scholarly journals SWASH ZONE MORPHODYNAMICS OF COARSE-GRAINED BEACHES DURING ENERGETIC WAVE CONDITIONS

2014 ◽  
Vol 1 (34) ◽  
pp. 35 ◽  
Author(s):  
Luis Pedro Almeida ◽  
Gerd Masselink ◽  
Paul Russell ◽  
Mark Davidson ◽  
Robert McCall ◽  
...  
Keyword(s):  
Coarse Grained ◽  
Swash Zone ◽  
Wave Conditions

scholarly journals SIMULTANEOUS SURFACE AND SUBSURFACE AIR AND WATER FLOWS MODELLING IN THE SWASH ZONE

2012 ◽  
Vol 1 (33) ◽  
pp. 56 ◽  
Author(s):  
Jonathan Desombre ◽  
Denis Morichon ◽  
Mathieu Mory
Keyword(s):  
Numerical Simulation ◽  
Laboratory Data ◽  
Subsurface Flow ◽  
Momentum Equation ◽  
Coarse Grained ◽  
Swash Zone ◽  
Data Set ◽  
Water Flows ◽  
Subsurface Flows ◽  
The University

This study presents the results of the numerical simulation of a bore-driven swash flow over a permeable coarse- grained beach, carried out using the THETIS code. This code, based on a VOF-RANS approach, was previously used to simulate the swash flow over an impermeable beach (Desombre et al. 2013). For the present study, the code is extended to account for infiltration and exfiltration into a permeable immobile beach using the Volume-Averaged momentum equation that solves simultaneously the surface and subsurface flows. The results are compared with a laboratory data set from an experiment performed in the swash facility of the University of Aberdeen (Steenhauer et al. 2011). Comparisons between measurements and model results show the ability of the model to simulate the main features of subsurface flow during an entire swash cycle.

scholarly journals SWASH ZONE BASED REFLECTION DURING ENERGETIC WAVE CONDITIONS AT A DISSIPATIVE BEACH: TOWARD A WAVE-BY-WAVE APPROACH

2014 ◽  
Vol 1 (34) ◽  
pp. 34 ◽  
Author(s):  
Rafael Almar ◽  
Patricio Catalan ◽  
Raimundo Ibaceta ◽  
Christopher Blenkinsopp ◽  
Rodrigo Cienfuegos ◽  
...  
Keyword(s):  
Swash Zone ◽  
Wave Approach ◽  
Wave Conditions

scholarly journals EXPERIMENTAL AND NUMERICAL STUDIES ON WAVE PROPAGATION OVER COARSE GRAINED SLOPING BEACH

2011 ◽  
Vol 1 (32) ◽  
pp. 26 ◽  
Author(s):  
Tai-Wen Hsu ◽  
Jian-Wu Lai ◽  
Yuan-Jyh Lan
Keyword(s):  
Wave Propagation ◽  
Velocity Field ◽  
Porous Layer ◽  
Surf Zone ◽  
Three Dimensional ◽  
Coarse Grained ◽  
Swash Zone ◽  
Sloping Bed ◽  
Sloping Beach ◽  
Three Dimensional Simulations

In this paper, the hydrodynamics and turbulence on wave propagation over coarse grained sloping beach is investigated by both experimental and numerical methods. The coarse grained sloping beach was conducted over a 1:5 smooth inclined bottom with two layers of spherical balls. A set of newly and rarely experimental data for the distribution and evolution of the wave and velocity field over porous sloping beach were measured in this study. The particle image velocimetry (PIV) and digital image process (DIP) techniques are employed to measure the flow field and free surface both inside and outside regions for a coarse grain porous sloping bed. Eleven fields of views (FOVs) were integrated to represent the global results converting the entire propagating waves from the outer to the inner surf zones and swash zones. In addition, a high-resolution CCD Camera was constructed to capture wave propagating images continuously. Subsequent digital image processing (DIP) techniques that including image enhancement, coordinate transformation, edge detection and sub-pixel concept for resolution advancement were developed to analysis the image and get the information of wave motions. In this experimental study, the PIV and DIP techniques offer a possibility for measuring full scale spatio-temporal information of the wave motions and velocity field within / without the porous sloping bed without instructive instrument. Furthermore, the FLOW-3D which based on the Navier-Stokes equations was adopted for CFD computations. The direct three-dimensional simulations were employed for simulating wave profile and velocity field for the sloping beach. Numerical results were favorably compared with experiments to examine the validity of the model. According to the comparison of the wave and velocity data of hydraulic physical model with computational results, the direct three-dimensional simulations method can offer results much agreement with the experimental data in the global regions. The results showed that direct three-dimensional simulations can resolve the wave and velocity profile more complete and reasonable descriptions from outer to the inner porous layer and it is true no matter in the surf zone, swash zone and within the porous layer. Moreover, according to the experimental analysis, the process of the turbulence characteristics of the maximum turbulent kinetic energy, turbulent kinetic energy dissipation rate and turbulence intensity occurred between the toe of breaker and surface of porous layer. In addition, general discussion of hydrodynamics and turbulence on wave propagation over coarse grained sloping beach and impermeable sloping bed were investigated with the results of direct three-dimensional simulations in this study. The results showed that wave propagation over coarse grained sloping beach effects the breaker types in the shallow water, i.e. the steepening and overturning of the front face due to plunging breaker over impermeable sloping beach becomes indistinctively and the breaker type transform into the collapsing type. Besides, the dissipation of wave energy due to the role of infiltration and friction are significant differences from surf zone to swash zone between the coarse grained and impermeable sloping beach.

