Recirculation in the lee of complicated headlands: A case study of Bass Point

It has been argued in recent papers that the nature of headland and coastal island wakes can be highly dependent on the level of turbulence caused by complicated coastal geometry and bottom topography, as well as on the loss of energy and momentum to the seabed due to friction. A series of field experiments was conducted around Bass Point (a 4‐km‐long headland near Sydney, Australia) using moored current meters and an acoustic Doppler current profiler. The offshore component of currents, measured offshore of the point, showed a high degree of spectral energy at about the 7‐day cycle, with a small amount at the diurnal frequency, but the reverse was found in the lee of the headland, where most of the recirculation was at the diurnal frequency. Numerical experiments resulted in similar spectra being obtained from locations behind the headland when the numerical model was forced with a spectrum of frequencies resembling the spectrum of the offshore free stream current, which was derived from the field results. The size and frequency of eddyshedding in the lee of the headland depended on the degree of variability of the inflowing free stream, with a diurnal component in the free stream appearing to cause the oscillations in the wake also of diurnal frequency. The numerical experiments also show that the size of the recirculating wake was affected by the complexity of the headland's geometry.