scholarly journals MAGNITUDE OF THE B-FACTOR UNDER WAVE ACTION

1986 ◽  
Vol 1 (20) ◽  
pp. 67
Author(s):  
J. Van de Graaff ◽  
R.C. Steijn
Keyword(s):  
Velocity Distribution ◽  
Water Depth ◽  
Sediment Concentration ◽  
Wave Action ◽  
Practical Applications ◽  
Wave Flume ◽  
Sediment Size ◽  
Flume Tests ◽  
Waves And Currents ◽  
The Moment

The sediment transport due to waves and currents depends on the distribution of sediment concentration and on the distribution of the velocity over the water depth. Our knowledge of both phenomena for practical applications is still rather poor. Some results of wave flume tests concerning the distribution of sediment concentrations due to wave action will be discussed. It turns out that the sediment size of the bottom material has a rather unexpected effect hereupon. With respect to the velocity distribution only some qualitative remarks can be made at the moment.

scholarly journals Critical conditions of bed sediment entrainment due to debris flow

2004 ◽  
Vol 4 (3) ◽  
pp. 469-474 ◽  
Author(s):  
M. Papa ◽  
S. Egashira ◽  
T. Itoh
Keyword(s):  
Shear Stress ◽  
Debris Flow ◽  
Erosion Rate ◽  
Sediment Concentration ◽  
Critical Conditions ◽  
Bed Shear Stress ◽  
Bed Sediment ◽  
Sediment Size ◽  
Flume Tests ◽  
Sediment Entrainment

Abstract. The present study describes entrainment characteristics of bed material into debris flow, based on flume tests, numerical and dimensional analyses. Flume tests are conducted to investigate influences of bed sediment size on erosion rate by supplying debris flows having unsaturated sediment concentration over erodible beds. Experimental results show that the erosion rate decreases monotonically with increase of sediment size, although erosion rate changes with sediment concentration of debris flow body. In order to evaluate critical condition of bed sediment entrainment, a length scale which measures an effective bed shear stress is introduced. The effective bed shear stress is defined as total shear stress minus yield stress on the bed surface. The results show that critical entrainment conditions can be evaluated well in terms of Shields curve using the effective bed shear stress instead of a usual bed shear stress.

SAND CONCENTRATION IN AN OSCILLATOR! FLOW

1974 ◽  
Vol 1 (14) ◽  
pp. 66 ◽  
Author(s):  
W.T. Bakker
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Velocity Distribution ◽  
Suspended Sediment ◽  
Oscillatory Flow ◽  
Sediment Concentration ◽  
Suspended Sediment Transport ◽  
Bed Load ◽  
Velocity Gradients ◽  
The Moment

In this paper first a numerical model is described concerning the velocity distribution in an oscillatory flow, respectively without and with resultant current . From the momentaneous velocity gradients eddy viscosities are derived . Using the approach of VANONI [13 , a numerical model is given for the calculation of sediment concentration and suspended sediment transport. In order to give reliable results, the bed-load concentration should be known This will be investigated in the future; at the moment the model only provides qualitative results.

scholarly journals A STUDY ON WAVE-INDUCED PARTICLE VELOCITIES IN FLUID MUD LAYER

2017 ◽  
pp. 28
Author(s):  
Mohsen Soltanpour ◽  
Hadi Shamsnia ◽  
Tomaya Shibayama ◽  
Ryota Nakamura ◽  
Akifumi Tatekoji
Keyword(s):  
Fine Particles ◽  
Wave Attenuation ◽  
Wave Action ◽  
Fluid Mud ◽  
Coastal Zones ◽  
Wave Flume ◽  
Waves And Currents ◽  
Particle Velocities ◽  
Wave Induced ◽  
The Waves

Cohesive sediments can be found in many coastal zones all over the world. The upper layer of these muddy coasts may be fluidized under the wave action. Fluid mud is also formed by settlement of fine particles when the waves and currents exert a small shearing stress on the bed. When the waves pass over the fluid mud layer, it absorbs wave energy and, in turn, moves due to the wave action. The present study offers a numerical and experimental study of wave-mud interaction on a horizontal bed. A number of wave flume laboratory tests are presented to investigate wave attenuation, particle velocities in fluid mud layer and mud mass transport under different wave characteristics. The laboratory results are also compared with a developed semi-analytical model.

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 Getting information on suspended sediments in a large river from acoustic backscatter

2018 ◽  
Vol 40 ◽  
pp. 04017
Author(s):  
Adrien Vergne ◽  
Céline Berni ◽  
Jérôme Le Coz
Keyword(s):  
Suspended Sediment Concentration ◽  
Spatial Information ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Large River ◽  
Acoustic Backscatter ◽  
Qualitative Information ◽  
Sediment Size ◽  
The Common

There has been a growing interest in the last decade in extracting information on Suspended Sediment Concentration (SSC) from acoustic backscatter in rivers. Quantitative techniques are not yet effective, but acoustic backscatter already provides qualitative information on suspended sediments. In particular, in the common case of a bi-modal sediment size distribution, corrected acoustic backscatter can be used to look for sand particles in suspension and provide spatial information on their distribution throughout a river crosssection. This paper presents a case-study where these techniques have been applied.

