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  • 1
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    Hydrodynamic and sediment transport modeling of New River Inlet (NC) under the interaction of tides and waves (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 120 (2015): 4028–4047, doi:10.1002/2014JC010425.
    Description: The interactions between waves, tidal currents, and bathymetry near New River Inlet, NC, USA are investigated to understand the effects on the resulting hydrodynamics and sediment transport. A quasi-3-D nearshore community model, NearCoM-TVD, is used in this integrated observational and modeling study. The model is validated with observations of waves and currents at 30 locations, including in a recently dredged navigation channel and a shallower channel, and on the ebb tidal delta, for a range of flow and offshore wave conditions during May 2012. In the channels, model skills for flow velocity and wave height are high. Near the ebb tidal delta, the model reproduces the observed rapid onshore (offshore) decay of wave heights (current velocities). Model results reveal that this sharp transition coincides with the location of the breaker zone over the ebb tidal delta, which is modulated by semidiurnal tides and by wave intensity. The modulation of wave heights is primarily owing to depth changes rather than direct wave-current interaction. The modeled tidally averaged residual flow patterns show that waves play an important role in generating vortices and landward-directed currents near the inlet entrance. Numerical experiments suggest that these flow patterns are associated with the channel-shoal bathymetry near the inlet, similar to the generation of rip currents. Consistent with other inlet studies, model results suggest that tidal currents drive sediment fluxes in the channels, but that sediment fluxes on the ebb tidal delta are driven primarily by waves.
    Description: Funding was provided by the Office of Naval Research (N00014-13-1–0120 and N00014-14-1-0586) and the Office of the Assistant Secretary of Defense for Research and Engineering.
    Description: 2015-12-07
    Keywords: Wave-current interaction ; Sediment transport ; New River ; Morphological evolution ; Tidal inlet
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Wave-induced sediment transport and onshore sandbar migration (2006)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Coastal Engineering 53 (2006): 817-824, doi:10.1016/j.coastaleng.2006.04.003.
    Description: The 25-m onshore migration of a nearshore sandbar observed over a 5-day period near Duck, NC is simulated with a simplified, computationally efficient, wave-resolving singlephase model. The modeled sediment transport is assumed to occur close to the seabed and to be in phase with the bottom stress. Neglected intergranular stresses and fluid-granular interactions, likely important in concentrated flow, are compensated for with an elevated (relative to that appropriate for a clear fluid) model roughness height that gives the best fit to the observed bar migration. Model results suggest that when mean-current-induced transport is small, wave-induced transport leads to the observed onshore bar migration. Based on the results from the simplified phase-resolving model, a wave-averaged, energetics-type model (e.g., only moments of the near-bottom velocity field are required) with different friction factors for oscillatory and mean flows is developed that also predicts the observed bar migration. Although the assumptions underlying the models differ, the similarity of model results precludes determination of the dominant mechanisms of sediment transport during onshore bar migration.
    Description: Supported by the Office of Naval Research, the National Science Foundation, the Army Research Office, and the Woods Hole Oceanographic Institution Coastal Ocean Institute.
    Keywords: Sediment transport ; Sandbar migration ; Wave boundary layer ; Roughness ; Bottom stress
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 3
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    Effects of wave shape on sheet flow sediment transport (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C05025, doi:10.1029/2003JC002075.
    Description: A two-phase model is implemented to study the effects of wave shape on the transport of coarse-grained sediment in the sheet flow regime. The model is based on balance equations for the average mass, momentum, and fluctuation energy for both the fluid and sediment phases. Model simulations indicate that the responses of the sheet flow, such as the velocity profiles, the instantaneous bed shear stress, the sediment flux, and the total amount of the mobilized sediment, cannot be fully parameterized by quasi-steady free-stream velocity and may be correlated with the magnitude of local horizontal pressure gradient (or free-stream acceleration). A net sediment flux in the direction of wave advance is obtained for both skewed and saw-tooth wave shapes typical of shoaled and breaking waves. The model further suggests that at critical values of the horizontal pressure gradient, there is a failure event within the bed that mobilizes more sediment into the mobile sheet and enhances the sediment flux. Preliminary attempts to parameterize the total bed shear stress and the total sediment flux appear promising.
    Description: We gratefully acknowledge the financial supports of the National Ocean Partnership Program and the Department of Civil and Environmental Engineering, University of Delaware.
    Keywords: Sediment transport ; Bed shear stress ; Sheet flow
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Toward modeling turbulent suspension of sand in the nearshore (2010)
    American Geophysical Union
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C06018, doi:10.1029/2003JC002240.
