Steady streaming and sediment transport at the bottom of sea waves

2012 ◽  
Vol 697 ◽  
pp. 115-149 ◽  
Author(s):  
Paolo Blondeaux ◽  
Giovanna Vittori ◽  
Antonello Bruschi ◽  
Francesco Lalli ◽  
Valeria Pesarino
Keyword(s):  
Boundary Layer ◽  
Sediment Transport ◽  
Empirical Relationship ◽  
Sediment Concentration ◽  
Sediment Flux ◽  
Transport Rate ◽  
Sea Waves ◽  
Steady Streaming ◽  
Sediment Transport Rate ◽  
Advection Diffusion Equation

AbstractThe flow and sediment transport in the boundary layer at the sea bottom due to the passage of surface waves are determined by considering small values of the wave steepness and of the ratio between the thickness of the boundary layer and the local water depth. Both the velocity field and the sediment transport rate are determined up to the second order of approximation thus evaluating both the steady streaming and the net (wave-averaged) flux of sediment induced by nonlinear effects. The flow regime is assumed to be turbulent and a two-equation turbulence model is used to close the problem. The bed load is evaluated by means of an empirical relationship as function of the bed shear stress. The suspended load is determined by computing the sediment flux, once the sediment concentration is determined by solving an appropriate advection–diffusion equation. The decay of the wave amplitude, which is due to the energy dissipation taking place in the boundary layer, is taken into account. The steady streaming and the sediment transport rate at the bottom of sea waves turn out to be different from those which are observed in a wave tunnel (U-tube), because of the dependence on the streamwise coordinate of the former flow. In particular, in the range of the parameters presently investigated, the sediment transport rate at the bottom of sea waves is found to be always onshore directed while, in a water tunnel (U-tube), the sediment transport rate can be onshore or offshore directed.

scholarly journals SEDIMENT TRANSPORT AT THE BOTTOM OF SEA WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 47
Author(s):  
Giovanna Vittori ◽  
Paolo Blondeaux
Keyword(s):  
Boundary Layer ◽  
Sediment Transport ◽  
Empirical Relationship ◽  
Temporal Distribution ◽  
Sediment Concentration ◽  
Sediment Flux ◽  
Sea Waves ◽  
Wall Boundary Layer ◽  
Sea Bottom ◽  
Local Water

The flow in the wall boundary layer generated close to the sea bottom by the propagation of a monochromatic surface wave is determined by considering small values of both the wave steepness and the ratio between the thickness of the boundary layer and the local water depth. Depending on the hydrodynamic conditions, the sea bottom can be plane or rippled. The geometrical characteristics of the bottom forms are predicted using empirical formulae and, then, the bedforms are assumed to behave as a bottom roughness, the size of which is related to the size of the ripples. The bottom boundary layer is assumed to be turbulent and the flow field is computed by means of a two-equation turbulence model. Then the sediment transport is evaluated. The bed load is obtained using an empirical relationship. The suspended load is determined by computing the sediment flux, once the spatial and temporal distribution of sediment concentration is determined. A comparison of the model findings with the experimental results supports the approach.

scholarly journals TEST OF EMPIRICAL SEDIMENT TRANSPORT RELATIONS AGAINST EXPERIMENTAL SWASH DATA UNDER THE NON-CAPACITY MODELING FRAMEWORK

2018 ◽  
pp. 81
Author(s):  
Peng Hu ◽  
Liming Tan ◽  
Jiafeng Xie ◽  
Zhiguo He
Keyword(s):  
Sediment Transport ◽  
Sediment Concentration ◽  
Transport Rate ◽  
Swash Zone ◽  
Transport Capacity ◽  
Modeling Framework ◽  
Sediment Transport Capacity ◽  
Sediment Transport Rate ◽  
Advection Diffusion Equation ◽  
Empirical Relations

