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Physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach

Wave-by-wave and cumulative overtopping data from fixed planar impermeable smooth beaches will be presented from random wave experiments and compared with predictions from two nonlinear shallow water equations (NLSWE) models, Australian National University and Geoscience Australia (ANUGA) and Simula...

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Main Authors: Ibrahim, Muhammad Shazril Idris, Baldock, Tom E.
Format: Article
Published: American Society of Civil Engineers 2021
Subjects:
TA Engineering (General). Civil engineering (General)
Online Access:http://eprints.um.edu.my/27569/
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spelling my.um.eprints.275692022-06-09T06:46:12Z http://eprints.um.edu.my/27569/ Physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach Ibrahim, Muhammad Shazril Idris Baldock, Tom E. TA Engineering (General). Civil engineering (General) Wave-by-wave and cumulative overtopping data from fixed planar impermeable smooth beaches will be presented from random wave experiments and compared with predictions from two nonlinear shallow water equations (NLSWE) models, Australian National University and Geoscience Australia (ANUGA) and Simulating WAves till SHore (SWASH). These models have been tested and used by many researchers in various coastal processes studies. However, the capability of the models has not been tested when modeling wave-by-wave overtopping processes, and there is relatively limited validation for cumulative or time-averaged overtopping. The verified numerical models will be used to perform a parametric study on the relationship between overtopping and beach slope (beta), which has not been well resolved in the literature. This paper shows that the models provide reliable estimates of nearshore wave transformation and run-up, which includes the shoreline motion on a nontruncated beach, with SWASH modeling wave shoaling accurately. For the experimental configuration of a beach that was truncated with a sharp vertical edge, ANUGA provided more reliable estimates of wave-by-wave and cumulative overtopping and predicted total overtopping volumes without bias and within a few percent on the average overall. For wave-by-wave and cumulative overtopping SWASH is sensitive to the bathymetry at the overtopping edge, under predicting total overtopping volumes by approximately 25% for a sharp vertical edge but overpredicting by approximately 20% for a flat crest followed by a downward slope. A detailed investigation indicated that partial reflection occurred at the overtopping edge in the SWASH model for some configurations of the bathymetry, which lead to overestimated depths but reduced durations for positive discharge. The influence of beta on the ANUGA model run-up predictions and overtopping will be investigated and compared with empirical formulations. The ANUGA predictions for run-up were consistent with the empirical formulations for low beta and were linearly proportional to beta (tan beta), but were proportional to beta at a smaller power for a higher beta, which differed from the relationship given in some empirical models. For a given beach crest elevation (z(c)) with a sharp vertical edge and fixed wave conditions, the numerical ANUGA model and empirical model predictions for overtopping were approximately linearly proportional to tan beta, but the exact power varied depending on the chosen model. This was in contrast to some of the existing empirical models (when this dependency was explicit), but it was consistent with the analytical SWASH solution when written for positive volume flux (V-o) and deficit in the freeboard (R-z(c)) scaling. The numerical predictions from ANUGA agreed well with the empirical models. The modeling provided a new interpretation of the influence of the beta on overtopping in the empirical EurOtop formulation, where the complete influence of beta is not explicitly provided. (C) 2021 American Society of Civil Engineers. American Society of Civil Engineers 2021-09-01 Article PeerReviewed Ibrahim, Muhammad Shazril Idris and Baldock, Tom E. (2021) Physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach. Journal of Waterway, Port, Coastal, and Ocean Engineering, 147 (5). ISSN 0733-950X, DOI https://doi.org/10.1061/(ASCE)WW.1943-5460.0000663 <https://doi.org/10.1061/(ASCE)WW.1943-5460.0000663>. 10.1061/(ASCE)WW.1943-5460.0000663
institution Universiti Malaya
building UM Library
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Malaya
content_source UM Research Repository
url_provider http://eprints.um.edu.my/
topic TA Engineering (General). Civil engineering (General)
spellingShingle TA Engineering (General). Civil engineering (General)
Ibrahim, Muhammad Shazril Idris
Baldock, Tom E.
Physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach
description Wave-by-wave and cumulative overtopping data from fixed planar impermeable smooth beaches will be presented from random wave experiments and compared with predictions from two nonlinear shallow water equations (NLSWE) models, Australian National University and Geoscience Australia (ANUGA) and Simulating WAves till SHore (SWASH). These models have been tested and used by many researchers in various coastal processes studies. However, the capability of the models has not been tested when modeling wave-by-wave overtopping processes, and there is relatively limited validation for cumulative or time-averaged overtopping. The verified numerical models will be used to perform a parametric study on the relationship between overtopping and beach slope (beta), which has not been well resolved in the literature. This paper shows that the models provide reliable estimates of nearshore wave transformation and run-up, which includes the shoreline motion on a nontruncated beach, with SWASH modeling wave shoaling accurately. For the experimental configuration of a beach that was truncated with a sharp vertical edge, ANUGA provided more reliable estimates of wave-by-wave and cumulative overtopping and predicted total overtopping volumes without bias and within a few percent on the average overall. For wave-by-wave and cumulative overtopping SWASH is sensitive to the bathymetry at the overtopping edge, under predicting total overtopping volumes by approximately 25% for a sharp vertical edge but overpredicting by approximately 20% for a flat crest followed by a downward slope. A detailed investigation indicated that partial reflection occurred at the overtopping edge in the SWASH model for some configurations of the bathymetry, which lead to overestimated depths but reduced durations for positive discharge. The influence of beta on the ANUGA model run-up predictions and overtopping will be investigated and compared with empirical formulations. The ANUGA predictions for run-up were consistent with the empirical formulations for low beta and were linearly proportional to beta (tan beta), but were proportional to beta at a smaller power for a higher beta, which differed from the relationship given in some empirical models. For a given beach crest elevation (z(c)) with a sharp vertical edge and fixed wave conditions, the numerical ANUGA model and empirical model predictions for overtopping were approximately linearly proportional to tan beta, but the exact power varied depending on the chosen model. This was in contrast to some of the existing empirical models (when this dependency was explicit), but it was consistent with the analytical SWASH solution when written for positive volume flux (V-o) and deficit in the freeboard (R-z(c)) scaling. The numerical predictions from ANUGA agreed well with the empirical models. The modeling provided a new interpretation of the influence of the beta on overtopping in the empirical EurOtop formulation, where the complete influence of beta is not explicitly provided. (C) 2021 American Society of Civil Engineers.
format Article
author Ibrahim, Muhammad Shazril Idris
Baldock, Tom E.
author_facet Ibrahim, Muhammad Shazril Idris
Baldock, Tom E.
author_sort Ibrahim, Muhammad Shazril Idris
title Physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach
title_short Physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach
title_full Physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach
title_fullStr Physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach
title_full_unstemmed Physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach
title_sort physical and numerical modeling of wave-by-wave overtopping along a truncated plane beach
publisher American Society of Civil Engineers
publishDate 2021
url http://eprints.um.edu.my/27569/
_version_ 1735570292073299968
score 13.211869

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