Estimates of surf zone turbulence in a large-scale laboratory flume

Abstract

The details of a large-scale laboratory experiment to study the turbulence generated by waves breaking on a fixed barred beach are presented here. The data set includes comprehensive measurements of the free-surface and water particle velocity for one regular and one random wave case. Three methods were used to separate the wave-induced and turbulent components of velocity and are compared herein. Qualitatively, the cross-shore and vertical structure of the time-averaged turbulent intensity are independent of the method used. Inspection of the cross-shore variation of the turbulent intensity shows that the turbulence generated by wave breaking is largest at the bar crest and does not fully dissipate prior to reaching the bed, whereas landward of the bar, turbulence is generally confined to the upper layer. An analysis of the time variation of the turbulence and mass flux (to trough level) over the bar suggests that a strong correlation exists between intense wave breaking and the direction and magnitude of the mean flow averaged over several wave periods.