scholarly journals BEACH PROFILES AND ON-OFFSHORE SEDIMENT TRANSPORT

1980 ◽  
Vol 1 (17) ◽  
pp. 67 ◽  
Author(s):  
Akira Watanabe ◽  
Yoshihiko Riho ◽  
Kiyoshi Horikawa
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Laboratory Test ◽  
Test Data ◽  
Critical Shear Stress ◽  
Two Dimensional ◽  
Bottom Shear Stress ◽  
Beach Profile ◽  
Profile Changes ◽  
Sloping Beach

The on-offshore sediment transport due to waves on a sloping beach is studied by analyzing the laboratory test data on two-dimensional beach deformation. The net rates of sediment transport both inside and outside the breaker zone are evaluated from beach profile changes and are related to the nondimensional bottom shear stress or the Shields parameter. The importance of the critical shear stress and of asymmetrical to-and-fro water partical motion near the bottom is pointed out.

scholarly journals Two-dimensional numerical simulation of sediment transport using improved critical shear stress methods

2020 ◽  
Vol 35 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Zhiyong Feng ◽  
Guangming Tan ◽  
Junqiang Xia ◽  
Caiwen Shu ◽  
Peng Chen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Shear Stress ◽  
Sediment Transport ◽  
Critical Shear Stress ◽  
Two Dimensional

scholarly journals SEDIMENT TRANSPORT AND BEACH TRANSFORMATION

1982 ◽  
Vol 1 (18) ◽  
pp. 88 ◽  
Author(s):  
Tomoya Shibayama ◽  
Kiyoshi Horikawa
Keyword(s):  
Sediment Transport ◽  
Wave Motion ◽  
Wave Theory ◽  
Linear Wave ◽  
Two Dimensional ◽  
Beach Profile ◽  
Field Investigations ◽  
Transport Calculation ◽  
Profile Changes ◽  
Profile Change

Laboratory and field investigations were performed in order to formulate a predictive model of two-dimensional beach profile change. The observed transport was classified into six types, and transport formulas were deduced for each type based on a microscale description of sediment movement caused by wave action. A numerical model of two-dimensional beach transformation was then developed. Beach profile changes calculated with the model were then compared with the laboratory results. The model was found to give reasonable results except in the vicinity of the wave plunging point. The sediment transport calculation is based on a sinusoidal velocity profile. The model appeares to give good results as long as the wave motion can be reasonably approximated by linear wave theory.

scholarly journals EXPERIMENTS ON BEACH PROFILE CHANGE WITH A LARGE WAVE FLUME

1982 ◽  
Vol 1 (18) ◽  
pp. 85 ◽  
Author(s):  
Ryoichi Kajima ◽  
Takao Shimizu ◽  
Kohki Maruyama ◽  
Shozo Saito
Keyword(s):  
Simple Model ◽  
Transport Rate ◽  
Sand Transport ◽  
Two Dimensional ◽  
Beach Profile ◽  
Large Wave ◽  
Wave Flume ◽  
Grain Sizes ◽  
Profile Changes ◽  
Profile Change

Two-dimensional beach profile changes were investigated with a newly constructed prototype-scale wave flume. The flume is 205 m long, 3.4 m wide and 6 m deep. Sand of two grain sizes was used in the experiments. Analysis of the results was made through use of the parameter C, introduced by Sunamura and Horikawa (1974) to classify beaches as either erosional and accretionary. Beach profile changes obtained in the flume were similar to those in the prototype (field). Net sand transport rate distributions were classified into five types, two of which do not seem to have been observed in laboratory (smallscale) experiments. A simple model describing the five types was developed for evaluating two-dimensional beach profile changes.

scholarly journals Bed Shear Stress Influence on Local Scour Geometry Properties in Various Flume Development Conditions

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2346 ◽  
Author(s):  
Kiraga ◽  
Popek
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Mutual Influence ◽  
Three Dimensional ◽  
Critical Shear Stress ◽  
Water Structure ◽  
Correlation Coefficients ◽  
Bed Shear Stress ◽  
Hole Dimensions ◽  
Bed Material

