S. Elsayed, R. Gijsman, T. Schlurmann, N. Goseberg
{"title":"Nonhydrostatic Numerical Modeling of Fixed and Mobile Barred Beaches: Limitations of Depth-Averaged Wave Resolving Models around Sandbars","authors":"S. Elsayed, R. Gijsman, T. Schlurmann, N. Goseberg","doi":"10.1061/(asce)ww.1943-5460.0000685","DOIUrl":null,"url":null,"abstract":": Along sandy coastlines, submerged, shore-parallel sandbars play an essential role in shoreline morphology by dissipating wave energy through depth-induced wave breaking. While wave breaking and sediment transport around sandbars are complex three-dimensional (3D) processes, shoreline morphology is typically simulated with depth-averaged models that feature lower computational demand than do 3D models. In this context, this study examines the implications of depth-averaging the fl ow fi eld and approximating the breaking process in nonhydrostatic models (e.g., XBeach nonhydrostatic) for the hydro-and morphodynamic processes around sandbars. The implications are drawn based on reproducing large-scale experiments of a barred beach pro fi le using the single-layer (XBNH) and the reduced two-layer (XBNH + ) modes of XBeach. While hydrodynamic processes were predicted with high accuracy on the sandbar ’ s seaward side, wave heights were overpredicted on the bar ’ s landward side. The overestimation was due to the simpli fi ed reproduction of the complex breaking process near the sandbar ’ s peak, particularly in terms of the generated turbulence in the water column. Moreover, the velocity pro fi le with a strong undertow could only be represented in a simpli fi ed way even using the two-layer mode XBNH + , thus resulting in inaccurate predictions of sediment loads around the sandbar. A parametric study is performed, and it revealed which model parameters control the simulation of the wave-breaking process. Thus, wave height predictions could be improved by tuning the energy-dissipation parameters. However, fl ow velocities and morphodynamic predictions could not be improved accordingly. Thus, this study identi fi es possible hydrodynamic model improvements, such as incorporating a roller dissipation model. Moreover, it improves understanding of key drivers and processes that should be included in nonhydrostatic depth-averaged models to simulate morphological changes around sandbars more ef fi ciently. DOI: 10.1061/(ASCE)WW.1943-5460.0000685 . This work is made available under the terms of the Creative Commons Attribution 4.0 International license, https://creativecommons.org/licenses/by/4.0/.","PeriodicalId":54367,"journal":{"name":"Journal of Waterway Port Coastal and Ocean Engineering","volume":null,"pages":null},"PeriodicalIF":1.4000,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"5","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Waterway Port Coastal and Ocean Engineering","FirstCategoryId":"5","ListUrlMain":"https://doi.org/10.1061/(asce)ww.1943-5460.0000685","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENGINEERING, CIVIL","Score":null,"Total":0}
引用次数: 5
Abstract
: Along sandy coastlines, submerged, shore-parallel sandbars play an essential role in shoreline morphology by dissipating wave energy through depth-induced wave breaking. While wave breaking and sediment transport around sandbars are complex three-dimensional (3D) processes, shoreline morphology is typically simulated with depth-averaged models that feature lower computational demand than do 3D models. In this context, this study examines the implications of depth-averaging the fl ow fi eld and approximating the breaking process in nonhydrostatic models (e.g., XBeach nonhydrostatic) for the hydro-and morphodynamic processes around sandbars. The implications are drawn based on reproducing large-scale experiments of a barred beach pro fi le using the single-layer (XBNH) and the reduced two-layer (XBNH + ) modes of XBeach. While hydrodynamic processes were predicted with high accuracy on the sandbar ’ s seaward side, wave heights were overpredicted on the bar ’ s landward side. The overestimation was due to the simpli fi ed reproduction of the complex breaking process near the sandbar ’ s peak, particularly in terms of the generated turbulence in the water column. Moreover, the velocity pro fi le with a strong undertow could only be represented in a simpli fi ed way even using the two-layer mode XBNH + , thus resulting in inaccurate predictions of sediment loads around the sandbar. A parametric study is performed, and it revealed which model parameters control the simulation of the wave-breaking process. Thus, wave height predictions could be improved by tuning the energy-dissipation parameters. However, fl ow velocities and morphodynamic predictions could not be improved accordingly. Thus, this study identi fi es possible hydrodynamic model improvements, such as incorporating a roller dissipation model. Moreover, it improves understanding of key drivers and processes that should be included in nonhydrostatic depth-averaged models to simulate morphological changes around sandbars more ef fi ciently. DOI: 10.1061/(ASCE)WW.1943-5460.0000685 . This work is made available under the terms of the Creative Commons Attribution 4.0 International license, https://creativecommons.org/licenses/by/4.0/.
期刊介绍:
The Journal of Waterway, Port, Coastal, and Ocean Engineering disseminates to the profession engineering and scientific advances made in the COPRI disciplines. The journal is a strong forum for civil engineering disciplines related to ocean, coastal and riverine waters as well as the interaction of these waters and the adjacent built and natural environments. This broad scope makes the Journal an ideal choice for the publication and dissemination of archival contributions dealing with important related topics. Topics include dredging, floods, sediment transport, tides, wind waves and storm surge, tsunamis, climate change, rising sea level, extreme weather events and other hazards that affect shorelines, waterways, estuaries, and ports and harbors, as well as efforts to mitigate the impact of such hazards. Of equal interest is the development and operation of offshore facilities and ocean resource utilization, such as renewable energy and ocean mining. Types of publications include original journal articles, comprehensive review articles, short technical notes, case studies of special interest to the readership, book reviews, and special issues on selected topics.