Characteristics of Wave Breaking and Blocking by Spatially Varying Opposing Currents

Abstract

A Reynolds‐Averaged Navier‐Stokes (RANS) flow solver with a Volume of Fluid (VOF) surface capturing scheme is used to investigate wave breaking and blocking due to strong opposing currents. The Shear Stress Transport (SST) k−ω model is modified in order to capture the turbulence properly. The unique capability of the RANS‐VOF model allows us to reveal the distinct features of current‐induced wave breaking and blocking. The limiting wave steepness at breaking onset is reduced considerably by the opposing current from the Stokes' limit for stationary waves. Although the wave height grows faster before breaking under a more rapidly varying current, the maximum height at the breaking onset remains almost the same. The locations of incipient breaking are slightly shifted downstream/upwave by the increased current gradient. It was found that the wave radiation stress alters the mean water level by competing with the pressure gradient arising from the current‐induced surface tilting. The wave set‐down and set‐up is more pronounced for more intensive breakers occurring under a larger incident wave and current gradient. Our model results indicate an undertow‐like change to the current profile due to wave breaking. The turbulence and vorticity generated by the current‐induced breaking wave persist and are advected downstream and interact with those generated by the following wave and current.

Variations in Wave Slope and Momentum Flux From Wave‐Current Interactions in the Tropical Trade Winds

“…Wave properties can vary on spatial scales by ones to tens of km (e.g., Branch et al., 2018; Thomson et al., 2014) or larger (e.g., Gemmrich & Pawlowicz, 2020), depending on the structure of coastal features associated with current variability, including river plumes (Branch et al., 2018; Thomson et al., 2014), fronts, and upwelling jets (Romero et al., 2017). Near river mouths, currents can even be strong enough to reduce the wave group velocity to zero and block the propagation of waves on the side of a front where currents strongly oppose the waves (Chawla & Kirby, 2002; Chen & Zou, 2018).…”

Wave Breaking Induced by Opposing Currents in Submerged Vegetation Canopies

“…Thus, the opposing currents can induce the observed higher WDV comparing to following currents. To our knowledge, the current‐induced wave breaking process has not yet been reported in WDV studies, but it has been well investigated in previous experiments without vegetation (Chawla & Kirby, 2002; Chen & Zou, 2018; Yu, 1952; Zheng et al., 2008). The mimic vegetation canopy in our experiments is similar to the elevated flume bed in previous studies, for example, Zheng et al.…”

“…Notably, most studies devote all the WDV to work done by vegetation drag force, whereas other possible wave dissipation mechanism is neglected. Previous studies without vegetation have found that opposing currents can induce partial wave breaking when the ratio between current velocity ( U ) and wave celerity ( c ) reaches certain thresholds (Brevik & Bjørn, 1979; Chen & Zou, 2018; Unna, 1942; Yu, 1952; Zheng et al., 2008). However, it is not clear if similar breaking process exists in vegetated fields with coexisting currents.…”

Wave-current interactions at the Tagus Estuary Mouth (Portugal) under storm wave conditions

“…Chawla and Kirby, 2002), phaseresolving models (e.g. Chen and Zou, 2018), or numerical modelling systems coupling a circulation model with a spectral wave model (e.g. Bertin et al, 2009;Olabarrieta et al, 2011;Dodet et al, 2013;Akan et al, 2017).…”