Abstract
We present in situ observations of near‐bed velocity profiles with high
temporal and spatial resolution from a Nortek Vectrino Profiler deployed
in South San Francisco Bay. Using Hilbert analysis, we ensemble‐averaged
near‐bed velocity profiles by wave phase and calculated wave
phase‐dependent boundary layer thickness for varying wave and current
conditions. We also applied mixing length relationships to derive a
boundary layer thickness‐based eddy‐viscosity and compared this estimate
to one obtained from the k–ɛ turbulence model. From the eddy viscosity
estimates, we find that while turbulence responds instantaneously to
shear, boundary layer thickness lags by a scaling estimate based on the
turbulence response timescale. This analysis provides a method for
wave‐phase decomposition of field‐based velocity profile time series and
shows that there is a finite‐time response between turbulence
dissipation and boundary layer thickness.