigated. A channel flow simulation campaign involving
systematic variation of the streamwise ($\Delta x$) and spanwise ($\Delta z$)
grid resolution is used for this purpose. The main friction-velocity based
Reynolds number investigated is 300. Near the walls, the grid cell size is
determined by the frictional scaling, $\Delta x^+$ and $\Delta z^+$, and
strongly anisotropic cells, with first $\Delta y^+ \sim 1$, thus aiming for
wall-resolving LES. Results are compared to direct numerical simulations (DNS)
and several quality measures are investigated, including the error in the
predicted mean friction velocity and the error in cross-channel profiles of
flow statistics. To reduce the total number of channel flow simulations,
techniques from the framework of uncertainty quantification (UQ) are employed.
In particular, generalized polynomial chaos expansion (gPCE) is used to create
meta models for the errors over the allowed parameter ranges. The differing
behavior of the different quality measures is demonstrated and analyzed. It is
shown that friction velocity, and profiles of velocity and the Reynolds stress
tensor, are most sensitive to $\Delta z^+$, while the error in the turbulent
kinetic energy is mostly influenced by $\Delta x^+$. Recommendations for grid
resolution requirements are given, together with quantification of the
resulting predictive accuracy. The sensitivity of the results to subgrid-scale
(SGS) model and varying Reynolds number is also investigated. All simulations
are carried out with second-order accurate finite-volume based solver. The
choice of numerical methods and SGS model is expected to influence the
conclusions, but it is emphasized that the proposed methodology, involving
gPCE, can be applied to other modeling approaches as well.
