Study of Extreme Waves Propagating Over Reefs in Large Wave Flume

2019 ◽  
Author(s):  
Songgui Chen ◽  
Zeming Wang ◽  
Jinhai Zheng ◽  
Chi Zhang ◽  
Ke Hu
Keyword(s):  
Wave Breaking ◽  
Surf Zone ◽  
Structure Design ◽  
Water Levels ◽  
Extreme Waves ◽  
Extreme Wave ◽  
Large Wave ◽  
Wave Flume ◽  
Breaking Points ◽  
Wave Induced

Abstract Waves propagating over reefs have been studied by many researchers. However due to limitation of small wave flume, most experiments focused on the normal waves. Extreme waves are the input parameters for structure design on reefs. Thus, experiments of extreme waves propagating over reefs were conducted in the large wave flume of the Tianjin Research Institute of Water Transport Engineering. Extreme wave hydrodynamic within surf zone will be focused on. Tests with different wave heights Hi, wave periods T and water levels on reefs h have been carried out. The model scale is set to be 1:15, then Hi from 4.5m to 12m, T from 9s to 17s, hr from 0 to 3m are generated in the test. Wave breaking points are observed by high speed camera. Wave breaking points move offshore as Hi and T increase and h decrease. Wave setups and wave-induced flows along the reef are measured at different locations. It can be found that wave setups increase with increasing Hi and T and decreasing water level h. Wave-induced flows increase with increasing Hi and h and decreasing T. As waves propagate towards landside, wave setups and wave-induced flows have a local extremum at the middle of surf zone. Compared with our test, Gourlay’s formulas overestimate wave setup while underestimate wave induced flow within extreme wave surf zone.

scholarly journals SHOREWARD SAND TRANSPORT OUTSIDE THE SURFZONE, NORTHERN GOLD COAST, AUSTRALIA

2012 ◽  
Vol 1 (33) ◽  
pp. 26 ◽  
Author(s):  
Dean Patterson
Keyword(s):  
Surf Zone ◽  
River Mouth ◽  
Transport Processes ◽  
Gold Coast ◽  
Sand Transport ◽  
Large Wave ◽  
Wave Flume ◽  
Shoreline Evolution ◽  
The One

To date, no suitable theoretical basis has been derived to predict with reliable accuracy the shoreward sand transport under waves in the deeper water outside the surf zone. This is important for understanding the rate of recovery of beaches after major storm erosion and, in some circumstances, to quantify net shoreward supply of sand to the shoreline from the active lower shore-face below the depth of storm erosion bar development. Even a relatively low rate of long term shoreward net supply may contribute to shoreline stability where it offsets a gradient in the longshore sand transport that would otherwise lead to recession. This paper outlines the results of analysis of a 41 year dataset of beach and nearshore profile surveys to quantify annual average rates of shoreward net sand transport in 6-20m water in an area where the profiles are not in equilibrium due to the existence of a residual river mouth ebb delta bar lobe. Additionally, an empirical adaptation of the sheet flow relationship of Ribberink and Al-Salem (1990) to provide for the effects of ripples has been derived from large wave flume data and correlates well with the measured Gold Coast transport rates. These have been applied to a new coastline modelling system developed as part of research into the long term evolution of Australia’s central east coast region in response to sea level change and longshore sand transport processes, which combines the one-line concept of shoreline profile translation within the zone of littoral sand transport with cross-shore profile evolution across the deeper shore-face profile below that zone. It demonstrates the importance of providing for both the shoreward supply from the continental shelf and the varying profile response time-scale across the shore-face in predicting shoreline evolution.

Observations of wave attenuation, scour, and subsurface pore pressures acrossbthree marsh restoration sill structures on a sandy bed

Shore & Beach ◽  
2020 ◽  
pp. 14-30
Author(s):  
Jordan Converse ◽  
Meagan Wengrove ◽  
Pedro Lomonaco
Keyword(s):  
Sediment Transport ◽  
Large Scale ◽  
Wave Attenuation ◽  
Oyster Shell ◽  
Water Levels ◽  
Structure Stability ◽  
Large Wave ◽  
Sea Levels ◽  
Wave Flume ◽  
Living Shoreline

With rising sea levels and more frequent exposure to extreme storms, coastlines worldwide are vulnerable to increased erosion and loss of natural marsh lands. In an effort to lessen these impacts, there is a growing practice of adapting hard or “gray” coastline protection techniques to more nature-based features that promote habitat and ecosystem health. Living shoreline marsh restorations utilize natural and naturebased materials to protect marsh shores from erosion while also allowing intertidal flushing to promote the health and diversity of the marsh. Our study investigates three types of living shoreline sill designs exposed to average and storm-energy wave conditions at varying water levels. The sills were designed to mimic constructed sills in practice (rock, oyster shell, tree root wads), but more generally vary in structure porosity and material dissipation potential. Large-scale laboratory experiments were conducted in the large wave flume at the O.H. Hinsdale Wave Research Laboratory. Wave transmission and reflection are used to demonstrate wave attenuation capability of each sill structure. Scour of the sill, bedload sediment transport rates on the seaward and shoreward sides of the sill, and sediment pore-water vertical hydraulic gradients were used to demonstrate the potential for sediment transport and liquefaction. Results will contribute to understanding the effect of sill material porosity and mass on structure stability, and the effectiveness of using green living shoreline sill structures in the continued effort to establish design criteria for living shoreline implementation.

