BOUNDARY LAYER AND SEDIMENT DYNAMICS UNDER SEA WAVES

1999 ◽  
pp. 133-190 ◽  
Author(s):  
P. BLONDEAUX ◽  
G. VITTORI
Keyword(s):  
Boundary Layer ◽  
Sediment Dynamics ◽  
Sea Waves

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 Developments in acoustics for studying wave-driven boundary layer flow and sediment dynamics over rippled sand-beds

2018 ◽  
Vol 166 ◽  
pp. 119-137 ◽  
Author(s):  
Peter D. Thorne ◽  
David Hurther ◽  
Richard D. Cooke ◽  
Ivan Caceres ◽  
Pierre A. Barraud ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Sediment Dynamics ◽  
Layer Flow ◽  
Sand Beds

A new approach of implementation of Wave Boundary Layer in OpenIFS

2021 ◽  
Author(s):  
Nefeli Makrygianni ◽  
Shunqi Pan ◽  
Jean Bidlot ◽  
Michaela Bray
Keyword(s):  
Boundary Layer ◽  
Roughness Length ◽  
Sea Waves ◽  
New Approach ◽  
Wave Boundary Layer ◽  
Theoretical Approaches ◽  
Extreme Wind ◽  
Waves Interaction ◽  
Typhoon Waves ◽  
Wave Boundary

<p>Despite of significant improvement in modelling of the atmosphere after years of research, the accuracy of predicting cyclone/typhoon waves still remains highly challenging. Evidence shows that the air-sea-waves interaction over the ocean surface can significantly impact on the coupled atmosphere-ocean systems, through momentum, mass, and energy exchanges. In particular, the momentum exchanges have been found to affect both the structure of the wave boundary layer and the sea state, through the wave dissipation and wave breaking. For many decades, studies suggested different parameterizations of the momentum fluxes, through drag coefficient (C<sub>d</sub>) and the roughness length (z<sub>0</sub>). In recent years, research has been focused on the theoretical approaches of the momentum parameterization within the Wave Boundary Layer (WBL) in order to obtain the best C<sub>d</sub> and z<sub>0</sub> (Hara and Belcher 2002,2004; Moon et al. 2004; Du et al. 2017,2019). In this study, based on the works of Du et al. (2017, 2019), we introduce a new approach of the parameterization of the momentum flux using the roughness length. The potential of the scheme is analysed with extreme wind and wave events and the results are validated against buoy observations.</p>

Turbulent spots in oscillatory boundary layers

2011 ◽  
Vol 685 ◽  
pp. 365-376 ◽  
Author(s):  
Marco Mazzuoli ◽  
Giovanna Vittori ◽  
Paolo Blondeaux
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Transport Processes ◽  
Stream Velocity ◽  
Detailed Knowledge ◽  
Sea Waves ◽  
Present Contribution ◽  
Turbulent Spots ◽  
Oscillatory Boundary Layer

AbstractDetailed knowledge of the dynamics of vortex structures in an oscillatory boundary layer is essential for the correct modelling of transport processes in many engineering problems and, in particular, of the pick-up and transport of sediments at the bottom of sea waves. In the present contribution, the formation of turbulent spots in an oscillatory boundary layer is investigated by means of direct numerical simulations. Two of the laboratory experiments of Carstensen, Sumer and Fredsøe are reproduced and, after a comparison of the numerical results with laboratory measurements, a detailed and quantitative characterization of the turbulent spots is also given on the basis of further simulations. The speeds of the head (${u}_{1H} $) and tail (${u}_{1T} $) of the spots are found to scale with the instantaneous free stream velocity ${U}_{e} $ and to be similar to those observed in steady boundary layers. The ratios ${u}_{1H} / {U}_{e} $ and ${u}_{1T} / {U}_{e} $ seem to increase with the Reynolds number (${R}_{\delta } $) while the streamwise expansion rate of the spots appears to be independent of ${R}_{\delta } $.

scholarly journals STEADY CURRENTS INDUCED BY SEA WAVES PROPAGATING OVER A SLOPING BOTTOM

2011 ◽  
Vol 1 (32) ◽  
pp. 35
Author(s):  
Erminia Capodicasa ◽  
Pietro Scandura ◽  
Foti Enrico
Keyword(s):  
Boundary Layer ◽  
Small Amplitude ◽  
Core Region ◽  
Sea Waves ◽  
Mean Velocity ◽  
Reflected Waves ◽  
First Order ◽  
The Mean ◽  
Sea Wave ◽  
Sloping Bottom

A numerical model aimed at computing the mean velocity generated by a sea wave propagating over a sloping bottom, offshore the breaker line, is presented. The model is based on the assumption that the fluid domain can be partitioned into two boundary layers and a core region where at a first order of approximation the flow can be regarded as irrotational. The irrotational flow is computed by using a theory based on the assumption of small amplitude waves which allows both fully absorbed waves and partially reflected waves at the coastline to be considered. The distribution of the mean velocity is controlled by the ratio between the thickness of the boundary layer and the wave amplitude. When this ratio is small, the mean velocities are rather constant along the depth and a second boundary layer develops close to the bottom. In the case of fully reflected waves such boundary layer separates and the mean vorticity can be convected far from the bottom.

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.

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