Large-eddy simulation of a purely oscillating turbulent boundary layer

A numerical study of the Stokes boundary layer in the turbulent regime is performed and herein discussed in view of the relevant literature. The study is carried out by Large eddy simulations in conjunction with a plane-averaged dynamic mixed subgrid-scale model. As in canonical boundary layers, the grid resolution in the spanwise direction results critical to correctly reproduce the main characteristics of the flow. Specifically, resolved LES (according to the definition given for canonical wall-bounded flows) is proved to be able to reproduce correctly the main features of the flow field. Consistently with literature experimental studies, the presence of a log-layer was detected in the central phases of the oscillatory cycle, where turbulence is fully developed. At the value of Reynolds number herein investigated turbulence was observed to decay during the late deceleration and to switch on again in the mid acceleration phases. The analysis of the turbulence structure showed that the flow field resembles a canonical boundary layer in the phases of fully developed turbulence. In the remaining of the cycle, the vertical turbulent kinetic energy was found to decay and to re-energise much faster than the other two components, giving rise to an highly anisotropic behaviour.