scholarly journals Large-Scale Laboratory Experiments on Mussel Dropper Lines in Ocean Surface Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 29
Author(s):  
Rebekka Gieschen ◽  
Christian Schwartpaul ◽  
Jannis Landmann ◽  
Lukas Fröhling ◽  
Arndt Hildebrandt ◽  
...  
Keyword(s):  
Large Scale ◽  
Laboratory Experiments ◽  
Blue Mussel ◽  
Farming Systems ◽  
Quality Parameter ◽  
Large Wave ◽  
Marine Aquaculture ◽  
Ocean Surface Waves ◽  
Wave Flume ◽  
Waves And Currents

The rapid growth of marine aquaculture around the world accentuates issues of sustainability and environmental impacts of large-scale farming systems. One potential mitigation strategy is to relocate to more energetic offshore locations. However, research regarding the forces which waves and currents impose on aquaculture structures in such conditions is still scarce. The present study aimed at extending the knowledge related to live blue mussels (Mytilus edulis), cultivated on dropper lines, by unique, large-scale laboratory experiments in the Large Wave Flume of the Coastal Research Center in Hannover, Germany. Nine-months-old live dropper lines and a surrogate of 2.0 m length each are exposed to regular waves with wave heights between 0.2 and 1.0 m and periods between 1.5 and 8.0 s. Force time histories are recorded to investigate the inertia and drag characteristics of live mussel and surrogate dropper lines. The surrogate dropper line was developed from 3D scans of blue mussel dropper lines, using the surface descriptor Abbott–Firestone Curve as quality parameter. Pull-off tests of individual mussels are conducted that reveal maximum attachment strength ranges of 0.48 to 10.55 N for mussels that had medium 3.04 cm length, 1.60 cm height and 1.25 cm width. Mean drag coefficients of CD = 3.9 were found for live blue mussel lines and CD = 3.4 for the surrogate model, for conditions of Keulegan–Carpenter number (KC) 10 to 380, using regular wave tests.

Experimental Wave Flume Tests in ROV-Wave Interaction Effects on the Line Tension for a Work Class ROV in Splash Zone

2021 ◽  
Author(s):  
Michael Binsar Lubis ◽  
Mehrdad Kimiaei
Keyword(s):  
Time History ◽  
Wave Interaction ◽  
Line Tension ◽  
Irregular Waves ◽  
Splash Zone ◽  
Remotely Operated Vehicle ◽  
Wave Flume ◽  
Flume Tests ◽  
Tension Time ◽  
Work Class

Abstract Integrity and stability of Remotely Operated Vehicle (ROV) when passing through the splash zone is one of the main concerns in the design of an ROV-umbilical system. Due to the lightweight nature of ROV in water, the umbilical experiences repetitive rapid transitions between slack and taut as the ROV travels through the splash zone. These rapid transitions induce tension spikes in the umbilical, namely snap forces, that can endanger the launch and recovery of an ROV. Therefore, it is important to ensure that the tension spikes do not exceed the safe working load of the umbilical. In this study, launch and recovery of a deep-water work class ROV are experimentally investigated using a 1:10 scaled ROV model through a series of wave flume tests. Different regular and irregular waves are generated in the flume while the ROV model is hung over the flume in four different positions. The tension time-history in the line is measured and recorded using a load cell at the top-end of the line. A simplified numerical model for launch and recovery of the ROV is developed and the numerical results are compared with the experimental ones. It is shown that the presented simplified model can be accurately used for analysis of launch and recovery of the ROV.

Determination of a Suitable Moment for Formwork Removal from a Concrete Structure Using Rebound Hammer Test Methods

2021 ◽  
Vol 322 ◽  
pp. 23-27
Author(s):  
Petr Misák ◽  
Dalibor Kocáb ◽  
Petr Cikrle
Keyword(s):  
Compressive Strength ◽  
Characteristic Curve ◽  
Test Methods ◽  
Rebound Hammer ◽  
Practical Applications ◽  
Relevant Topic ◽  
Compressive Strength Of Concrete ◽  
The Moment ◽  
Non Destructive

Determining the compressive strength of concrete in the early stages of ageing has been an increasingly relevant topic in recent years, particularly with regard to the safe removal of formwork from a structure or its part. The compressive strength of concrete which designates safe removal of formwork without damaging the structure can be referred to as "stripping strength". It is undoubtedly beneficial to be able to determine the moment of safe formwork removal in a non-destructive manner, i.e. without compromising the structure. Modern rebound hammer test methods seem to be a suitable instrument with which it is possible to reduce the length of technological breaks associated with concrete ageing to a minimum, and consequently, reduce the total cost of the construction. However, the use of these methods presents a number of challenges. As many conducted experiments have shown, there is no single conversion relationship (regression model) between non-destructive rebound hammer test methods and compressive strength. It is therefore advisable to always create a unique conversion relationship for each individual concrete. In addition, it must be noted that conventional regression analysis methods operate with 50% reliability. In construction testing, however, the most common is the so-called characteristic value, which is defined as a 5% quantile. This value is therefore determined with 95% reliability. This paper describes the construction of a so-called "characteristic curve", which can be used to estimate the compressive strength of concrete in a structure using rebound hammer test methods with 95% reliability. Consequently, the values obtained from the characteristic curve can be easily used for practical applications.

Investigation on Motion Responses of a Floating Wave Barrier in a Wave Flume Subjected to Regular Wave Action

2021 ◽  
pp. 281-288
Author(s):  
Hee Min Teh ◽  
Thinagran Silavaraj ◽  
Syed Shuja Ul Hassan ◽  
Eric Joseph Pereira
Keyword(s):  
Wave Action ◽  
Regular Wave ◽  
Wave Flume ◽  
Motion Responses
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