  In the current study, model expressions for fifth-order velocity moments
obtained from the truncated Gram-Charlier series expansions model for a
turbulent flow field probability density function are validated using data from
direct numerical simulation (DNS) of a planar turbulent flow in a strained
channel. Simplicity of the model expressions, the lack of unknown coefficients,
and their applicability to non-Gaussian turbulent flows make this approach
attractive to use for closing turbulent models based on the Reynolds-averaged
Navier-Stokes equations. The study confirms validity of the model expressions.
It also shows that the imposed flow deformation improves an agreement between
the model and DNS profiles for the fifth-order moments in the flow buffer zone
including when the flow reverses its direction. The study reveals sensitivity
of particularly odd velocity moments to the grid resolution. A new length scale
is proposed as a criterion for the grid generation near the wall and in the
other flow areas dominated by high mean velocity gradients when higher-order
statistics have to be collected from DNS.