scholarly journals MEASUREMENTS OF THE STEADY CURRENTS OUTSIDE THE SURF ZONE

2011 ◽  
Vol 1 (32) ◽  
pp. 49 ◽  
Author(s):  
Pietro Scandura ◽  
Erminia Capodicasa ◽  
Enrico Foti
Keyword(s):  
Surf Zone ◽  
Scale Effects ◽  
Velocity Profiles ◽  
Sea Waves ◽  
Mean Velocity ◽  
Large Wave ◽  
Wave Flume ◽  
Wave Trough ◽  
Steady Current ◽  
The Mean

The results of an experimental study concerning with the measurements of the steady current induced by sea waves approaching the coast are reported. The experiments have been performed in a large wave flume in order to minimize the scale effects. The measurements have been carried out at four different stations along the wave flume by using Acoustic Doppler Velocimeters. The results show that the mean velocity profiles are significantly influenced by the wave period. In particular, when the period reduces the mean velocity gradient close to the wave trough increases. The trend of the velocity profiles is different from that predicted by the theory and mostly reported by other experiments. However, experimental results are reported in literature which are in a qualitative agreement with the present ones.

An Experimental Study of Wave-Induced Set-Up Over a Horizontal Reef With an Idealized Ridge

2009 ◽  
Author(s):  
Yu Yao ◽  
Edmond Y. M. Lo ◽  
Zhenhua Huang ◽  
Stephen G. Monismith
Keyword(s):  
Water Level ◽  
Wave Breaking ◽  
Transformation Process ◽  
Wave Transformation ◽  
Reflected Waves ◽  
Wave Flume ◽  
Breaking Mechanism ◽  
Set Up ◽  
Wave Induced ◽  
Reef Edge

Wave action has been the primary focus of near-shore hydrodynamic studies over decades. The wave-induced set-up due to wave breaking is one of the important factors to consider in determining both water level and mass transport above the reef-top, which has ecological as well as engineering significance. Previous investigations into reef hydrodynamics (including laboratory experiments, field investigations, theoretical analysis and numerical simulations) focused mainly on wave-induced set-up on reefs with a horizontal reef-top (Gourlay, 1996. J. Coastal Eng. 27:161–193). It has been observed that a ridge (reef crest) may be present at the reef edge, but so far we are not aware of any published studies on the effects of this type of ridge on the wave-induced set-up over the reef-top. To understand the role of the ridge in wave-breaking mechanism and wave-induced set-up over the reef, a series of experiments were carried out in a wave flume of 36m long and 0.55m wide, with idealized reef-ridge models being installed at the reef edge to simulate fringing reefs with rectangle ridges. The surface elevations at four locations over the reef were measured with Ultralab sensors (General Acoustics), revealing the variation of wave-induced set-up along the reef. Experimental results are reported for two water depths and eighteen regular wave conditions. Also discussed are the effects of the ridge width on the wave-induced set-up. The focus of this paper will be given to the comparison of wave-induced set-ups with and without the rectangular ridges. Preliminary analysis shows that the ridge controls the water level above the reef-top in a way similar to that a broad crest weir controls the water level in open channel flows. Furthermore, the presence of the ridge is found to alter significantly the wave transformation process near the reef edge, especially the strength of the reflected waves and the locations of breakers. Experiments also show that the wave-induced set-up over reef-top with a ridge is generally much larger than that without a ridge. Finally, an attempt is made to introduce a new dimensionless parameter in order to take the ridge configuration into consideration and achieve a better agreement between experiments and predictions when ridges are present.

scholarly journals 2D OVERTOPPING AND IMPACT EXPERIMENTS IN SHALLOW FORESHORE CONDITIONS

2018 ◽  
pp. 67
Author(s):  
Vincent Gruwez ◽  
Ine Vandebeek ◽  
Dogan Kisacik ◽  
Maximilian Streicher ◽  
Corrado Altomare ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Surf Zone ◽  
High Spatial Resolution ◽  
Wave Structure ◽  
High Energy ◽  
Water Levels ◽  
Wave Transformation ◽  
Wave Overtopping ◽  
Typical Situation ◽  
Wave Flume

This paper introduces the 2D experiments conducted for the CREST project in the wave flume of Ghent University. The experiments focus on wave interactions with low-crested sea dikes fronted by a shallow foreshore and mildly to steeply sloping beaches, which is a very typical situation along the Belgian coast. Foreshore slopes of 1/20, 1/35, 1/50 and 1/80 were tested for a range of low to high energy wave conditions, a variation in wave steepness and two water levels. The main goal was to obtain a dataset in which the effects of the infragravity waves on the wave-structure interactions (i.e. wave overtopping and impact forces) can be studied. The tests included high spatial resolution surface elevation measurement tests, which is new for beaches including a dike in the inner surf zone. From the first results it became clear that the foreshore slope influences the wave transformation up to the dike toe. The influence is apparent comparing to existing (semi-) empirical models for prediction of the spectral wave period at the dike toe and wave overtopping at the dike crest. The high spatial resolution data show a steep increase in infragravity significant wave height in the very shallow area in front of the dike.

