Higher-order and length-scale statistics from DNS of a decelerated planar wall-bounded turbulent flow

A DNS database is presented to document third- and fourth-order moments and their budgets for fully developed plane-channel flow and for strained plane-channel flow. The effect of straining has a similar effect on statistics, such as the skewness and flatness of velocities, as in an adverse-pressure-gradient (APG) boundary layer. In addition to higher-order statistics, some modeling implications are also described, including issues related to decomposition of the velocity-pressure gradient correlations, the assumption of dissipation isotropy and a fourth-order turbulence time scale. An analysis of two-point correlations along the inhomogeneous direction is made to include the effects of APG straining. This reveals the advantage of a one-point length-scale based on wall-normal velocity fluctuations as an alternative to the traditionally used length-scale based on turbulence kinetic energy. The present study should prove to be useful for turbulence modelers in need of data to develop and assess higher-than-second-order Reynolds-averaged Navier-Stokes closure models.