Sediment Transport Under Energetic Waves: From Ripples to Sheet Flow

Primary Investigators: T.-J. Hsu (UD), P. Traykovski (WHOI), Z. Cheng (WHOI)

Collaborators: J. Chauchat (LEGI), D. Hurther (LEGI).

Project Summary:

Bedform migration and sheet flows are the major modes of sediment transport between the inner-shelf and the surf zone. The geometry of these bedforms also determines hydrodynamic dissipation. We propose a tightly integrated research effort of analysis of previously collected field data and numerical simulation to understand evolution and transport from bedforms to sheet flows.  A novel turbulence-resolving (or turbulence-averaged) Eulerian two-phase sediment transport model without a priori assumption of bedload and suspended load will be validated and used to simulate field observed events to provide high resolution 3D/2D fields. Findings will then be used to inform the creation of new parameterizations that can be adopted by coastal evolution models.

The primary goal of this study is to investigate the dominant mechanisms driving the migration and evolution of bedfroms and the transition to sheet flows. A newly developed two-phase model SedFoam will be used to carry out simulations guided by comprehensive analysis of field observational data. The proposed effort to understand mechanisms driving migration and evolution of bedforms can improve the concept of depth of closure, which is key to the prediction shoreline response subject to accelerated sea-level rise. Improved quantitative prediction on bedform geometry is essential information for ocean exploration and large-scale hydrodynamic prediction. The numerical model, SedFoam, adopted in this study has already been disseminated as open-source model through Community Surface Dynamics and Systems (CSDMS) model repository. The proposed work will significantly enhance this open-source model with turbulence-resolving capability for ripple simulation and this new model will also be disseminated as open-source.

Products:

Salimi Tarazonj, A., Hsu, T.-J., Traykovski, P., Cheng, Z., Chauchat, J. (2020) A numerical study of onshore ripple migration using a Eulerian two-phase model, J. Geophys. Res. Oceans, in press.  

Open-source model is available at http://servforge.legi.grenoble-inp.fr/pub/soft-sedfoam/

Kim, Y., Cheng, Z., Hsu, T.-J., & Chauchat, J. (2018). A numerical study of sheet flow under monochromatic nonbreaking waves using a free surface resolving Eulerian two-phase flow model. Journal of Geophysical Research: Oceans, 123, 4693–4719. 

Open source model SedWaveFoam-1.0 available at: https://github.com/sedwavefoam/sedwavefoam ;

Case setup at https://github.com/sedwavefoam/Dohmen-Janssen-and-Hanes-2002

Cheng, Z., Hsu, T.-J., and Chauchat, J. (2018) An Eulerian two-phase model for steady sheet flow using large-eddy simulation methodology, Advances in Water Resources, 111, 205-223.

Chauchat, J., Cheng, Z., Nagel, T., Bonamy, C., and Hsu, T.-J. (2017) SedFoam-2.0: a 3D two-phase flow numerical model for sediment transport, Geosci. Model Dev., 10, 4367-4392.

Open source model SedFoam-2.0 available via CSDMS: https://csdms.colorado.edu/wiki/Model:SedFoam-2.0