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.

APPLICATION OF ACOUSTIC METHODS IN RESEARCHES OF THE BOTTOM SEDIMENT DYNAMICS

2018 ◽  
Author(s):  
Б. Дивинский ◽  
B. Divinskiy ◽  
И. Грюне ◽  
I. Gryune ◽  
Р. Косьян ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
Sediment Concentration ◽  
Irregular Waves ◽  
Single Frequency ◽  
Contactless Measurement ◽  
Measurement Means ◽  
Uniform Field ◽  
Wave Flume ◽  
Acoustic Methods ◽  
Back Scattering

Acoustic methods belong to contactless measurement means, possess high spatial and time resolution. Thus, the use of multifrequency allows directly profile both concentration and granulometric structure of the suspended substances. In 2008 in the Big Wave Flume (Hanover, Germany) by efforts of the Russian and German scientists there have been carried out the experiment on studying the bottom material suspension laws under the influence of irregular waves. The Aquascat 1000 acoustic back scattering sensor (ABS) manufactured by British company Aquatec (www.aquatecsubsea.com), equipped by a three-frequency transmitter with frequencies 1,0, 2,0 and 3,84 MHz, has been set on distance of 0,75 m from the bottom and 111 m from wave generator at the total depth of 3,2 m. Several dozen series of measurements at various parameters of surface waves have been carried out. The general picture of suspension is so that the external dynamic influence (currents, wave movements, turbulence, gravitation forces) creates a non-uniform field (gradient) of the suspended particles and in most cases due to this the average size of particles undergoes to the spatial-time variations. For this reason while defining the mass concentration of suspended sediment, using the single frequency transmitter there is necessity for numerous definition of the suspension granulometric structure what by isn’t always possible. If two and more frequencies are used the observed results comparison can give the information on average diameters of particles and on that basis the calculation of suspended sediment concentration is possibleLet's emphasize the basic advantages of back scattering acoustic gauges usage: – Obtaining the particles sizes and concentration distribution profiles is possible; – The initial granulometric structure of bottom sediments can be unknown (at use of several frequencies). The following can be referred to some lacks of the device: – The system should be calibrated in laboratory conditions; – In a positive feedback conditions the iterative computing process can converge to zero or to infinity. In this case experiments with a variation of carrier frequencies chosen for the analysis allow partially solve the problem (say experiments with different frequencies pairs, as 2/1 of MHz or 4/2 MHz).

scholarly journals HYDRODYNAMICS UNDER LARGE-SCALE REGULAR AND BICHROMATIC BREAKING WAVES

2018 ◽  
pp. 90
Author(s):  
Dominic Van der A ◽  
Joep Van der Zanden ◽  
Ming Li ◽  
James Cooper ◽  
Simon Clark ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Surf Zone ◽  
Experimental Studies ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Small Scale ◽  
Breaking Wave ◽  
Wave Flume ◽  
Cfd Models

Multiphase CFD models recently have proved promising in modelling cross‐shore sediment transport and morphodynamics (Jacobsen et al 2014). However, modelling breaking wave turbulence remains a major challenge for these models, because it occurs at very different spatial and temporal length scales and involves the interaction between surface generated turbulence and turbulence generated in the bottom boundary layer. To an extent these challenges arise from a lack of appropriate experimental data, since most previous experimental studies involved breaking waves at small-scale, and have not permitted investigation of the turbulent boundary layer processes. Moreover, most existing studies have concentrated on regular waves, thereby excluding the flow and turbulence dynamics occurring at wave group time-scales under irregular waves within the surf zone. These limitations motivated a new experiment in the large-scale CIEM wave flume in Barcelona involving regular and irregular waves. The experiment was conducted in May-July 2017 within the HYDRALAB+ Transnational Access project HYBRID.

scholarly journals Wave-Induced Distribution of Microplastic in the Surf Zone

2020 ◽  
Vol 7 ◽  
Author(s):  
Nils B. Kerpen ◽  
Torsten Schlurmann ◽  
Alexander Schendel ◽  
Jannek Gundlach ◽  
Daniel Marquard ◽  
...  
Keyword(s):  
Surf Zone ◽  
Vertical Direction ◽  
Accumulation Point ◽  
Shallow Waters ◽  
Regular Waves ◽  
Wave Flume ◽  
Particle Parameter ◽  
Run Up ◽  
Sloping Beach ◽  
Wave Induced

In this study, the wave-induced distribution of 13 microplastic (MP) samples of different size, shape, and density was investigated in a wave flume with a sandy mobile beach bed profile. The particle parameter were chosen based on an occurrence probability investigated from the field. MP abundances were analyzed in cross-shore and vertical direction of the test area after over 40,000 regular waves. It was found, that MP particles accumulated in more shallow waters with increasing size and density. Particles with high density (ρs>1.25 g/cm3) have been partly confined into deeper layers of the sloping beach during the formation of the bed profile. Particles with a density lower than that of water used in the experiments floated constantly in the surf zone or deposited on the beach caused by wave run-up. A correlation was found between the settling velocity of the MP particles and the flow velocity at the accumulation point and a power function equation developed. The obtained results were critically discussed with findings from the field and further laboratory studies.

