A Computer-Based Electro-Optical System for Measuring Wave-Induced Sand Concentrations

1972 ◽  
Vol 94 (2) ◽  
pp. 429-433
Author(s):  
J. R. Glover ◽  
F. A. Locher ◽  
P. K. Bhattacharya
Keyword(s):  
Sediment Concentration ◽  
Breaking Waves ◽  
Average Concentration ◽  
Random Component ◽  
Oscilloscope Trace ◽  
Chart Recorder ◽  
Signal Characteristics ◽  
Wave Cycle ◽  
Computer Based ◽  
Wave Induced

A computer-based system utilizing an electro-optical instrument has been developed for generating and processing a signal proportional to the instantaneous sand concentration at a point in a flow field. Herein are described the instrumentation and techniques used in a study of sediment entrainment by periodic waves breaking on sand beaches. The instantaneous sediment concentration has been decomposed as follows: C(x,y,z,t)=C¯(x,y,z)+C′(x,y,z,t)+Cp(x,y,z,t) where C(x, y, z) is the temporal average concentration, C′(x, y, z, t) is a random component of the sediment concentration, and Cp(x, y, z, t) is a repetitive component with period equal to the period of the breaking waves. Particular attention has been given to isolating the repetitive component which was so obscured by the signal characteristics that no periodicity was apparent on either an oscilloscope trace or a strip chart recorder. Spectral analysis was not applicable because the shape of the repetitive waveform, Cp(x, y, z, t), over one wave cycle was desired.

scholarly journals SURF ZONE MEASUREMENTS OF SUSPENDED SEDIMENT

1978 ◽  
Vol 1 (16) ◽  
pp. 104 ◽  
Author(s):  
Timothy W. Kana
Keyword(s):  
South Carolina ◽  
Suspended Sediment ◽  
Surf Zone ◽  
Sediment Concentration ◽  
Breaking Waves ◽  
Bulk Water ◽  
Scatter Plots ◽  
Water Volumes ◽  
Spilling Breakers

Suspended sediment concentration was measured in approximately 250 breaking waves on undeveloped beaches near Price Inlet, South Carolina, U.S.A., using portable in situ bulk water samplers. As many as 10 instantaneous 2-liter water volumes were obtained in each wave for a total of 1500 samples. Concentrations of suspended sediment were determined at fixed intervals of 10, 30, 60 and 100 cm above the bed for various surf zone positions relative to the breakpoint. The majority of waves sampled during 22 days in June and July, 1977 were relatively long crested, smooth, spilling to plunging in form, with breaker heights ranging from 20 to 150 cm. Surf zone process variables measured included breaker height and depth, breaker type, wave period, surface longshore current velocity, wind velocity and direction. Scatter plots of mean concentration against various process parameters indicate the amount of sediment entrained in breaking waves is primarily a function of elevation above the bed, breaker type, breaker height and distance from the breakpoint. Concentration ranged over 3 orders of magnitude up to 10 gm/1, but varied less than 1 order for samples collected under similar conditions with regard to elevation and breaker type. Plunging breakers generally entrain 1 order more sediment than spilling breakers equal in height. Despite considerable scatter, these data indicate concentration decreases with increasing wave height for waves 50 to 150 cm high, suggesting that small waves can be important in the transport of sand on gently-sloping open coasts.

scholarly journals WAVE-INDUCED SHOCK PRESSURES UNDER REAL SEA STATE CONDITIONS

1988 ◽  
Vol 1 (21) ◽  
pp. 173 ◽  
Author(s):  
Joachim Grune
Keyword(s):  
Peak Pressure ◽  
Field Measurements ◽  
Breaking Waves ◽  
Sea State ◽  
Pressure Time ◽  
Time Histories ◽  
Wave Induced

This paper deals with a study on shock pressures, which occur on sloping seadykes and revetments due to breaking waves. Results from field measurements are presented with respect to peak pressure values as well as to characteristics of pressure-time histories.

