2023/02/27 by Falk Feddersen, Adam Fincham, Adam M. Fincham +9 · 1 citation
Earth and Planetary Sciences · #Coastal and Marine Dynamics #Ocean Waves and Remote Sensing #Aeolian processes and effects
paper · pdf · doi:10.1017/jfm.2023.40
The shape of depth-limited breaking-wave overturns is important for turbulence injection, bubble entrainment and sediment suspension. Overturning wave shape depends on a nonlinearity parameter H/h , where H is the wave height, and h is the water depth. Cross-shore wind direction (offshore/onshore) and magnitude affect laboratory shoaling wave shape and breakpoint location X_bp , but wind effects on overturning wave shape are largely unstudied. We perform field-scale experiments at the Surf Ranch wave basin with fixed bathymetry and ≈ 2.25 m shoaling solitons with small height variations propagating at C=6.7 \mathrm m \mathrm s-1 . Observed non-dimensional cross-wave wind Uw was onshore and offshore, varying realistically ( -1.2 < Uw/C < 0.7 ). Georectified images, a wave staff, and lidar are used to estimate X_bp , H/h , overturn area A and aspect ratio for 22 waves. The non-dimensionalized X_bp was inversely related to Uw/C . The non-dimensional overturn area and aspect ratio also were inversely related to Uw/C , with smaller and narrower overturns for increasing onshore wind. No overturning shape dependence on the weakly varying H/h was seen. The overturning shape variation was as large as prior laboratory experiments with strong H/h variations without wind. An idealized potential air flow simulation on steep shoaling soliton shape has strong surface pressure variations, potentially inducing overturning shape changes. Through wave-overturning impacts on turbulence and sediment suspension, coastal wind variations could be relevant for near-shore morphology.