scholarly journals WAVE RUN-UP OBSERVATION AND 2DV NUMERICAL INVESTIGATION ON BEACHES PROTECTED BY STRUCTURES

2012 ◽  
Vol 1 (33) ◽  
pp. 20
Author(s):  
Renata Archetti ◽  
Maria Gabriella Gaeta
Keyword(s):  
Numerical Models ◽  
Wave Spectrum ◽  
Low Frequency ◽  
Swash Zone ◽  
Flow Motion ◽  
Transmission Area ◽  
Wave Conditions ◽  
Run Up ◽  
Incident Waves

The main parameter for the assessment of coastal vulnerability and sediment transport is the wave run-up on the beach, defining the limit of maximum flooding, but also hydrodynamic properties in the Swash Zone (SZ) are trivial for the comprehension of hydro-morphodynamic processes. Several studies have been carried out on the SZ but few literature is still available on the run-up and on SZ flows on beaches protected by Low Crested Structures (LCSs), where flow motion is driven by a combination of low frequency infra-gravity waves and incident waves. In presence of breakwaters, swash incident waves are transmitted through the structure. In the transmission area behind the structures, wave energy is shifted to higher frequencies with respect to the incident wave spectrum and in general its mean period considerably decreases with respect to the incident one. Collecting in situ run-up measurements during storms is essential to understand the SZ processes and properly calibrate their both empirical and numerical models but measuring extreme run-up is difficult, due to the severe sea conditions and due to unexpected nature of storms. The present paper present a numerical and experimental analysis of the wave run-up and of the flow properties on a beach: the study shows the different behavior of unprotected and protected beach, subjected to the same wave conditions. In particular the paper shows that submerged breakwaters reduce in general the run-up height, on the basis of the calibrated 2DV numerical simulations, under extreme wave conditions (TR >50 years), the effect of submerged breakwaters seems to be negligible on the run-up height. Moreover a preliminary empirical equation for run-up with protected beach is proposed

scholarly journals LARGE SCALE TESTS ON FORESHORE EVOLUTION DURING STORM SEQUENCES AND THE PERFORMANCE OF A NEARLY VERTICAL STRUCTURE

2018 ◽  
pp. 13 ◽  
Author(s):  
Riccardo Briganti ◽  
Rosaria Ester Musumeci ◽  
Jentsje Van der Meer ◽  
Alessandro Romano ◽  
Laura Maria Stancanelli ◽  
...  
Keyword(s):  
Large Scale ◽  
Water Levels ◽  
Beach Sand ◽  
Swash Zone ◽  
The European Union ◽  
Large Wave ◽  
Wave Flume ◽  
Wave Conditions ◽  
Almost All ◽  
Large Scale Tests

This work presents the results of an experimental investigation on the effects of a sequence of storms on wave overtopping at a nearly vertical battered seawall at the back of a sandy foreshore. The experiments were carried out in the Large Wave Flume (GWK) at Leibniz Universität Hannover (Germany), as part of the research project ICODEP (Impact of Changing fOreshore on flood DEfence Performance), within the European Union programme Hydralab+. The layout consisted of a 10/1 battered seawall and a natural sandy foreshore with an initial 1:15 slope. The beach sand had a nominal diameter of 0.30 mm. Three storm sequences were simulated, where each consisted of three individual storms. Each storm was divided into six steps in which the wave conditions and still water level were varied to represent the peak of an actual storm. The six sea states were based on a JONSWAP spectral shape, with wave heights roughly between 0.6 m and 0.8 m. Two still water levels were tested. For the central two steps the level was such that the freeboard was only 0.14 m and almost all waves were overtopping. In the remaining steps low still water levels were employed, leaving a narrow swash zone. Two storm profiles were considered, the first one with a lower level of energy and the second one with a higher one. These were combined in the three different sequences. All the tested wave conditions were designed to be erosive for the beach, with no recovery in between. Each sequence started from a plain beach configuration and the beach was not restored in between storms. The measurements included waves, pressure and forces, sediment concentrations and flow velocity together with overtopping. The profile of the beach was measured after each sea state tested.

scholarly journals Small-Scale Morpho-Sedimentary Dynamics in the Swash Zone of a Megatidal Mixed Sand–Gravel Beach

2021 ◽  
Vol 9 (4) ◽  
pp. 413
Author(s):  
Tristan B. Guest ◽  
Alex E. Hay
Keyword(s):  
Remote Sensing ◽  
Grain Size ◽  
Coarse Grained ◽  
Small Scale ◽  
Swash Zone ◽  
Sediment Grain Size ◽  
Mean Grain Size ◽  
Sedimentary Dynamics ◽  
Gravel Beaches ◽  
Gravel Beach