Experimental Study on Regular Wave-Induced Scour and Settlement of a Submerged Obstacle Upon a Fluidized Sandbed

2010 ◽  
Author(s):  
Shiaw-Yih Tzang ◽  
Yung-Lung Chen ◽  
Shan-Hwei Ou
Keyword(s):  
Fluidized Beds ◽  
Suspended Sediment Concentration ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Regular Waves ◽  
Rf Test ◽  
Total Settlement ◽  
Test Soil ◽  
Rectangular Obstacle ◽  
Wave Induced

Bed scouring and structure settlement due to interactions of regular waves and a submerged rectangular obstacle in the shallow water regions upon a fluidized fine sandy bed are experimentally investigated. Both impervious and pervious structures are installed on the test soil bed and synchronous measurements of water surface, bed surface, suspended sediment concentration and pore pressures are carried out at locations upstream and downstream. The measurements illustrate that interactions between waves and structures have relatively mild affects on the bed scouring in an unfluidized response. The interactions become more intense in the fluidized responses with significant wave decay over and increasing suspended sediments near above the fluidized beds oscillating with similar period to the loading waves. Meanwhile, the submerged structure starts to settle into the fluidized bed and significant scouring occurs. The interactions are typically greater in a RF test than in a NRF test. More than 90% of the total settlement occurs in a single event of the RF response so that the impervious and pervious structures become half buried and totally buried after the event. The settlements further affect the interactions of following loading waves and the fluidized beds. As a result, scouring on both sides of the half buried impervious obstacle is greater than those of the totally buried pervious structure.

scholarly journals AN EVALUATION OF SUSPENDED SEDIMENT CONCENTRATION MODELS UNDER BREAKING WAVES

2018 ◽  
pp. 42
Author(s):  
Gabriel Lim ◽  
Ravindra Jayaratne ◽  
Tomoya Shibayama
Keyword(s):  
Kinetic Energy ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Critical Evaluation ◽  
Sediment Concentration ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Wave Conditions ◽  
Improved Accuracy ◽  
Bed Friction

Implementing the effects of turbulent kinetic energy (TKE) is essential in producing accurate suspended sediment concentration (SSC) models, especially under breaking wave conditions. SSC is commonly attributed to two different turbulent sources under breaking wave conditions: 1) bed-friction and 2) breaking-induced turbulent vortices. Numerous studies have endeavoured to quantify the effects of TKE and incorporate them into SSC models. To name a few: Mocke & Smith (1992, henceforth MS92), Shibayama & Rattanapitikon (1993, henceforth SR93), Jayaratne & Shibayama (2007, henceforth JS07), and Yoon et al. (2015, henceforth Y15). The present study evaluates these 4 existing SSC models and validates them against recently published datasets from the ‘CROSSTEX’ (Yoon & Cox, 2010), ‘SandT-Pro’ (Ribberink et al., 2014) and ‘SINBAD’ (vdZ et al. 2015) projects. Following critical evaluation, suggestions are made to enhance existing SSC models, and these findings are then incorporated into producing two new SSC models that indicate improved accuracy.

scholarly journals WAVE-INDUCED FLOW AND NEARSHORE SUSPENDED SEDIMENT

1988 ◽  
Vol 1 (21) ◽  
pp. 108 ◽  
Author(s):  
J.C. Doering ◽  
A.J. Bowen
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Accurate Prediction ◽  
Wave Crest ◽  
Wave Trough ◽  
Induced Flow ◽  
Wave Induced ◽  
Velocity Skewness