    Description: We present two depth- and phase-resolving models, based on single- and two-phase approaches for suspended sediment transport under water waves. Both models are the extension of a wave hydrodynamic model Cornell Breaking Wave and Structure (COBRAS). In the two-phase approach, dilute two-phase mass and momentum equations are calculated along with a fluid turbulence closure based on balance equations for the fluid turbulence kinetic energy k f and its dissipation rate ε f . In the single-phase approach the fluid flow is described by the Reynolds-Averaged Navier-Stokes equations, while the sediment concentration is calculated by an advection-diffusion equation for the conservation of sediment mass. The fluid turbulence is calculated by k f -ε f equations that incorporate the essential influence of sediment, which can also be consistently deduced from the two-phase theory. By adopting a commonly used sediment flux boundary condition near the bed the proposed models are tested against laboratory measurements of suspended sediment under nonbreaking skewed water waves and shoaling broken waves. Although the models predict wave-averaged sediment concentrations reasonably well, the corresponding time histories of instantaneous sediment concentration are less accurate. We demonstrate that this is due to the uncertainties in the near-bed sediment boundary conditions. In addition, we show that under breaking waves the near-bed sediment pickup cannot be solely parameterized by the bottom friction, suggesting that other effects may also influence the near-bed sediment boundary conditions.
    Description: This research has been supported by NSF grants CTS-0000675 and OCE-0095834 to Cornell University. This paper is also a resulting product [R/CCP-9] funded under award NA16RG1645 from the National Sea Grant College Program of U.S. Department of Commerce’s National Oceanic and Atmospheric Administration to the Research Foundation of State University of New York on behalf of New York Sea Grant. The financial supports for Tian-Jian Hsu provided by Department of Civil and Environmental Engineering, University of Delaware, and the Coastal Ocean Institute of Woods Hole Oceanographic Institution are also acknowledged.
    Keywords: Turbulent suspension ; Suspended sediment ; Pick-up function
    Repository Name: Woods Hole Open Access Server
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  • 5
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    The landward and seaward mechanisms of fine-sediment transport across intertidal flats in the shallow-water region—A numerical investigation (2012)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Continental Shelf Research 60 Suppl. (2013): S85-S98, doi:10.1016/j.csr.2012.02.003.
    Description: This study investigates transport of fine sediment across idealized intertidal flats with emphasis on resolving processes at the tidal edge, which is defined as the very shallow region of the land-water interface. We first utilize a two-dimensional, vertical numerical model solving the non-hydrostatic Reynolds-averaged Navier-Stokes equations with a k-ε turbulence closure. The numerical model adopts the Volume of Fluid method to simulate the wetting and drying region of the intertidal flat. The model is demonstrated to be able to reproduce the classic theory of tidal-flat hydrodynamics of Friedrichs and Aubrey (1996) and to predict the turbidity at the tidal edge that is similar, qualitatively, to prior field observations. The Regional Ocean Modeling System (ROMS) is also utilized to simulate the same idealized tidal flat to evaluate its applicability in this environment. We demonstrate that when a small critical depth (hcrit =2 cm) in the wetting and drying scheme is adopted, ROMS is able to predict the main features of hydrodynamics and sediment-transport processes similar to that predicted by the RANS-VOF model. When driving the models with a symmetric tidal forcing, both models predict landward transport on the lower and upper flat and seaward transport in the subtidal region. When the very shallow region of the tidal edge is well resolved, both models predict an asymmetry of tidal velocity magnitude between the flood and the ebb that may encourage landward sediment transport on the flat. Further model simulation suggests that the predicted landward transport of sediment on the flat is mainly due to the settling-lag effect while the asymmetry of tidal velocity magnitude may add a lesser but non-negligible amount. When the bed erosion is limited by the availability of soft mud, the predicted transport direction becomes landward in both the subtidal region and on the flat. These results suggest that the tidal flow generally encourages landward transport while significant seaward transport may be caused by other mechanisms. Comparisons with field observations show similarities in the net landward transport on the flat and enhanced stresses and suspended-sediment concentrations near the very shallow region of the tidal edge. The field results also indicate significant transport of sediment occurs through the channels, as a function of three-dimensional processes, which are not incorporated in the present idealized modeling.
    Description: This study is supported by U.S. Office of Naval Research (Littoral Science and Optics program manager Dr. Thomas Drake) as part of the Tidal Flat DRI (N00014-09-1-0134; N00014-11-1-0270). SNC received partial support from Taiwan's National Science Council under grant NSC 100-2119-M-002 -028.
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 6
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    Direct numerical simulations of instability and boundary layer turbulence under a solitary wave (2013)
    Cambridge University Press
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    Publication Date: 2022-05-25
    Description: Author Posting. © Cambridge University Press, 2013. This article is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Journal of Fluid Mechanics 731 (2013): 545-578, doi:10.1017/jfm.2013.361 .