Swash sediment transport and beach deformation has received great attention in the past two decades. Quantification of swash-induced sediment transport rate is of vital importance for accurate prediction of beach deformation in the swash zone. Two empirical parameters are involved in this quantification, empirical relations for sediment transport capacity and the bed shear stress that may be used in the former. Since the swash zone is highly unsteady, of short cross-shore distance, sediment transport in this zone may be of high possibility to be lag of the flow variation. Thus we have firstly developed a non-capacity sediment transport model for the swash zone. This model appreciates the fact that the actual sediment transport rate may not be necessarily equal to the sediment transport capacity of the flow. In contrast to traditional capacity models that calculate sediment transport rate using directly empirical relations (Hu et al. 2015), the non-capacity model uses the advection-diffusion equation to calculate depth-averaged sediment concentration firstly, and afterwards compute sediment transport rate as flow depth*velocity*concentration. We have also noted that some empirical relations for sediment transport capacity may predict physically unrealistic high values of sediment concentration in the swash zone. This is attributed to the vanishing water depth in the swash zone, whereas existing empirical relations are developed for relatively large water depths (Hu et al. 2015; Li et al. 2017).

scholarly journals Suspened sediment concentration and sediment transport rate under asymmetric waves.

1990 ◽  
pp. 295-296
Author(s):  
Shunsuke IKEDA ◽  
Makoto IFUKU ◽  
Tadao KAKINUMA ◽  
Hiromitsu GOTOH
Keyword(s):  
Sediment Transport ◽  
Sediment Concentration ◽  
Transport Rate ◽  
Sediment Transport Rate

scholarly journals SEDIMENT TRANSPORT UNDER SHEET FLOW CONDITION

1982 ◽  
Vol 1 (18) ◽  
pp. 82 ◽  
Author(s):  
Kiyoshi Horikawa ◽  
Akira Watanabe ◽  
Sadakazu Katori
Keyword(s):  
Sediment Transport ◽  
Flow Condition ◽  
Average Rate ◽  
Empirical Relationship ◽  
Sediment Concentration ◽  
Transport Rate ◽  
Sheet Flow ◽  
Load Transport ◽  
Bed Load Transport ◽  
Moving Layer

A series of laboratory experiments in an oscillatory tank was carried out to investigate the sheet flow of sediment. Objectives of the study were to determine the criterion for inception of sheet flow, and to evaluate the sediment transport rate under the sheet flow condition. In order to proceed with the investigation, it was necessary to develop devices appropriate for tracing the sediment particle movement, and for measuring the extremely dense sediment concentration in the moving layer of sheet flow. The chief results are: 1) the criteria for the inception of sheet flow given by Manohar C1955) and by Komar and Miller (1974) are both applicable to materials composed of spheroidal particles, and 2) the average rate of sediment transport for sheet flow is well described by an empirical relationship given by Madsen and Grant (1976) for the bed load transport rate on a plane bed in oscillatory flow.

scholarly journals A Numerical Study of Sheet Flow Driven by Skewed-Asymmetric Shoaling Waves Using SedWaveFoam

2021 ◽  
Vol 9 (9) ◽  
pp. 936
Author(s):  
Yeulwoo Kim ◽  
Ryan S. Mieras ◽  
Dylan Anderson ◽  
Timu Gallien
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Sediment Transport ◽  
Transport Rate ◽  
Phase Lag ◽  
Bed Shear Stress ◽  
Sheet Flow ◽  
Sediment Transport Rate ◽  
Wave Conditions ◽  
The Impact