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 VALIDATION OF A BUOYANCY-MODIFIED TURBULENCE MODEL BY NUMERICAL SIMULATIONS OF BREAKING WAVES OVER A FIXED BAR

2018 ◽  
pp. 71
Author(s):  
Brecht Devolder ◽  
Peter Troch ◽  
Pieter Rauwoens
Keyword(s):  
Numerical Simulations ◽  
Wave Breaking ◽  
Surf Zone ◽  
Breaking Waves ◽  
Navier Stokes ◽  
Two Phase ◽  
Numerical Wave Flume ◽  
Wave Flume ◽  
Nearshore Sediment Transport ◽  
Run Up

The surf zone dynamics are governed by important processes such as turbulence generation , nearshore sediment transport , wave run-up and wave overtopping at a coastal structure. During field observations , it is very challenging to measure and quantify wave breaking turbulence . Complementary to experimental laboratory studies in a more controlled environment , numerical simulations are highly suitable to understand and quantify surf zone processes more accurately. In this study, wave propagation and wave breaking over a fixed barred beach profile is investigated using a two­ phase Navier-Stokes flow solver. We show that accurate predictions of the turbulent two-phase flow field require special attention regarding turbulence modelling. The numerical wave flume is implemented in the open­ source OpenFOAM library. The computed results (surface elevations , velocity profiles and turbulence levels) are compared against experimental measurements in a wave flume (van der A et al., 2017) .

A CFD Application of NewWave Theory to Wave-in-Deck Simulation

2016 ◽  
Vol 13 (02) ◽  
pp. 1640014 ◽  
Author(s):  
Yan Ling Wu ◽  
Graham Stewart ◽  
Yu Chen ◽  
Johan Gullman-Strand ◽  
Xin Lv ◽  
...  
Keyword(s):  
Open Source Software ◽  
Wave Theory ◽  
Numerical Approach ◽  
Air Gap ◽  
Sea Surface ◽  
Extreme Waves ◽  
Extreme Wave ◽  
Large Wave ◽  
The North ◽  
The North Sea

For existing offshore fixed platforms it is often the case that the air gap between the deck and the sea surface is not adequate and the extreme waves will encroach on the deck resulting in large wave-in-deck loads. Factors that result in inadequate air gap are seabed subsidence, sea-level increasing due to climate change and more onerous predictions of extreme crest heights. In this paper, a numerical approach based on NewWave theory [Tromans et al. (1991), Proc. 1st Int. Offshore and Polar Engineering Conf., Vol. 3, Edinburgh, UK, pp. 64–71] has been developed to represent the extreme wave conditions and implemented into the framework of an open source software, OpenFOAM, to predict the wave-in-deck loading. The results have been compared with published FLOW-3D simulations using Stoke’s 5th order wave theory for a simple box representing the Ekofisk platform deck in the Norwegian sector of the North Sea [Iwanowski et al. (2002), Proc. 21st Int. Conf. Offshore Mechanics and Artic Engineering, June 23–28, 2002, Oslo, Norway].

scholarly journals VELOCITY AND SEDIMENT CONCENTRATION FIELDS ACROSS SURF ZONES

1986 ◽  
Vol 1 (20) ◽  
pp. 79 ◽  
Author(s):  
Hans H. Dette ◽  
Klemens Uliczka
Keyword(s):  
Surf Zone ◽  
Sediment Concentration ◽  
Irregular Waves ◽  
Quasi Equilibrium ◽  
Wave Flume ◽  
Sediment Volume ◽  
Measured Profile ◽  
Induced Currents ◽  
Transport Volume ◽  
Wave Induced

Wave-induced currents and sediment concentrations in suspension across the surf zone were investigated at prototype scale in the BIG WAVE FLUME in Hannover for combined beach and dune profiles as well during the development phase until quasi-equilibrium stage as after beach equilibrium conditions had been reached. The selected initial profiles were partly investigated in repeated tests with regular and irregular waves. Based upon the obtained experimental data a comparison is presented between the measured and calculated landward displacement of sediment volume through a selected point on the beach into seaward areas. The discrepancies in between the results for measured profile change and for calculated sediment transport volume derived from vertical current and suspension distributions are discussed.

Large wave flume tests on wave-induced response of sandy seabed adjacent a water intake

2020 ◽  
Vol 195 ◽  
pp. 106709 ◽  
Author(s):  
Xiaowen Wang ◽  
Songgui Chen ◽  
Rui Wang ◽  
Jian-Min Zhang
Keyword(s):  
Water Intake ◽  
Induced Response ◽  
Large Wave ◽  
Wave Flume ◽  
Flume Tests ◽  
Wave Induced
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