It has been realized for nearly one hundred years that the transport of sediment is related to the characteristics of a wave, in particular its shape. Cornish (1898) noticed that the shoreward velocity associated with a wave crest was more effective at moving coarse sediment than was the seaward velocity associated with the wave trough. Cornish's observation was consistent with the theory of Stokes (1847), which predicts the onshore velocity associated with the wave crest is stronger and of shorter duration than the offshore velocity associated with the wave trough. This horizontal asymmetry of the cross-shore flow, which is a reflection of the wave shape, is known as velocity skewness. It has been suggested that "the existence of the beach depends on small departures from symmetry in the velocity field balancing the tendency for gravity to move material offshore"(Bowen, 1980). Although the concept of velocity skewness has been incorporated into detailed predictors of sediment transport (Bowen, 1980; Bailard and Inman, 1981) it is only one of many facets that needs to be understood in order to make the accurate prediction of sediment transport realizable. A comprehension of sediment transport is hampered by both an incomplete knowledge of the hydrodynamics and a lack of instrumentation to directly measure instantaneous sediment concentration and the accurate prediction of sediment transport is probably the most enigmatic problem in coastal engineering. Occasionally, suspended sediment concentration has been inferred from in situ pumps and hand-held tubes, but these methods lack the temporal and spatial resolution necessary to elucidate the details of the interaction between the waveinduced flow and the sediment. Recently, a miniature optical backscatter sensor (MOBS), which provides a time series of suspended sediment concentration at a "point", was developed by Downing et al. (1981). During a recent field experiment a vertical array of 5 of these optical backscatter sensors and a colocated flow meter was deployed close to the sea bed. These colocated measurements provide a unique opportunity to investigate the response of near-bed suspended sediment concentration to the wave-induced flow.

Two-Dimensional Model for Wave-Induced Pore Pressure Accumulation in Marine Sediments

2013 ◽  
Author(s):  
Hongyi Zhao ◽  
Dong-Sheng Jeng ◽  
Huijie Zhang ◽  
Jisheng Zhang
Keyword(s):  
Pore Pressure ◽  
Marine Sediments ◽  
Wave Motion ◽  
Present Model ◽  
Two Dimensional ◽  
New Model ◽  
One Dimensional ◽  
Wave Cycle ◽  
Previous Solution ◽  
Wave Induced

In this paper, a two-dimensional (2D) porous model is established to investigate the predication of the wave-induced pore pressure accumulations in marine sediments. In the new model, the VARANS equation is used as the governing equation for the wave motion, while the Biot’s consolidation theory is used for porous seabed. The present model is verified with the previous experimental data [1] and provides a better prediction of pore pressure accumulation than the previous solution [2]. With the new model, a 2D liquefied zone is formed at the beginning of the process, and then gradually move down. After a certain wave cycle (for example, 30 wave cycles in the numerical example), the liquefaction zone will become one-dimensional (1D) and continuously move down and eventually approaches to a constant. Numerical results also conclude the maximum liquefaction depth increases as wave height increases and in shallow water.

The Spatiotemporal Variations of Suspended Sediment Concentration in Le’an River Catchment of Poyang Lake Basin

2012 ◽  
Vol 610-613 ◽  
pp. 1099-1102 ◽  
Author(s):  
Zhen Wang ◽  
Qi Zhang ◽  
Xiu Li Xu ◽  
Hai Ying Gao
Keyword(s):  
Suspended Sediment ◽  
Poyang Lake ◽  
Arable Land ◽  
Sediment Concentration ◽  
Average Concentration ◽  
Lake Basin ◽  
Rainfall Events ◽  
River Catchment ◽  
Poyang Lake Basin ◽  
Different Seasons

Suspended sediment (SS) is one of the important parameters quantifying the degree of water pollution. In order to explore the spatiotemporal variation of the SS in Le’an river catchment, an important sub-catchment of Poyang lake basin, a total of 17 sampling points at rivers were selected for observations. Results show that, the concentration of SS is quite different across the catchment. The average concentration of SS in the upstream of the catchment with forest as the dominant land use, is 6.92mg/L, while the concentration in the downstream with a certain percentage of arable land is 14.39mg/L. The SS concentration shows an increasing trend from the upstream to the downstream, in correlation with the change of land uses. Also there exists a considerable deviation of the SS concentration in different seasons. The concentration in summer is relatively high, while lower in other seasons, with a likely relationship to rainfall events.

Wave induced sediment concentration in weak current fields

1992 ◽  
Vol 30 (5) ◽  
pp. 623-638
Author(s):  
M. Mokhi Es Abou-Seida ◽  
Jen-Men Lo ◽  
M. A. Muralidhar
Keyword(s):  
Sediment Concentration ◽  
Weak Current ◽  
Wave Induced
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