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1. Comparing methods of modeling depth-induced breaking of irregular waves with a fully nonlinear potential flow approach

Author

Simon, Bruno, Papoutsellis, Christos E., Benoit, Michel, and Yates, Marissa L.

Subjects
Physics - Atmospheric and Oceanic Physics
Abstract

The modeling of wave breaking dissipation in coastal areas is investigated with a fully nonlinear and dispersive wave model. The wave propagation model is based on potential flow theory, which initially assumes non-overturning waves. Including the impacts of wave breaking dissipation is however possible by implementing a wave breaking initiation criterion and dissipation mechanism. Three criteria from the literature, including a geometric, kinematic, and dynamic-type criterion, are tested to determine the optimal criterion predicting the onset of wave breaking. Three wave breaking energy dissipation methods are also tested: the first two are based on the analogy of a breaking wave with a hydraulic jump, and the third one applies an eddy viscosity dissipative term. Numerical simulations are performed using combinations of the three breaking onset criteria and three dissipation methods. The simulation results are compared to observations from four laboratory experiments of regular and irregular waves breaking over a submerged bar, irregular waves breaking on a beach, and irregular waves breaking over a submerged slope. The different breaking approaches provide similar results after proper calibration. The wave transformation observed in the experiments is reproduced well, with better results for the case of regular waves than irregular waves. Moreover, the wave statistics and wave spectra are predicted well in general, and in particular for regular waves. Some differences are observed for irregular wave cases, in particular in the low-frequency range. This is attributed to incomplete absorption of the long waves in the numerical model. Otherwise, the wave spectra in the range $[0.5f_p,\: 5f_p]$ are reproduced well, before, inside, and after the breaking zone for the three irregular wave experiments., Comment: 25 pages, 14 figures, 5 tables. J. Ocean Eng. Mar. Energy (2019)

Published
2019
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3. Modeling of depth-induced wave breaking in a fully nonlinear free-surface potential flow model

Author

Papoutsellis, Christos E., Yates, Marissa L., Simon, Bruno, and Benoit, Michel

Subjects
Physics - Fluid Dynamics
Abstract

Two methods to treat wave breaking in the framework of the Hamiltonian formulation of free-surface potential flow are presented, tested, and validated. The first is an extension of Kennedy et al (2000)'s eddy-viscosity approach originally developed for Boussinesq-type wave models. In this approach, an extra term, constructed to conserve the horizontal momentum for waves propagating over a flat bottom, is added in the dynamic free-surface condition. In the second method, a pressure distribution is introduced at the free surface that dissipates wave energy by analogy to a hydraulic jump (Guignard and Grilli, 2001). The modified Hamiltonian systems are implemented using the Hamiltonian Coupled-Mode Theory, in which the velocity potential is represented by a rapidly convergent vertical series expansion. Wave energy dissipation and conservation of horizontal momentum are verified numerically. Comparisons with experimental measurements are presented for the propagation of a breaking dispersive shock wave following a dam break, and then incident regular waves breaking on a mildly sloping beach and over a submerged bar.

Published
2019
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7. Seasonal Sand Level Changes on Southern California Beaches

Author

Yates, Marissa L

Abstract

Seasonal airborne and ground-based observations of sand level changes were made along the coast of southern California from 2001 to 2008. Hourly, high alongshore spatial resolution wave estimates from a network of wave buoys and a spectral refraction wave model complement the sand level change data. Water returns from the ocean surface were removed from the airborne lidar elevation observations with a new method using tide and wave data, which was validated with concurrent in situ surveys. The resultant sand levels show high alongshore variability in seasonal shoreline position change along the 120-km survey region. Alongshore variability in wave energy, geologic factors, and sand grain size are hypothesized to control the alongshore variability of the seasonal shoreline change magnitude.Monthly or more frequent ground-based surveys at four selected focus sites show seasonal shoreline and bathymetry change, with winter shoreline erosion and offshore bar development, and summer shoreline accretion and the loss of the offshore bar. Analysis of surveys completed after a small beach nourishment at Torrey Pines Beach showed the presence of the nourishment through more than one full seasonal cycle.Observations from Torrey Pines Beach show the dependence of shoreline change on the initial shoreline position and the wave forcing. The observations motivated the development of an equilibrium shoreline change model, which accurately reproduces the observations with four free parameters. With at least two years of monthly surveys or multiple years of appropriately-timed biannual observations used to determine the free parameters, the model accurately predicts withheld observations and is applied at the additional survey sites. Ongoing work includes applying the model at additional locations and investigating the relationship between the tuned parameters and geologic factors.

