scholarly journals EXPERIMENTS ON BED FORM GENERATION BY WAVE ACTION

1972 ◽  
Vol 1 (13) ◽  
pp. 57 ◽  
Author(s):  
G.R. Mogridge ◽  
J.W. Kamphuis
Keyword(s):  
Specific Gravity ◽  
Wave Action ◽  
Water Tunnel ◽  
Oscillatory Flows ◽  
Wave Flume ◽  
Form Generation ◽  
Sediment Bed ◽  
Wide Range ◽  
Bed Forms ◽  
Bed Form

Experiments to determine the length, height and steepness of bed forms generated by wave action have been conducted in a laboratory wave flume and an oscillating water tunnel. The effects of a wide range of oscillatory flows were examined on polystyrene (specific gravity 1.05, diameter 1.54 mms), bakelite (specific gravity 1.60, diameter 0.52 mms), bakelite (specific gravity 1.51, diameter 0.67 mms) and sand (specific gravity 2.68, diameter 0.36 mms). From the results of the experiments design curves were plotted which make it possible to predict the length and height of bed form that will develop on any specified sediment bed for given conditions of fluid oscillation.

scholarly journals SCALE LAWS FOR BED FORMS IN LABORATORY WAVE MODELS

1974 ◽  
Vol 1 (14) ◽  
pp. 62
Author(s):  
G.R. Mogridge
Keyword(s):  
Experimental Study ◽  
Wave Action ◽  
Water Tunnel ◽  
Wave Flume ◽  
Wide Range ◽  
Bed Forms ◽  
Wave Models

An experimental study of the variables governing the development of bed forms under wave action has been conducted. A wide range of conditions was covered by the use of a wave flume and an oscillating water tunnel. Scale laws for modelling bed forms are developed using the results of these experiments. It is recommended that the model sediment used should be the same density as in the prototype and its size should be scaled geometrically. If this is not practical, it is shown how the scale laws can be used to minimise the distortion of the bed forms produced in the model.

Patterns in diversity and composition of the microbenthos of subarctic intertidal beaches with different morphodynamics

2020 ◽  
Vol 648 ◽  
pp. 19-38
Author(s):  
AI Azovsky ◽  
YA Mazei ◽  
MA Saburova ◽  
PV Sapozhnikov
Keyword(s):  
Species Abundance ◽  
Abundance Ratio ◽  
Wave Action ◽  
Coarse Grained ◽  
Sediment Properties ◽  
Β Diversity ◽  
Α Diversity ◽  
Wide Range ◽  
Similar Mode ◽  
Abundance And Diversity

Diversity and composition of benthic diatom algae and ciliates were studied at several beaches along the White and Barents seas: from highly exposed, reflective beaches with coarse-grained sands to sheltered, dissipative silty-sandy flats. For diatoms, the epipelic to epipsammic species abundance ratio was significantly correlated with the beach index and mean particle size, while neither α-diversity measures nor mean cell length were related to beach properties. In contrast, most of the characteristics of ciliate assemblages (diversity, total abundance and biomass, mean individual weight and percentage of karyorelictids) demonstrated a strong correlation to beach properties, remaining low at exposed beaches but increasing sharply in more sheltered conditions. β-diversity did not correlate with beach properties for either diatoms or ciliates. We suggest that wave action and sediment properties are the main drivers controlling the diversity and composition of the intertidal microbenthos. Diatoms and ciliates, however, demonstrated divergent response to these factors. Epipelic and epipsammic diatoms exhibited 2 different strategies to adapt to their environments and therefore were complementarily distributed along the environmental gradient and compensated for each other in diversity. Most ciliates demonstrated a similar mode of habitat selection but differed in their degree of tolerance. Euryporal (including mesoporal) species were relatively tolerant to wave action and therefore occurred under a wide range of beach conditions, though their abundance and diversity were highest in fine, relatively stable sediments on sheltered beaches, whereas the specific interstitial (i.e. genuine microporal) species were mostly restricted to only these habitats.

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 Design of a new hybrid artificial neural network method based on decision trees for calculating the Froude number in rigid rectangular channels

2016 ◽  
Vol 64 (3) ◽  
pp. 252-260 ◽  
Author(s):  
Isa Ebtehaj ◽  
Hossein Bonakdari ◽  
Amir Hossein Zaji ◽  
Charles Hin Joo Bong ◽  
Aminuddin Ab Ghani
Keyword(s):  
Decision Trees ◽  
Incipient Motion ◽  
Rigid Boundary ◽  
Sediment Bed ◽  
Economical Design ◽  
Rectangular Channels ◽  
Wide Range ◽  
Practical Engineering ◽  
Artificial Neural Network Method ◽  
Bed Thickness

Abstract A vital topic regarding the optimum and economical design of rigid boundary open channels such as sewers and drainage systems is determining the movement of sediment particles. In this study, the incipient motion of sediment is estimated using three datasets from literature, including a wide range of hydraulic parameters. Because existing equations do not consider the effect of sediment bed thickness on incipient motion estimation, this parameter is applied in this study along with the multilayer perceptron (MLP), a hybrid method based on decision trees (DT) (MLP-DT), to estimate incipient motion. According to a comparison with the observed experimental outcome, the proposed method performs well (MARE = 0.048, RMSE = 0.134, SI = 0.06, BIAS = -0.036). The performance of MLP and MLP-DT is compared with that of existing regression-based equations, and significantly higher performance over existing models is observed. Finally, an explicit expression for practical engineering is also provided.

