Parameterization of nearshore wave front slope

Zhang, Chi; Zhang, Qingyang; Zheng, Jinhai; Demirbilek, Zeki

doi:10.1016/j.coastaleng.2017.06.008

Cited by 79 publications

(23 citation statements)

References 37 publications

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“…Although there is no other method to estimate the roller length to compare against, a quick estimation shows that for waves in about 6 m water depth, these roller lengths represent less than one-eight of the total wavelength, which is generally consistent with the front face extent of periodic saw-tooth waves (e.g., [38]). Although recently Zhang et al [39] presented a parameterization for the front slope angle, here θ is assumed fixed with a value of 15 • for both R1 and R2, consistent with the 2-24 • range reported in the literature from both laboratory and field experiments [13,23,24,26,[39][40][41]. In Figure 6, the mean roller length estimated using θ = 2 • and 24 • are also presented.…”

Section: Roller Lengths and Dissipation Fieldsmentioning

confidence: 54%

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Quantification of Two-Dimensional Wave Breaking Dissipation in the Surf Zone from Remote Sensing Data

2017

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A method for obtaining two dimensional fields of wave breaking energy dissipation in the surfzone is presented. The method relies on acquiring geometrical parameters of the wave roller from remote sensing data. These parameters are then coupled with a dissipation model to obtain time averaged two dimensional maps, but also the wave breaking energy dissipation on a wave-by-wave basis. Comparison of dissipation maps as obtained from the present technique and a results from a numerical model, show very good correlation in both structure and magnitude. The location of a rip current can also be observed from the field data. Though in the present work a combination of optical and microwave data is used, the underlying method is independent of the remote sensor platform. Therefore, it offers the possibility to acquire high quality and synoptic estimates that could contribute to the understanding of the surfzone hydrodynamics.

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Section: Roller Lengths and Dissipation Fieldsmentioning

confidence: 54%

“…Also, the model assumes the density of water for the roller density (cf. Equation 6 [39] for waves in the surfzone after the onset of breaking. In the future, it would be possible to include such parameterizations to further constrain the estimation.…”

Section: Sensitivity Analysismentioning

confidence: 99%

Quantification of Two-Dimensional Wave Breaking Dissipation in the Surf Zone from Remote Sensing Data

2017

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“…Table D1. In reality, Ur is usually less than 1,000 (e.g., Zhang et al, 2017). Therefore, we only provide the expression of f 3 for Ur up to 1,000.…”

Section: Discussionmentioning

confidence: 99%

Phase‐Averaged Drag Force of Nonlinear Waves Over Submerged and Through Emergent Vegetation

Zhu

Chen

2019

JGR Oceans

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Aquatic vegetation protects the shoreline by dissipating the wave energy and reducing the mean water level. For the latter, the phase‐averaged depth‐integrated drag force induced by vegetation ( trueFd‾) plays an essential role. For linear waves, the trueFd‾ exerted by submerged vegetation ( trueFdsub‾) and by the submerged part of emergent vegetation ( trueFdtrough‾) equal 0. As the wave nonlinearity increases, the profile of the horizontal velocity (u) becomes skewed and non–cosine shaped, and thus, both trueFdsub‾ and trueFdtrough‾ are nonzero (phase average of u|u|≠0) and their significance increases. This study examines the effects of wave nonlinearity and vegetation submergence on trueFd‾ based on stream function wave theory. In deep water, it is found that the wave nonlinearity slightly affects trueFdtrough‾ due to the negligible weight of trueFdtrough‾ in the overall trueFd‾. Both the wave nonlinearity and vegetation submergence have negligible effects on trueFdsub‾ as well. In shallow water, trueFdtrough‾ takes up a large percentage in the overall trueFd‾ for emergent vegetation, and a linear relationship between trueFdsub‾ and vegetation submergence exists for waves with relatively small wave heights. The applicable range of the linear wave theory based trueFd‾ is determined using trueFd‾ from stream function wave theory as a reference solution. Moreover, a parametric model is developed for evaluating trueFd‾ for random waves. The mean water level changes, or wave setup, on a vegetated sloping beach are validated and quantified using experimental data obtained from literature.

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“…An estuary is a place where a freshwater river meets the salty open-sea. The hydrodynamics in estuaries are very complex due to the presence of multi-scale physical processes, such as river discharge, tides, winds, waves and offshore currents [1][2][3]. The periodic mixing and stratification induced by the interaction of river discharge and tidal current plays an important role in mass transport and water quality in estuaries.…”

Section: Introductionmentioning

confidence: 99%

Kelvin-Helmholtz Billows Induced by Shear Instability along the North Passage of the Yangtze River Estuary, China

Shi

Tong

Zheng

et al. 2019

JMSE

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Kelvin-Helmholtz (K-H) instability plays a significant role in mixing. To investigate the existence of K-H instability along the North Passage of the Yangtze River Estuary, the non-hydrostatic model NHWAVE is utilized to simulate the fresh-salt water mixing process along the North Passage of the Yangtze River Estuary. Using high horizontal resolution, the structure of K-H billows have been successfully captured within the Lower Reach of the North Passage. The K-H instability occurs between the max flood and high-water slack. The duration and length scale of the K-H billows highly depends on the local interaction between fresh-water discharge and tide. The horizontal length scale of the instability is about 60 m, similar to the observations in other estuaries. In the vertical direction, the K-H billows exist within the pycnocline with length scale ranging from 6 to 7 m. The timescale of the billows is approximate 6 min. By analyzing the changes of potential energy during the mixing process, results show that the existence of K-H instability induces intense vertical mixing, which can greatly increase mixing efficiency in the North Passage of the Yangtze River Estuary.Miles [10] and Howard [11] showed that a necessary condition for K-H instability in a parallel, stratified, inviscid flow, is that the gradient Richardson number (Ri = N 2 /S 2 , where N = −(g/ρ)(∂ρ/∂z) is the Brunt-Väisälä frequency, S = du/dz is the velocity shear, g is the gravity acceleration, ρ is density and u is a representative flow speed) is less than 0.25 somewhere in the flow. However, it has been demonstrated this criterion is not sufficient [12], because it is possible to have a stable shear layer when Ri < 0.25 at the pycnocline. Fringer and Street [13] found the interfacial wave can be stable with Ri < 0.25, but unstable perturbations occurred when Ri < 0.13. Barad and Fringer [14] used an adaptive numerical method to evaluate the critical Ri for instability, and the result showed a similar value of Ri < 0.1 is required for instability. Based on laboratory experiments, Fructus et al. [15] proposed a new criterion for instability, which is L x /λ > 0.86, where L x is the length of the region with Ri < 0.25 and λ is the wave width. Another alternative criterion for instability is based on the linear stability analysis with the Taylor-Goldstein equation. Troy and Koseff [16] used the equation to derive the criterion for instability, which requiresσ i T w > 5, where T w is the time the fluid spends in region with Ri < 0.25 andσ i is the averaged growth rate of the instabilities in the region.

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Parameterization of nearshore wave front slope

Cited by 79 publications

References 37 publications

Quantification of Two-Dimensional Wave Breaking Dissipation in the Surf Zone from Remote Sensing Data

Quantification of Two-Dimensional Wave Breaking Dissipation in the Surf Zone from Remote Sensing Data

Phase‐Averaged Drag Force of Nonlinear Waves Over Submerged and Through Emergent Vegetation

Kelvin-Helmholtz Billows Induced by Shear Instability along the North Passage of the Yangtze River Estuary, China

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