    Description: A significant amount of research effort has been made to understand the boundary layer instability and the generation and evolution of turbulence subject to periodic/oscillatory flows. However, little is known about bottom boundary layers driven by highly transient and intermittent free-stream flow forcing, such as solitary wave motion. To better understand the nature of the instability mechanisms and turbulent flow characteristics subject to solitary wave motion, a large number of direct numerical simulations are conducted. Different amplitudes of random initial fluctuating velocity field are imposed. Two different instability mechanisms are observed within the range of Reynolds number studied. The first is a short-lived, nonlinear, long-wave instability which is observed during the acceleration phase, and the second is a broadband instability that occurs during the deceleration phase. Transition from a laminar to turbulent state is observed to follow two different breakdown pathways: the first follows the sequence of $K$-type secondary instability of a near-wall boundary layer at comparatively lower Reynolds number and the second one follows a breakdown path similar to that of free shear layers. Overall characteristics of the flow are categorized into four regimes as: (i) laminar; (ii) disturbed laminar; (iii) transitional; and (iv) turbulent. Our categorization into four regimes is consistent with earlier works. However, this study is able to provide more specific definitions through the instability characteristics and the turbulence breakdown process.
    Description: This study is supported by National Science Foundation (CMMI-1135026; OCE- 1130217; OCE-1131016).
    Description: 2014-08-28
    Keywords: Coastal engineering ; Solitary waves ; Turbulent flows
    Repository Name: Woods Hole Open Access Server
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  • 7
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    High-resolution numerical modeling of wave-supported gravity-driven mudflows (2010)
    American Geophysical Union
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 114 (2009): C05014, doi:10.1029/2008JC005006.
    Description: Wave-supported gravity-driven mudflow has been identified as a major offshore fine sediment transport mechanism of terrestrial sediment into the coastal ocean. This transport process essentially occurs within the wave boundary layer. In this study, wave-supported gravity-driven mudflow is investigated via a wave-phase-resolving high-resolution numerical model for fluid mud transport. The model results are verified with field observation of sediment concentration and near-bed flow velocities at Po prodelta. The characteristics of wave-supported gravity-driven mudflows are diagnosed by varying the bed erodibility, floc properties (fractal dimension), and rheological stresses in the numerical simulations. Model results for moderate concentration suggest that using an appropriately specified fractal dimension, the dynamics of wave-supported gravity-driven mudflow can be predicted without explicitly incorporating rheological stress. However, incorporating rheological stress makes the results less sensitive to prescribed fractal dimension. For high-concentration conditions, it is necessary to incorporate rheological stress in order to match observed intensity of downslope gravity-driven current. Model results are further analyzed to evaluate and calibrate simple parameterizations. Analysis suggests that when neglecting rheological stress, the drag coefficient decreases with increasing wave intensity and seems to follow a power law. However, when rheological stress is incorporated, the resulting drag coefficient is more or less constant (around 0.0013) for different wave intensities. Model results further suggest the bulk Richardson number has a magnitude smaller than 0.25 and is essentially determined by the amount of available soft mud (i.e., the erodibility), suggesting a supply limited condition for unconsolidated mud.
    Description: This study is supported by the Office of Naval Research grant N00014-09-1-0134 and grant N00014-06-1-0945 as part of the Community Sediment Transport Modeling System (CSTMS) through the National Oceanographic Partnership Program (NOPP). This study is also partially supported by National Science Foundation (OCE- 0644497).
    Keywords: Fluid mud ; Gravity flow ; Wave boundary layer
    Repository Name: Woods Hole Open Access Server
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  • 8
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    A numerical study of sheet flow under monochromatic nonbreaking waves using a free surface resolving Eulerian two‐phase flow model (2018)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 123 (2018): 4693-4719, doi:10.1029/2018JC013930.
    Description: We present a new methodology that is able to concurrently resolve free surface wavefield, bottom boundary layer, and sediment transport processes throughout the entire water column. The new model, called SedWaveFoam, is developed by integrating an Eulerian two‐phase model for sediment transport, SedFoam, and a surface wave solver, InterFoam/waves2Foam, in the OpenFOAM framework. SedWaveFoam is validated with a large wave flume data for sheet flow driven by monochromatic nonbreaking waves. To isolate the effect of free surface, SedWaveFoam results are contrasted with one‐dimensional‐vertical SedFoam results, where the latter represents the oscillating water tunnel condition. Results demonstrate that wave‐averaged total sediment fluxes in both models are onshore‐directed; however, this onshore transport is significantly enhanced under surface waves. Onshore‐directed near‐bed sediment flux is driven by a small mean current mainly associated with velocity skewness. More importantly, progressive wave streaming drives onshore transport mostly in suspended load region due to an intrawave sediment flux. Further analysis suggests that the enhanced onshore transport in suspended load is due to a “wave‐stirring” mechanism, which signifies a nonlinear interaction between waves, streaming currents, and sediment suspension. We present some preliminary efforts to parameterize the wave‐stirring mechanism in intrawave sediment transport formulations.
