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.

A study of the stability of dynamically stable breakwaters

1991 ◽  
Vol 18 (6) ◽  
pp. 916-925 ◽  
Author(s):  
K. R. Hall ◽  
Joseph S. Kao
Keyword(s):  
Research Laboratory ◽  
Coastal Engineering ◽  
Irregular Waves ◽  
Two Dimensional ◽  
Uniformity Coefficient ◽  
Engineering Research ◽  
Hydraulic Models ◽  
Wave Flume ◽  
The Stability ◽  
Dimensional Wave

The effect of gradation of armour stones and the amount of rounded stones in the armour on dynamically stable breakwaters was assessed in a two-dimensional wave flume. A total of 52 series of tests were undertaken at the Coastal Engineering Research Laboratory of Queen's University, Kingston, Canada using irregular waves. Profiles of the structure during the various stages of reshaping were measured using a semiautomatic profiler developed for this study. Four gradations of armour stones were used, giving a range in uniformity coefficient of 1.35–5.4. The volume of stones and the initial berm width required for the development of a stable profile, along with the extent to which the toe of the structure progressed seaward, were chosen as representative parameters of the reshaped breakwater. The results indicated that the toe width formed as a result of reshaping and the area of stones required for reshaping were dependent on the gradation of the armour stones. The initial berm width required for reshaping was also found to be dependent on the gradation and the percentage of rounded stones in the armour. Key words: breakwaters, dynamic stability, hydraulic models, stability, armour stones.

scholarly journals Reflection Analysis of Impermeable Slopes under Bimodal Sea Conditions

2020 ◽  
Author(s):  
Stephen Orimoloye ◽  
Harshinie Karunarathna ◽  
Dominic Reeve
Keyword(s):  
Reflection Coefficient ◽  
Wave Reflection ◽  
Experimental Tests ◽  
Random Wave ◽  
Random Waves ◽  
Coastal Structures ◽  
Test Analysis ◽  
Relative Water ◽  
Analysis Of Results ◽  
Reflection Characteristics

Understanding of reflection characteristics of coastal seawalls is crucial for design. Wave reflection can cause difficulties to small vessel manoeuvring at the harbour entrance and constitute damaging scouring at the toe of coastal structures. Previous studies have considered reflection characteristics of coastal seawalls under wind-generated random waves without paying attention to the effects of wave bimodality created by the presence of swell waves. The present study focuses on the influence of random wave bimodality on reflective characteristics of coastal seawalls. More than eight hundred experimental tests have been conducted to examine the reflection performance of impermeable sloping seawalls under bimodal waves. Reflection coefficients were computed from each test. Analysis of results suggests that both unimodal and bimodal waves give similar reflection characteristics. However, the reflection coefficient in bimodal sea states seems to be more prolonged than in the unimodal sea states. It was found that the reflection coefficient of coastal seawalls is strongly influenced by the seawall slope, the wave steepness, relative water depth, and the surf similarity parameters. A new empirical reflection equation to describe the influence of wave bimodality on the reflection characteristics of coastal seawalls has been formulated based on this study.

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 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 3-D HYDRAULIC MODEL OF WAVES GENERATED BY DISPLACEMENTS

1976 ◽  
Vol 1 (15) ◽  
pp. 62
Author(s):  
Shin-Lin Liu ◽  
R.L. Wiegel
Keyword(s):  
Water Level ◽  
Froude Number ◽  
Water Depth ◽  
Water Waves ◽  
Model Experiment ◽  
Three Dimensional ◽  
Hydraulic Model ◽  
Experimental Results ◽  
Horizontal Motion ◽  
Two Dimensional

Measurements were made of the water waves generated by the horizontal motion of submerged plungers. The results obtained in a three-dimensional hydraulic model experiment, using a plunger 0.5 ft. wide and 0.25 ft. high, were compared with both the experimental results and theory for the two dimensional case. It was found that at a given location the ratio of the elevation above the still water level (SWL) of the first wave (the largest wave of the group for the range of variables tested) to the displacement of the plunger (HgA) was found to be dependent upon the Froude Number Npa (based upon the average plunger speed and the water depth) and upon the ratio of the height of the plunger to the water depth (D/d). For a constant value of 9, H3/A increased with increasing Npav„ and D/d. A few additional tests were made using a plunger 2.0 ft. wide and 0.25 ft. high. The results show that Ho/A depends also upon the ratio of water depth to the width of the plunger (d/W).

scholarly journals The effect of surface tension on the shape of fingers in a Hele Shaw cell

1981 ◽  
Vol 102 ◽  
pp. 455-469 ◽  
Author(s):  
J. W. McLean ◽  
P. G. Saffman
Keyword(s):  
Surface Tension ◽  
Experimental Results ◽  
Two Dimensional ◽  
Singular Perturbation Analysis ◽  
Linearized Stability ◽  
Finger Width ◽  
The Stability ◽  
Hele Shaw Cell ◽  
Effect Of Surface ◽  
Small Disturbances

The experimental results of Saffman & Taylor (1958) and Pitts (1980) on fingering in a Hele Shaw cell are modelled by two-dimensional potential flow with surface-tension effects included at the interface. Using free streamline techniques, the shape of the free surface is expressed as the solution of a nonlinear integro-differential equation. The equation is solved numerically and the solutions are compared with experimental results. The shapes of the profiles are very well predicted, but the dependence of finger width on surface tension is not quantitatively accurate, although the qualitative behaviour is correct. A conflict between the numerics and a formal singular perturbation analysis is noted but not resolved. The stability of the steady finger to small disturbances is also examined. Linearized stability analysis indicates that the two-dimensional fingers are not stabilized by the surface-tension effect, which disagrees with the experimental observations. A possible reason for the discrepancy between theory and experiment is suggested.

scholarly journals RANDOM WAVE SIMULATION IN A LABORATORY WAVE TANK

1976 ◽  
Vol 1 (15) ◽  
pp. 20 ◽  
Author(s):  
Akira Kimura ◽  
Yuichi Iwagaki
Keyword(s):  
Simulation System ◽  
Random Wave ◽  
New Wave ◽  
Random Waves ◽  
Sea Waves ◽  
Coastal Structures ◽  
Wave Tank ◽  
Wave Simulation ◽  
Simulation Techniques ◽  
Engineering Problems

Most of coastal engineering problems have been studied with monocromatic waves. However, sea waves which arrive at the coast are random. It is very difficult to estimate exactly the influence of these random waves to coastal structures. Then the model tests in a laboratory wave tank using random wave simulation techniques seem to be most desirable way to estimate the influence of randomness of sea waves. For this purpose, the accomplishment of random wave simulation system, which make possible generating random waves having statistically same properties as those of sea waves, has long been desired. The authors achieved to establish such a new wave simulation system. In this paper, the characteristics of this system are demonstrated experimentally through several cases of random wave simulations.

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.

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