Numerous approaches in sediment mobility studies highlighted the key meaning of channel roughness, which results not only from bed material granulation but also from various bed forms presence, caused by continuous sediment transport. Those forms are strictly connected with the intensity of particle transport, and they eventuate from bed shear stress. The present paper comprised of local scours geometric dimensions research in three variants of lengthwise development of laboratory flume in various hydraulic properties, both in “clear-water” and “live-bed” conditions of sediment movement. Lots of measurements of the bed conformation were executed using the LiDAR device, marked by a very precise three-dimensional shape description. The influence of the bed shear stress downstream model on scours hole dimensions of water structure was investigated as one of the key factors that impact the sediment transport intensity. A significant database of 39 experimental series, lasting averagely 8 hours, was a foundation for delineating functional correlations between bed shear stress-and-critical shear stress ratio and geometry properties of local scours in various flume development cases. In the scope of mutual influence of bed shear stress and water depth, high correlation coefficients were attained, indicating very good and good functional correlations. Also, the influence of bed shear stress and the total length of the scour demonstrated a high correlation coefficient.

scholarly journals THREE DIMENSIONAL TESTS ON DYNAMIC EQUILIBRIUM AND ARTIFICIAL NOURISHMENT

1976 ◽  
Vol 1 (15) ◽  
pp. 89 ◽  
Author(s):  
J.W. Kamphuis ◽  
R.M. Myers
Keyword(s):  
Shear Stress ◽  
Dynamic Equilibrium ◽  
Three Dimensional ◽  
Critical Shear Stress ◽  
Two Dimensional ◽  
Dimensional Facility ◽  
Trap Location ◽  
Artificial Nourishment ◽  
Reflection Of Waves

A three dimensional facility for testing dynamic equilibrium and artificial nourishment of beaches was developed. Specific conclusions are drawn with respect to trap location and re-reflection of waves. It was found that dynamic equilibrium is achieved faster in three dimensional tests than in previous two dimensional work and that the profiles are eroding profiles rather than potential (limit) profiles. It was seen that profiles develop around the offshore bar which is shaped early in the experiments. Also the depth of the summer step was found predictable from critical shear stress considerations. Finally, onshore nourishment of eroding beaches was found to be successful.

scholarly journals SUBGRID MODELLING IN DEPTH INTEGRATED FLOWS

1988 ◽  
Vol 1 (21) ◽  
pp. 35 ◽  
Author(s):  
P.A. Madsen ◽  
M. Rugbjerg ◽  
I.R. Warren
Keyword(s):  
Shear Stress ◽  
Large Scale ◽  
Eddy Viscosity ◽  
Grid Size ◽  
Coastal Engineering ◽  
Shear Stresses ◽  
Two Dimensional ◽  
Bottom Shear Stress ◽  
Hydrodynamic Simulations ◽  
Engineering Studies

Hydrodynamic simulations in coastal engineering studies are still most commonly carried out using two-dimensional vertically integrated mathematical models. As yet, threedimensional models are too expensive to be put into general use. However, the tendency with 2-D models is to use finer and finer resolution so that it becomes necessary to include approximations to some 3-D phenomena. It has been shown by many authors that simulations of large scale eddies can be quite realistic in 2-D models (c.f. Abbott et al. 1985). Basically there exists two different mechanisms of circulation generation. The first one is based on a balance between horizontally and grid-resolved momentum transfers and the bed resistance - i.e. a balance between the convective momentum terms and the bottom shear stress. The second one is due to momentum transfers that are not resolved at the grid scale but appears instead as horizontally distributed shear stresses. In many practical situations the circulations will be governed by the first mechanism. This is the case if the diameter of the circulation and the grid size is much larger than the water depth. In this situation the eddies are friction dominated so that the effect of sub-grid eddy viscosity is limited. In this case 2-D models are known to produce very realistic results and several comparisons with measurements have been reported in the literature.