    Description: Office of Naval Research Grant Number: N00014‐16‐1‐2853; NSF Grant Numbers: OCE‐1635151, OCE‐1356855
    Description: 2019-01-05
    Keywords: Sediment transport ; Multiphase flow ; Surface waves ; Boundary layer streaming ; Sheet flow
    Repository Name: Woods Hole Open Access Server
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  • 9
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    Modeling the morphodynamics of coastal responses to extreme events: what shape are we in? (2022)
    Annual Reviews
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    Publication Date: 2022-10-27
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Sherwood, C. R., van Dongeren, A., Doyle, J., Hegermiller, C. A., Hsu, T.-J., Kalra, T. S., Olabarrieta, M., Penko, A. M., Rafati, Y., Roelvink, D., van der Lugt, M., Veeramony, J., & Warner, J. C. Modeling the morphodynamics of coastal responses to extreme events: what shape are we in? Annual Review of Marine Science, 14, (2022): 457–492, https://doi.org/10.1146/annurev-marine-032221-090215.
    Description: This review focuses on recent advances in process-based numerical models of the impact of extreme storms on sandy coasts. Driven by larger-scale models of meteorology and hydrodynamics, these models simulate morphodynamics across the Sallenger storm-impact scale, including swash,collision, overwash, and inundation. Models are becoming both wider (as more processes are added) and deeper (as detailed physics replaces earlier parameterizations). Algorithms for wave-induced flows and sediment transport under shoaling waves are among the recent developments. Community and open-source models have become the norm. Observations of initial conditions (topography, land cover, and sediment characteristics) have become more detailed, and improvements in tropical cyclone and wave models provide forcing (winds, waves, surge, and upland flow) that is better resolved and more accurate, yielding commensurate improvements in model skill. We foresee that future storm-impact models will increasingly resolve individual waves, apply data assimilation, and be used in ensemble modeling modes to predict uncertainties.
    Description: All authors except D.R. were partially supported by the IFMSIP project, funded by US Office of Naval Research grant PE 0601153N under contracts N00014-17-1-2459 (Deltares), N00014-18-1-2785 (University of Delaware), N0001419WX00733 (US Naval Research Laboratory, Monterey), N0001418WX01447 (US Naval Research Laboratory, Stennis Space Center), and N0001418IP00016 (US Geological Survey). C.R.S., C.A.H., T.S.K., and J.C.W. were supported by the US Geological Survey Coastal/Marine Hazards and Resources Program. A.v.D. and M.v.d.L. were supported by the Deltares Strategic Research project Quantifying Flood Hazards and Impacts. M.O. acknowledges support from National Science Foundation project OCE-1554892.
    Keywords: Coastal morphodynamics ; Extreme storms ; Coastal modeling ; Sandy coasts ; Waves ; Sediment transport
    Repository Name: Woods Hole Open Access Server
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  • 10
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    A numerical study of onshore ripple migration using a Eulerian two-phase model (2021)
    American Geophysical Union
    Details
    Publication Date: 2022-10-20
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(2), (2021): e2020JC016773, https://doi.org/10.1029/2020JC016773.
    Description: A new modeling methodology for ripple dynamics driven by oscillatory flows using a Eulerian two‐phase flow approach is presented in order to bridge the research gap between near‐bed sediment transport via ripple migration and suspended load transport dictated by ripple induced vortices. Reynolds‐averaged Eulerian two‐phase equations for fluid phase and sediment phase are solved in a two‐dimensional vertical domain with a k‐ε closure for flow turbulence and particle stresses closures for short‐lived collision and enduring contact. The model can resolve full profiles of sediment transport without making conventional near‐bed load and suspended load assumptions. The model is validated with an oscillating tunnel experiment of orbital ripple driven by a Stokes second‐order (onshore velocity skewed) oscillatory flow with a good agreement in the flow velocity and sediment concentration. Although the suspended sediment concentration far from the ripple in the dilute region was underpredicted by the present model, the model predicts an onshore ripple migration rate that is in very good agreement with the measured value. Another orbital ripple case driven by symmetric sinusoidal oscillatory flow is also conducted to contrast the effect of velocity skewness. The model is able to capture a net offshore‐directed suspended load transport flux due to the asymmetric primary vortex consistent with laboratory observation. More importantly, the model can resolve the asymmetry of onshore‐directed near‐bed sediment flux associated with more intense boundary layer flow speed‐up during onshore flow cycle and sediment avalanching near the lee ripple flank which force the onshore ripple migration.
    Description: This study is supported by National Science Foundation (Grant no. OCE‐1635151) and Strategic Environmental Research and Development Program (Grant no. MR20‐1478).
    Description: 2021-06-29
    Keywords: Orbital ripples ; Ripple migration ; Sediment transport ; Two‐phase model
    Repository Name: Woods Hole Open Access Server
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