Abstract
We present 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 bin-averaged near-bed
velocity profiles by wave phase and calculated wave phase-dependent
boundary layer thickness for varying wave and current conditions and
discuss scaling relationships with flow characteristics. 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–ε
turbulence model. 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 the boundary layer thickness and eddy-viscosity adjust to
turbulence well within a wave period.