Existence and properties of the logarithmic layer in oscillating flows

The existence and properties of the logarithmic layer in a turbulent streamwise oscillating flow are investigated through direct numerical simulations and wall-resolved large-eddy simulations. The phase dependence of the von Kármán constant and the logarithmic layer intercept is explored for different values of the Reynolds number and the depth-ratio between the water depth and the Stokes boundary layer thickness. The logarithmic layer exists for a longer fraction of the oscillating period and a larger fraction of the water depth with increasing values of the Reynolds number. However, the values of both the von Kármán and the intercept depend on the phase, the Reynolds number and depth-ratio. Additionally, the simulations characterized by a low value of the depth-ratio and Reynolds number show intermittent existence of the logarithmic layer. Finally, the Reynolds number based on the friction velocity does not support a previously mentioned analogy between oscillatory flows and steady wall-bounded flows.