Near-bed hydrodynamics and turbulence below a large-scale plunging breaking wave over a mobile barred bed profile

Funded by The research presented in this paper is part of the SINBAD project. Grant Number: STW (12058) and EPSRC (EP/J00507X/1, EP/J005541/1)Peer reviewedPublisher PDFPublisher PD

Coastal sediment dynamics: recent advances and future research needs

This vision paper discusses the advances made over the last three decades in coastal sand transport and morphodynamics, and the research needs for the coming decades. The prime focus of the paper is on the relationship between the transport of sand particles and fluid motions in the coastal environment based on laboratory and field experiments as well as mathematical modelling. The paper mainly focuses on two main issues: (1) better understanding of sediment transport processes in the coastal zone and (2) the development of improved practical engineering sand transport formulae and morphodynamic models

Near-Bed Turbulent Kinetic Energy Budget Under a Large-Scale Plunging Breaking Wave Over a Fixed Bar

Hydrodynamics under regular plunging breaking waves over a fixed breaker bar were studied in a large-scale wave flume. A previous paper reported on the outer flow hydrodynamics; the present paper focuses on the turbulence dynamics near the bed (up to 0.10 m from the bed). Velocities were measured with high spatial and temporal resolution using a two component laser Doppler anemometer. The results show that even at close distance from the bed (1 mm), the turbulent kinetic energy (TKE) increases by a factor five between the shoaling, and breaking regions because of invasion of wave breaking turbulence. The sign and phase behavior of the time-dependent Reynolds shear stresses at elevations up to approximately 0.02 m from the bed (roughly twice the elevation of the boundary layer overshoot) are mainly controlled by local bed-shear-generated turbulence, but at higher elevations Reynolds stresses are controlled by wave breaking turbulence. The measurements are subsequently analyzed to investigate the TKE budget at wave-averaged and intrawave time scales. Horizontal and vertical turbulence advection, production, and dissipation are the major terms. A two-dimensional wave-averaged circulation drives advection of wave breaking turbulence through the near-bed layer, resulting in a net downward influx in the bar trough region, followed by seaward advection along the bar's shoreward slope, and an upward outflux above the bar crest. The strongly nonuniform flow across the bar combined with the presence of anisotropic turbulence enhances turbulent production rates near the bed

Practical sand transport formula for non-breaking waves and currents

Open Access funded by Engineering and Physical Sciences Research Council Under a Creative Commons license Acknowledgements This work is part of the SANTOSS project (‘SANd Transport in OScillatory flows in the Sheet-flow regime’) funded by the UK's EPSRC (GR/T28089/01) and STW in The Netherlands (TCB.6586). JW acknowledges Deltares strategic research funding under project number 1202359.09. Richard Soulsby is gratefully acknowledged for valuable discussions and feedback on the formula during the SANTOSS project.Peer reviewedPostprin

Sediment transport in non-linear skewed oscillatory flows : the TRANSKEW experiments

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Sediment transport distribution along equilibrium sand dunes

Abstract The present study focuses on distribution of sediment transport along mobile dunes in equilibrium. To this end, using ACVP (Acoustic Concentration and Velocity Profiler), we have obtained simultaneous, co-located, high temporal-spatial resolution measurements of the multi-component flow velocity and suspended sediment concentration above dunes. In contrast to previous measurements of flow and sediment dynamics above dunes which are mostly carried out with more than one instrument, we are now able to address sediment fluxes directly for flow scales smaller than the separation distance between different instruments. In this paper, preliminary ACVP results are shown in terms of flow velocities, suspended sediment concentrations and suspended sediment fluxes along dune profiles