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 A Numerical Model of the Wave-Induced Currents in the Turbulent Coastal Zone

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
O. Fahmy ◽  
K. M. Fassieh ◽  
M. A. Zaki
Keyword(s):  
Numerical Model ◽  
Water Waves ◽  
Surf Zone ◽  
Nonlinear Partial Differential Equations ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Coastal Protection ◽  
Protection Measures ◽  
Induced Currents ◽  
Wave Induced

A numerical model is developed, validated and applied to the turbulent coastal currents. The currents are driven by the sea surface slope and the radiation stresses of water waves. They are resisted by friction due to turbulent eddies and sea bottom. The k-ε model is used to model the turbulent stresses. Five simultaneous nonlinear partial differential equations govern the depth-averaged dynamics in the surf zone. An implicit finite-difference scheme is used to obtain an accurate numerical solution of the resulting initial-boundary value problem. It is tested against the case of straight coast with uniform bottom slope and a protective jetty. To investigate the actual wave-induced currents, the model is applied to simulate the currents for three real case studies. Results show that the model could be used to compute currents caused by the constructing coastal protection measures and could predict the locations of accretion and scouring.

scholarly journals Quasi-2DV Circulation Model of Wave-induced Currents in the Surf Zone

1997 ◽  
Vol 13 ◽  
pp. 543-548
Author(s):  
Masamitsu Kuroiwa ◽  
Hideaki Noda ◽  
Yasuyuki Houchi
Keyword(s):  
Surf Zone ◽  
Circulation Model ◽  
Induced Currents ◽  
Wave Induced

scholarly journals Microelectrode Velocity Effects and Aquatic Eddy Covariance Measurements under Waves

2016 ◽  
Vol 33 (2) ◽  
pp. 263-282 ◽  
Author(s):  
Clare E. Reimers ◽  
H. Tuba Özkan-Haller ◽  
Andrea T. Albright ◽  
Peter Berg
Keyword(s):  
Eddy Covariance ◽  
Irregular Waves ◽  
Velocity Measurements ◽  
Large Wave ◽  
Wave Flume ◽  
Eddy Covariance Measurements ◽  
Average Flux ◽  
Series Of Experiments ◽  
Wave Induced ◽  
Oxygen Measurements

AbstractInterest in validating the eddy covariance (EC) technique under wave-induced flows led to a series of experiments in a 104-m-long large wave flume (LWF) using an acoustic Doppler velocimeter (ADV) and two oxygen microelectrodes (tips ~2 mm apart) mounted on a sturdy tripod. Four additional ADVs positioned within the flume provided comparative near-bed velocity measurements during experiments with irregular waves over a sand bed. These measurements revealed that modifications of local turbulence by the tripod frame were insignificant. However, errors in velocity measurements were at times observed for setups where the microelectrode tips protruded into the ADV’s measurement volume. Disparate oxygen microelectrode velocity effects (stirring sensitivities) combined with response time offsets were also identified as problems, adding biases to EC flux derivations. Microelectrode velocity effects were further investigated through modeling designed to mimic the LWF data, and through examination of a 12-h dataset from the Oregon shelf. The modeling showed that under progressive waves, an artificial EC flux, or bias, arises most severely when the velocity sensitivity of the microelectrode is unequal in opposing flow directions or augmented by horizontal currents, and the velocity and oxygen data are not perfectly aligned in time. Sensitivities to wave motions were seen in the oxygen measurements from the Oregon shelf, contributing to an average flux of +2.7 ± 0.6 mmol m−2 day−1 (SE, n = 22) at wave frequencies. Since overall EC fluxes equaled only −4.1 ± 1.8 mmol m−2 day−1 (SE, n = 22), sources of EC biasing coupled to waves cannot be ruled out as potential problems for estimating exact benthic oxygen fluxes under common continental shelf field conditions.

scholarly journals SUSPENDED AND BEDLOAD TRANSPORT IN THE SURF ZONE: IMPLICATIONS FOR SAND TRANSPORT MODELS

2017 ◽  
pp. 30 ◽  
Author(s):  
Joep van der Zanden ◽  
Dominic A. Van der A ◽  
Tom O'Donoghue ◽  
David Hurther ◽  
Ivan Caceres ◽  
...  
Keyword(s):  
Large Scale ◽  
Surf Zone ◽  
Sediment Concentration ◽  
Breaking Waves ◽  
Bedload Transport ◽  
Transport Processes ◽  
Sand Transport ◽  
Wave Flume ◽  
Load Transport ◽  
Particle Velocities

This paper presents results obtained during a large-scale wave flume experiment focused at measuring hydrodynamics and sediment transport processes in the wave breaking region. The experiment involved monochromatic plunging breaking waves over a mobile bed barred profile consisting of D50 = 0.24 mm sand. Vertical profiles of velocity, turbulence, sand concentration and sand fluxes were measured at 12 cross-shore locations, covering the shoaling region up to the inner surf zone. Particularly high-resolution profiles were obtained near the bed within the wave bottom boundary layer, using an acoustic sediment concentration and velocity profiler (ACVP). Sheet flow concentration and particle velocities were measured at two locations near the bar crest using two conductivity-based concentration measurement tanks (CCM+). Total transport rates, obtained from the evolving bed profile measurements, were decomposed into suspended and bedload transport contributions across the bar. The present paper presents a summary of the key findings of the experiment, which are used to discuss existing approaches for modeling suspended and bed load transport in the surf zone.

Sign in / Sign up

Export Citation Format

Share Document