scholarly journals A MODEL FOR OFFSHORE SEDIMENT TRANSPORT

1984 ◽  
Vol 1 (19) ◽  
pp. 97 ◽  
Author(s):  
M.J.F. Stive ◽  
J.A. Battjes
Keyword(s):  
Sediment Transport ◽  
Equilibrium State ◽  
Return Flow ◽  
Random Wave ◽  
Two Dimensional ◽  
Random Waves ◽  
Water Motion ◽  
First Approximation

Observation of the two-dimensional breaking of random waves on a beach suggests that under conditions of active surf an important mechanism in the process of offshore sediment transport is the transport by the undertow or return flow, induced by the breaking of waves. It is found that a model incorporating this mechanism exclusively is able to describe the local sediment transport and the resulting bottom variation of a beach under random wave attack to a first approximation. A laboratory verification is made based on measurements of both the dynamics of the water motion and the bottom profile. Finally, a realistic equilibrium state is shown to result from the model

scholarly journals Method of the Laboratory Wave Generation for Two Dimensional Hydraulic Model Experiment in the Coastal Engineering Fields: Case of Random Waves

2021 ◽  
Vol 33 (6) ◽  
pp. 383-390
Author(s):  
Jong-In Lee ◽  
Il Rho Bae ◽  
Young-Taek Kim
Keyword(s):  
Wave Generation ◽  
Hydraulic Model ◽  
Coastal Engineering ◽  
Experimental Results ◽  
Random Wave ◽  
Two Dimensional ◽  
Random Waves ◽  
Coastal Structures ◽  
Successful Execution ◽  
The Stability

The experiments in coastal engineering are very complex and a lot of components should be concerned. The experience has an important role in the successful execution. Hydraulic model experiments have been improved with the development of the wave generator and the advanced measuring apparatus. The hydraulic experiments have the advantage, that is, the stability of coastal structures and the hydraulic characteristics could be observed more intuitively rather than the numerical modelings. However, different experimental results can be drawn depending on the model scale, facilities, apparatus, and experimenters. In this study, two-dimensional hydraulic experiments were performed to suggest the guide of the test wave(random wave) generation, which is the most basic and important factor for the model test. The techniques for generating the random waves with frequency energy spectrum and the range for the incident wave height [(HS)M/(HS)T = 1~1.05] were suggested. The proposed guide for the test wave generation will contribute to enhancing the reliability of the experimental results in coastal engineering.

scholarly journals SCOUR ABOUT A SINGLE, CYLINDRICAL PILE DUE TO COMBINED RANDOM WAVES AND A CURRENT

1986 ◽  
Vol 1 (20) ◽  
pp. 136 ◽  
Author(s):  
Robert W. Eadie ◽  
John B. Herbich
Keyword(s):  
Random Wave ◽  
Two Dimensional ◽  
Random Waves ◽  
Sediment Size ◽  
Waves And Currents ◽  
Using Data ◽  
Almost All ◽  
A Current ◽  
Water Depths ◽  
Monochromatic Waves

There have been many studies of scour around piles caused by waves, and some studies of scour by waves and currents combined. However, almost all of the studies were conducted with monochromatic waves. The purpose of this investigation was to study what scouring effects various currents and random waves have on a single, cylindrical pile. These results were then compared with the results from previous studies of scour resulting from currents and monochromatic waves at Texas A&M University (Armbrust, 1982 and Wang, 1983). Experiments were conducted in a two-dimensional wave tank. The pile used in this study had a diameter of 1.5 inches. Two water depths, four currents, one sediment size and four random wave spectra were utilized. Using data obtained from the experiments, an attempt was made to describe scour in terms of relevant dimensionless parameters.

scholarly journals SEDIMENT TRANSPORT ON NEARLY-PRISMATIC BEACHES

1988 ◽  
Vol 1 (21) ◽  
pp. 128
Author(s):  
Marcel J.F. Stive ◽  
J.A. Roelvink
Keyword(s):  
Sediment Transport ◽  
Recent Progress ◽  
Dynamic Modelling ◽  
Two Dimensional ◽  
Random Waves ◽  
Beach Profile ◽  
Quantitative Modelling ◽  
Obliquely Incident ◽  
Current Systems ◽  
Profile Development

Recent progress in the quantitative modelling of the undertow has stimulated the modelling of cross-shore sediment transport. More so than before it seems now possible to attempt the dynamic modelling of beach profile development. Also, integration of dynamic cross-shore sediment transport formulations in horizontally two-dimensional models for watermotion and sediment transport has recently been suggested. This seems to be a first step of integrating depth-averaged 2DH-modelling with 2DV-profile- modelling. Here an overview is given of these developments and the understanding gained sofar of the several current systems and the induced sediment transport and morphology that are found in the situation of random waves normally and obliquely incident on beaches which vary not or only slowly alongshore.

scholarly journals Time Scale for Scour Beneath Pipelines Due to Long-Crested and Short-Crested Nonlinear Random Waves Plus Current

2021 ◽  
Vol 9 (2) ◽  
pp. 114
Author(s):  
Dag Myrhaug ◽  
Muk Chen Ong
Keyword(s):  
Time Scale ◽  
Current Flow ◽  
Irregular Waves ◽  
Wave Crest ◽  
Random Wave ◽  
Random Waves ◽  
Flow Conditions ◽  
Regular Waves ◽  
Nonlinear Random Waves ◽  
2D And 3D