Controls on sediment transport in semi-alluvial boulder-bed streams—implications for restoration of spawning gravel

2020 ◽  
Author(s):  
Lina Polvi
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Critical Shear Stress ◽  
Field Research ◽  
Tracer Experiment ◽  
Transport Processes ◽  
Mountain Streams ◽  
Northern Fennoscandia ◽  
Transport Distance ◽  
Individual Grains

<p>Many streams in northern Fennoscandia are considered semi-alluvial in that they contain abundant coarse sediment (cobbles and boulders) deposited during continental glaciation in the form of moraines, eskers, and erratics. These streams contain sensitive trout and salmon populations, and restoration efforts (after channelization from over a century of timber-floating) strive to re-create essential habitat and spawning beds. However, little is known about controls on sediment transport processes in boulder-bed streams that can affect both channel evolution and restoration of spawning gravel. Prior flume and field research of boulder-bed channels in mountainous areas show that boulder protrusion and proximity can alter critical shear stress; however, in contrast to mountain streams, boulder-bed channels in northern Fennoscandia have relatively low bed slopes (S<sub>0</sub>: 0.5-6%) and low-magnitude flow regimes (buffered by upstream lakes).</p><p>In order to determine controls on gravel and cobble sediment transport in semi-alluvial boulder-bed streams, a sediment tracer experiment was conducted in the Vindel River catchment in northern Sweden. Approximately 1500 tracer clasts (b-axis: 2.5-15 cm), with imbedded RFID tags, were placed in five stream reaches (121-556 per reach) with a range of channel slopes (S<sub>0</sub>: ~2-6%), boulder densities, and degrees of protrusion. The geometry of each tracer clast (a-, b-, and c-axes) was quantified, and the location of each tracer clast was surveyed with a total station in the summers of 2017, 2018, and 2019. Both the morphologic setting (e.g., step, pool, riffle, backwater, directly above/below boulder) and constrainment class (e.g., unconstrained, shielded, imbricated, buried) were classified for each tracer at each survey occasion. There was a 80-90% recovery rate of tracer clasts; despite several reaches experiencing >Q<sub>50</sub> snowmelt flood, the median transport distance for D<sub>10</sub>- to D<sub>50 </sub>clasts was ~0.1 m. Preliminary analyses showed large variation in particle-size thresholds for entrainment and relationships with transport distance within and among reaches. There was no clear relationship between local bed slope or calculated bankfull shear stress and transport distance. Differences in entrainment and transport distances among reaches was controlled by boulder density and protrusion, which likely increase grain resistance and thus critical shear stress, reducing sediment transport (as shown by previous studies in boulder-bed mountain streams). Factors negatively affecting sediment transport include shielding, proximity to boulders, and certain morphologic settings (e.g., backwaters and pools). Variability was too high to allow confident prediction of entrainment of individual grains; however, based on these results and observations, some general guidelines for stream restoration of spawning gravel in semi-alluvial boulder-bed channels are presented.      </p>

scholarly journals ANALISIS ANGKUTAN SEDIMEN DASAR (BED LOAD) PADA SALURAN IRIGASI MATARAM YOGYAKARTA

Teknisia ◽  
2021 ◽  
Vol XXVI (1) ◽  
Author(s):  
Anggi Hermawan ◽  
◽  
Erwin Afiato ◽  
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Froude Number ◽  
Critical Shear Stress ◽  
Bed Load ◽  
Cross Sectional ◽  
Logarithmic Curve ◽  
Agricultural Areas ◽  
The Relationship ◽  
Downstream Area

In the last decade, the problem that has occurred in the Yogyakarta Mataram irrigation channel is the occurrence of sedimentation in the channel. This has an impact on reducing the cross-sectional discharge capacity of the canal and resulting in the supply of irrigation discharge to agricultural areas to be not optimal, so that agricultural productivity in the Mataram Irrigation Area will also not be optimal. The sediment transport (bed load) that occurs in an open channel can be approached using the empirical equation, including the Einstein, Meyer - Peter Muller and Frijlink equations. Sediment transport events that occur in the channel are stated based on the magnitude of the flow shear stress which exceeds the critical shear stress of the sediment particles. The quantity of sediment transport in the channel is stated on the logarithmic curve of the relationship between the froude number (fr) to the sediment transports (qb). The Curve explains that the increase in the froude number (fr) that occurs on each section of the channel will be directly proportional to the increase in the quantity of transport sediment (qb). The largest sediment transport occurred at the site of the Gambang and Nambongan channel section with a prediction of sediment transport of 3.57 m3/day and 3.67 m3/day, respectively. Thus, the potential for sediment transport that will settle in the downstream area is 3.67 m3/day.

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