Interaction of the inner and outer layers in large-eddy simulations with wall-layer models

We are applying approximate inner-layer treatments that allow large grid spacings in wall units in planes parallel to the wall, and thus extend Large-Eddy Simulation (LES) of wall-bounded flows to arbitrary Reynolds numbers. The interaction between the inner and outer layers, which are treated very differently, has led to two difficulties. First, hybrid RANS/LES methods such as DES with standard coefficients make the inner region much too smooth compared with the resolution of the grid. Second, as discovered by Nikitin et al. (2000), the velocity profile correctly returns a lower logarithmic layer dominated by the modeled Reynolds shear stress and an upper logarithmic layer dominated by the resolved stress; however, the two do not match well. There is a in the velocity "step" of several wall units. Modifications shown here largely correct the first problem, but the log-layer step is found to be very resistant.