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

scholarly journals WAVE FORCES ON SQUARE CAISSONS

1976 ◽  
Vol 1 (15) ◽  
pp. 132 ◽  
Author(s):  
G.R. Mogridge ◽  
W.W. Jamieson
Keyword(s):  
Experimental Data ◽  
Theoretical Method ◽  
Wave Forces ◽  
Simple Method ◽  
Method Of Calculation ◽  
Wave Flume ◽  
Wide Range ◽  
Wave Heights ◽  
And Storage ◽  
Water Depths

The forces and overturning moments exerted by waves on large vertical square-section caissons have been measured in the laboratory. Each model caisson extended from the bottom of a wave flume through the water surface and was oriented either with one side perpendicular to the direction of wave propagation or turned through an angle of forty-five degrees to this position. For a given orientation, each model was tested for a range of wave heights (up to the point of breaking) for various wave periods and water depths. A digital computer was used for the acquisition, processing, plotting and storage of the experimental data. In addition to the experimental work, an approximate theoretical method is presented which allows the wave loadings on a square caisson to be estimated by means of a simple desk calculation. The experimental data shows that this simple method of calculation is reasonably accurate over a wide range of wave conditions and caisson sizes.

scholarly journals A further note upon "inter-traction."

1926 ◽  
Vol 112 (760) ◽  
pp. 213-214
Keyword(s):  
Specific Gravity ◽  
Interfacial Tension ◽  
Simple Technique ◽  
Cell Compartments ◽  
Previous Communication ◽  
Wide Range ◽  
And Diffusion ◽  
Adjoining Cell

I pointed out in a previous communication that a mixture of fluids can be brought about not only by the operations of mechanical convection and diffusion, but also by the impulsion of a force which can very rapidly carry down a lighter overlying fluid into a heavier underlying fluid in the form of characteristic pseudopodial streamers, conveying at the same time the heavier underlying fluid into the lighter superjacent fluid in the form of a palisade of ascending streams. I have ventured to call the agency by which this reciprocal instreaming is produced:― inter-traction . These phenomena which I described as occuring when salt, and also sugar, solutions brought into contract with albuminous solutionscan, as Schoneboom showed, be obtained also with a very wide range of substances; and they have been ascribed by him to the operations of negative interfacial tension, and identified with phenomena theoretically anticipated by Clerk-Maxwell. Adam and Jessop, in a further communication, have insisted that the pseudopodial streaming is attributable to operations of diffusion and resulting changes in specific gravity, and they have stressed the point that the characteristic appearances can be obtained only when the lighter is superposed upon the heavier fluid, and not when the fluids are disposed side by side. In view of the fact that the conclusion that horizontal streaming cannot be obtained rests only upon experiments conducted by filling fluids of different specific gravity into adjoining cell compartments, and then removing the dividing wall, it seemed desirable to try for horizantal inter-traction with a technique which would get rid of the complication of the heavier fluid sinking to the bottom and the lighter going to the top of the vessel, and would allow of more accurate and deliberate observation. The quite simple technique now to be described satisfies these desiderata.

The role of surface cohesion is wind-driven snow transport

2020 ◽  
Author(s):  
Francesco Comola ◽  
Johan Gaume ◽  
Jasper Kok ◽  
Michael Lehning
Keyword(s):  
Blowing Snow ◽  
Snow Surface ◽  
Wind Speeds ◽  
Wide Range ◽  
Bed Forms ◽  
Geophysical Processes ◽  
Order Of Magnitude ◽  
History Of ◽  
Snow Transport

<p>The wind-driven saltation of sediments, such as snow and sand, is responsible for a wide range of geophysical processes. Blowing-snow, in particular, affects snow surface properties and drives snow redistribution in alpine terrain. As such, it is of fundamental importance for avalanche mechanics. One of the most important controls on initiation and development of snow saltation is the surface cohesion induced by ice particle sintering. Although inter-particle cohesion is known to limit the number of grains lifted from the surface through aerodynamic entrainment and granular splash, the role of cohesion in the development of saltation from onset to steady state is still poorly understood. Using a numerical model based on the discrete element method, we show that saltation over cohesive beds sustains itself at wind speeds one order of magnitude smaller than those necessary to initiate it, giving rise to hysteresis in which the occurrence of transport depends on the history of the wind. Our results further suggest that saltation over cohesive beds requires much longer distances to saturate, thereby increasing the size of the smallest stable bed forms.</p>

Propeller Cavitation Breakdown Analysis

2005 ◽  
Vol 127 (5) ◽  
pp. 995-1002 ◽  
Author(s):  
Jules W. Lindau ◽  
David A. Boger ◽  
Richard B. Medvitz ◽  
Robert F. Kunz
Keyword(s):  
Multiphase Flow ◽  
Computational Model ◽  
Navier Stokes ◽  
Water Tunnel ◽  
Computational Results ◽  
Cavity Size ◽  
Size And Shape ◽  
Wide Range ◽  
Reynolds Averaged Navier Stokes ◽  
Thrust And Torque

A Reynolds-averaged Navier-Stokes computational model of homogeneous multiphase flow is presented. Cavitation driven thrust and torque breakdown over a wide range of advance ratios is modeled for an open propeller. Computational results are presented as a form of validation against water tunnel measured thrust and torque breakdown for the propeller. Successful validation of the computational model is achieved. Additional observations are made with regards to cavity size and shape as well as cavitation breakdown behavior.

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