Published
2009

10. Climate Change Impacts on Coastal Wave Dynamics at Vougot Beach, France

Author

Dissanayake, Pushpa, Yates, Marissa L., Suanez, Serge, Floc'H, France, Kramer, Knut, Dissanayake, Pushpa, Yates, Marissa L., Suanez, Serge, Floc'H, France, and Kramer, Knut

Abstract

Wave dynamics contribute significantly to coastal hazards and were thus investigated at Vougot Beach by simulating both historical and projected future waves considering climate change impacts. The historical period included a major storm event. This period was projected to the future using three globally averaged sea level rise (SLR) scenarios for 2100, and combined SLR and wave climate scenarios for A1B, A2, and B1 emissions paths of the IPCC. The B1 wave climate predicts an increase in the occurrence of storm events. The simulated waves in all scenarios showed larger relative changes at the beach than in the nearshore area. The maximum increase of wave energy for the combined SLR and wave scenarios was 95%, while only 50% for the SLR-only scenarios. The effective bed shear stress from waves and currents showed different spatial variability than that of the wave height, emphasizing the importance of interactions between nearshore waves and currents. Increases in the effective bed shear stress (combined scenarios: up to 190%, and SLR-only scenarios: 35%) indicate that the changes in waves and currents will likely have significant impacts on the nearshore sediment transport. This work emphasizes that combined SLR and future wave climate scenarios need to be used to evaluate future changes in local hydrodynamics and their impacts. These results provide preliminary insights into potential future wave dynamics at Vougot Beach under different climate change scenarios. Further studies are necessary to generalize the results by investigating the wave dynamics during storm events with different hydrodynamical conditions and to evaluate potential changes in sediment transport and morphological evolution due to climate change.

Published
2021
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11. Seasonal sand level changes on southern california beaches

Author

Yates, Marissa L.

Subjects
UCSD. Oceanography. (Discipline) Dissertations, Academic
Abstract

Seasonal airborne and ground-based observations of sand level changes were made along the coast of southern California from 2001 to 2008. Hourly, high alongshore spatial resolution wave estimates from a network of wave buoys and a spectral refraction wave model complement the sand level change data. Water returns from the ocean surface were removed from the airborne lidar elevation observations with a new method using tide and wave data, which was validated with concurrent in situ surveys. The resultant sand levels show high alongshore variability in seasonal shoreline position change along the 120-km survey region. Alongshore variability in wave energy, geologic factors, and sand grain size are hypothesized to control the alongshore variability of the seasonal shoreline change magnitude. Monthly or more frequent ground-based surveys at four selected focus sites show seasonal shoreline and bathymetry change, with winter shoreline erosion and offshore bar development, and summer shoreline accretion and the loss of the offshore bar. Analysis of surveys completed after a small beach nourishment at Torrey Pines Beach showed the presence of the nourishment through more than one full seasonal cycle. Observations from Torrey Pines Beach show the dependence of shoreline change on the initial shoreline position and the wave forcing. The observations motivated the development of an equilibrium shoreline change model, which accurately reproduces the observations with four free parameters. With at least two years of monthly surveys or multiple years of appropriately-timed biannual observations used to determine the free parameters, the model accurately predicts withheld observations and is applied at the additional survey sites. Ongoing work includes applying the model at additional locations and investigating the relationship between the tuned parameters and geologic factors

Published
2009

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