On mixed sand–gravel beaches, impacts from gravel- and cobble-sized grains—mobilized by the energetic shorebreak—limit the utility of in situ instrumentation for measuring the small-scale response of the beach face on wave period time scales. We present field observations of swash zone morpho-sedimentary dynamics at a steep, megatidal mixed sand–gravel beach using aeroacoustic and optical remote sensing. Coincident observations of bed level and mean surficial sediment grain size in the swash zone were obtained using an array of optical cameras paired with acoustic range sensors. Lagrangian tracking of swash-transported cobbles was carried out using an additional downward-oriented camera. The principal objective of the study was to investigate linkages between sediment grain size dynamics and swash zone morphological change. In general, data from the range sensor and camera array show that increases in bed level corresponded to increases in mean grain size. Finer-scale structures in the bed level and mean grain size signals were observable over timescales of minutes, including signatures of bands of coarse-grained material that migrated shoreward with the leading edge of the swash prior to high tide berm formation. The direction and magnitude of cobble transport in the swash varied with cross-shore position, and with the composition of the underlying bed. These results demonstrate that close-range remote sensing techniques can provide valuable insights into the roles of cobble-sized versus sand-sized particle dynamics in the swash zone on mixed sand–gravel beaches.

scholarly journals Lidar Observations of the Swash Zone of a Low-Tide Terraced Tropical Beach under Variable Wave Conditions: The Nha Trang (Vietnam) COASTVAR Experiment

2020 ◽  
Vol 8 (5) ◽  
pp. 302 ◽  
Author(s):  
Luís Pedro Almeida ◽  
Rafael Almar ◽  
Chris Blenkinsopp ◽  
Nadia Senechal ◽  
Erwin Bergsma ◽  
...  
Keyword(s):  
Field Experiment ◽  
Wave Height ◽  
Sandy Beach ◽  
Wind Waves ◽  
Swash Zone ◽  
Key Factor ◽  
Wave Conditions ◽  
Run Up ◽  
Topographic Surveys ◽  
Lidar Observations

A field experiment was conducted at a tropical microtidal intermediate sandy beach with a low tide terrace (Nha Trang, Vietnam) to investigate the short-term swash-zone hydrodynamics and morphodynamics under variable wave conditions. Continuous 2D Lidar scanner observations of wave height at the lower foreshore, subsequent run-up and swash-induced topographic changes were obtained. These data were complemented by detailed real-time kinematic GPS topographic surveys. Variable wave and tide conditions were experienced during the field experiment with relatively large swell waves (offshore significant wave height, Hs = 0.9 m to 1.3 m; peak wave period, Tp = 8 to 12 s) concomitant with spring tides at the beginning of the period, followed by mild wind waves (offshore Hs under 0.5 m and Tp 5 s) and neap tides. This resulted in the following morphological sequence: berm erosion followed by rapid neap berm reformation and beach recovery within a few days. New insights into the link between intra-tidal swash dynamics and daily beach profile evolution were found using the Lidar dataset. While waves directly cause morphology changes on a wave-by-wave basis, tidal levels were found to be a key factor in determining the morphological wave-effect (accretive or erosive) due to modulated interaction between surf and swash hydro-morphodynamics.

scholarly journals OBSERVATIONS OF SEDIMENT PARTICLE MOVEMENTS UNDER ACCRETIVE WAVE CONDITIONS

2018 ◽  
pp. 68
Author(s):  
Takayuki Suzuki ◽  
Yu Inami ◽  
Shinichi Yanagishima ◽  
Shuhei Sakihama ◽  
Daniel Cox
Keyword(s):  
Surf Zone ◽  
Outer Side ◽  
Field Observations ◽  
Swash Zone ◽  
Sediment Particle ◽  
Beach Management ◽  
Sediment Movement ◽  
Recovery Duration ◽  
Wave Conditions

From the aspect of beach management, understanding of sediment movement from the outer-surf zone to the swash zone during recovery duration is important. In this study, field observations were conducted during accretive wave conditions to investigate the sediment movement from the outer side of the bar to the swash zone using fluorescent sand tracers.

The Alteration of the Pore Spaces in Sandstones

1973 ◽  
Vol 31 ◽  
pp. 210-211
Author(s):  
R. E. Ferrell ◽  
G. G. Paulson
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
The Other ◽  
Coarse Grained ◽  
Depositional Fabric ◽  
Soluble Components ◽  
Scanning Electron ◽  
Shape And Size

The pore spaces in sandstones are the result of the original depositional fabric and the degree of post-depositional alteration that the rock has experienced. The largest pore volumes are present in coarse-grained, well-sorted materials with high sphericity. The chief mechanisms which alter the shape and size of the pores are precipitation of cementing agents and the dissolution of soluble components. Each process may operate alone or in combination with the other, or there may be several generations of cementation and solution.The scanning electron microscope has ‘been used in this study to reveal the morphology of the pore spaces in a variety of moderate porosity, orthoquartzites.

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