SedWaveFoam, an OpenFOAM-based two-phase model that concurrently resolves the free surface wave field, and the bottom boundary layer is used to investigate sediment transport throughout the entire water column. The numerical model was validated with large-scale wave flume data for sheet flow driven by shoaling skewed-asymmetric waves with two different grain sizes. Newly obtained model results were combined with previous nonbreaking and near-breaking wave cases to develop parameterization methods for time-dependent bed shear stress and sediment transport rate under various sediment sizes and wave conditions. Gonzalez-Rodriguez and Madsen (GRM07) and quasi-steady approaches were compared for intra-wave bed shear stress. The results show that in strongly asymmetric flows, considering the separated boundary layer development processes at each half wave-cycle (i.e., GRM07) is essential to accurately estimating bed shear stress and highlights the impact of phase-lag effects on sediment transport rates. The quasi-steady approach underpredicts (∼60%) sediment transport rates, especially for fine grains under large velocity asymmetry. A modified phase-lag parameter, incorporating velocity asymmetry, sediment stirring, and settling processes is proposed to extend the Meyer-Peter and Mueller type power law formula. The extended formula accurately estimated the enhanced net onshore sediment transport rate observed under skewed-asymmetric wave conditions.

scholarly journals Suspened sediment concentration and sediment transport rate under asymmetric waves.

1990 ◽  
pp. 293-294
Author(s):  
Hitoshi TANAKA ◽  
Makoto IFUKU ◽  
Tadao KAKINUMA ◽  
Hiromitsu GOTOH
Keyword(s):  
Sediment Transport ◽  
Sediment Concentration ◽  
Transport Rate ◽  
Sediment Transport Rate

scholarly journals Morphodynamic model of the lower Yellow River: flux or entrainment form for sediment mass conservation?

2018 ◽  
Vol 6 (4) ◽  
pp. 989-1010 ◽  
Author(s):  
Chenge An ◽  
Andrew J. Moodie ◽  
Hongbo Ma ◽  
Xudong Fu ◽  
Yuanfeng Zhang ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Yellow River ◽  
Mass Conservation ◽  
Transport Rate ◽  
Entrainment Rate ◽  
Lower Yellow River ◽  
The Lower Yellow River ◽  
Fine Grained ◽  
Sediment Transport Rate ◽  
Sediment Mass

Abstract. Sediment mass conservation is a key factor that constrains river morphodynamic processes. In most models of river morphodynamics, sediment mass conservation is described by the Exner equation, which may take various forms depending on the problem in question. One of the most widely used forms of the Exner equation is the flux-based formulation, in which the conservation of bed material is related to the stream-wise gradient of the sediment transport rate. An alternative form of the Exner equation, however, is the entrainment-based formulation, in which the conservation of bed material is related to the difference between the entrainment rate of bed sediment into suspension and the deposition rate of suspended sediment onto the bed. Here we represent the flux form in terms of the local capacity sediment transport rate and the entrainment form in terms of the local capacity entrainment rate. In the flux form, sediment transport is a function of local hydraulic conditions. However, the entrainment form does not require this constraint: only the rate of entrainment into suspension is in local equilibrium with hydraulic conditions, and the sediment transport rate itself may lag in space and time behind the changing flow conditions. In modeling the fine-grained lower Yellow River, it is usual to treat sediment conservation in terms of an entrainment (nonequilibrium) form rather than a flux (equilibrium) form, in consideration of the condition that fine-grained sediment may be entrained at one place but deposited only at some distant location downstream. However, the differences in prediction between the two formulations have not been comprehensively studied to date. Here we study this problem by comparing the results predicted by both the flux form and the entrainment form of the Exner equation under conditions simplified from the lower Yellow River (i.e., a significant reduction of sediment supply after the closure of the Xiaolangdi Dam). We use a one-dimensional morphodynamic model and sediment transport equations specifically adapted for the lower Yellow River. We find that in a treatment of a 200 km reach using a single characteristic bed sediment size, there is little difference between the two forms since the corresponding adaptation length is relatively small. However, a consideration of sediment mixtures shows that the two forms give very different patterns of grain sorting: clear kinematic waves occur in the flux form but are diffused out in the entrainment form. Both numerical simulation and mathematical analysis show that the morphodynamic processes predicted by the entrainment form are sensitive to sediment fall velocity. We suggest that the entrainment form of the Exner equation might be required when the sorting process of fine-grained sediment is studied, especially when considering relatively short timescales.

Sign in / Sign up

Export Citation Format

Share Document