This article derives the time scale of pipeline scour caused by 2D (long-crested) and 3D (short-crested) nonlinear irregular waves and current for wave-dominant flow. The motivation is to provide a simple engineering tool suitable to use when assessing the time scale of equilibrium pipeline scour for these flow conditions. The method assumes the random wave process to be stationary and narrow banded adopting a distribution of the wave crest height representing 2D and 3D nonlinear irregular waves and a time scale formula for regular waves plus current. The presented results cover a range of random waves plus current flow conditions for which the method is valid. Results for typical field conditions are also presented. A possible application of the outcome of this study is that, e.g., consulting engineers can use it as part of assessing the on-bottom stability of seabed pipelines.

scholarly journals The two-dimensional hydrodynamical theory of moving aerofoils. IV

1947 ◽  
Vol 188 (1015) ◽  
pp. 439-463
Keyword(s):  
Stability Problem ◽  
Two Dimensional ◽  
Centre Of Gravity ◽  
First Approximation ◽  
Von Karman ◽  
Moving Cylinder ◽  
Period Equation ◽  
The Stability ◽  
Von Kármán ◽  
Hydrodynamical Theory

In the first part of this paper opportunity has been taken to make some adjustments in certain general formulae of previous papers, the necessity for which appeared in discussions with other workers on this subject. The general results thus amended are then applied to a general discussion of the stability problem including the effect of the trailing wake which was deliberately excluded in the previous paper. The general conclusion is that to a first approximation the wake, as usually assumed, has little or no effect on the reality of the roots of the period equation, but that it may introduce instability of the oscillations, if the centre of gravity of the element is not sufficiently far forward. During the discussion contact is made with certain partial results recently obtained by von Karman and Sears, which are shown to be particular cases of the general formulae. An Appendix is also added containing certain results on the motion of a vortex behind a moving cylinder, which were obtained to justify certain of the assumptions underlying the trail theory.

scholarly journals Effects of Diurnal Variations on Tropical Equilibrium States: A Two-Dimensional Cloud-Resolving Modeling Study

2007 ◽  
Vol 64 (2) ◽  
pp. 656-664 ◽  
Author(s):  
Shouting Gao ◽  
Yushu Zhou ◽  
Xiaofan Li
Keyword(s):  
Equilibrium State ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Diurnal Variations ◽  
Equilibrium States ◽  
Sea Surface ◽  
Two Dimensional ◽  
Time Invariant

Abstract Effects of diurnal variations on tropical heat and water vapor equilibrium states are investigated based on hourly data from two-dimensional cloud-resolving simulations. The model is integrated for 40 days and the simulations reach equilibrium states in all experiments. The simulation with a time-invariant solar zenith angle produces a colder and drier equilibrium state than does the simulation with a diurnally varied solar zenith angle. The simulation with a diurnally varied sea surface temperature generates a colder equilibrium state than does the simulation with a time-invariant sea surface temperature. Mass-weighted mean temperature and precipitable water budgets are analyzed to explain the thermodynamic differences. The simulation with the time-invariant solar zenith angle produces less solar heating, more condensation, and consumes more moisture than the simulation with the diurnally varied solar zenith angle. The simulation with the diurnally varied sea surface temperature produces a colder temperature through less latent heating and more IR cooling than the simulation with the time-invariant sea surface temperature.

scholarly journals Two-dimensional numerical modeling of chemical transport–transformation in fluvial rivers: formulation of equations and physical interpretation

2009 ◽  
Vol 11 (2) ◽  
pp. 106-118 ◽  
Author(s):  
Sui Liang Huang
Keyword(s):  
Sediment Transport ◽  
Chemical Transport ◽  
Transformation Model ◽  
Diffusion Equations ◽  
Desorption Kinetics ◽  
Two Dimensional ◽  
Transformation Equation ◽  
Governing Equations ◽  
Convection Diffusion ◽  
Kinetics Of

Based on previous work on the transport–transformation model of heavy metal pollutants in fluvial rivers, this paper presents the formulation of a two-dimensional model to describe chemical transport–transformation in fluvial rivers by considering basic principles of environmental chemistry, hydraulics and mechanics of sediment transport and recent developments along with three very simplified test cases. The model consists of water flow governing equations, sediment transport governing equations, transport–transformation equation of chemicals and convection–diffusion equations of sorption–desorption kinetics of particulate chemical concentrations on suspended load, bed load and bed sediment. The chemical transport–transformation equation is basically a mass balance equation. It demonstrates how sediment transport affects transport–transformation of chemicals in fluvial rivers. The convection–diffusion equations of sorption–desorption kinetics of chemicals, being an extension of batch reactor experimental results, take both physical transport, i.e. convection and diffusion, and chemical reactions, i.e. sorption–desorption into account. The effects of sediment transport on chemical transport–transformation were clarified through three simple examples. Specifically, the transport–transformation of chemicals in a steady, uniform and equilibrium sediment-laden flow was calculated by applying this model, and results were shown to be rational. Both theoretical analysis and numerical simulation indicated that the transport–transformation of chemicals in sediment-laden flows with a clay-enriched riverbed possesses not only the generality of common tracer pollutants, but also characteristics of transport–transformation induced by sediment motion. Future work will be conducted to present the validation/application of the model with available data.

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