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  • 1
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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
    Type: Article
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  • 2
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    Eddy interaction model for turbulent suspension in Reynolds-averaged Euler-Lagrange simulations of steady sheet flow (2018)
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Advances in Water Resources 111 (2018): 435-451, doi:10.1016/j.advwatres.2017.11.019.
    Description: A Reynolds-averaged Euler–Lagrange sediment transport model (CFDEM-EIM) was developed for steady sheet flow, where the inter-granular interactions were resolved and the flow turbulence was modeled with a low Reynolds number corrected turbulence closure modified for two-phase flows. To model the effect of turbulence on the sediment suspension, the interaction between the turbulent eddies and particles was simulated with an eddy interaction model (EIM). The EIM was first calibrated with measurements from dilute suspension experiments. We demonstrated that the eddy-interaction model was able to reproduce the well-known Rouse profile for suspended sediment concentration. The model results were found to be sensitive to the choice of the coefficient, C0, associated with the turbulence-sediment interaction time. A value was suggested to match the measured concentration in the dilute suspension. The calibrated CFDEM-EIM was used to model a steady sheet flow experiment of lightweight coarse particles and yielded reasonable agreements with measured velocity, concentration and turbulence kinetic energy profiles. Further numerical experiments for sheet flow suggested that when C0 was decreased to C0 〈 3, the simulation under-predicted the amount of suspended sediment in the dilute region and the Schmidt number is over-predicted (Sc 〉 1.0). Additional simulations for a range of Shields parameters between 0.3 and 1.2 confirmed that CFDEM-EIM was capable of predicting sediment transport rates similar to empirical formulations. Based on the analysis of sediment transport rate and transport layer thickness, the EIM and the resulting suspended load were shown to be important when the fall parameter is less than 1.25.
    Description: Z. Cheng and T.-J. Hsu were supported by the U.S. Office of Naval Research (N00014- 16-1-2853) and National Science Foundation (OCE- 1537231). J. Chauchat was supported by the Région Rhones-Alpes (COOPERA project and Explora Pro grant) and the French national programme EC2CO-LEFE MODSED. J. Calantoni was supported under base funding to the U.S. Naval Research Laboratory from the U.S. Office of Naval Research. The authors would also like to acknowledge the support from the program on "Fluid- Mediated Particle Transport in Geophysical Flows" at the Kavli Institute for Theoretical Physics, Santa Barbara, USA.
    Keywords: Euler-Lagrange model ; Eddy interaction model ; Turbulent suspension ; Steady sheet flow ; Rouse profile ; Sediment transport rate
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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