scholarly journals RANDOM BREAKING WAVES HORIZONTAL SEABED

1986 ◽  
Vol 1 (20) ◽  
pp. 68 ◽  
Author(s):  
Hans Peter Riedel ◽  
Anthony Paul Byrne
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Breaking Waves ◽  
Random Wave ◽  
Random Waves ◽  
Flume Experiments ◽  
Depth Ratio ◽  
Wave Trains ◽  
Monochromatic Waves

According to wave theories the depth limited wave height over a horizontal seabed has a wave height to water depth ratio (H/d) of about 0.8. Flume experiments with monochromatic waves over a horizontal seabed have failed to produce H/d ratios greater than 0.55. However designers still tend to use H/d 0.8 for their design waves. Experiments have been carried out using random wave trains in the flume over a horizontal seabed. These experiments have shown that the limiting H/d ratio of 0.55 applies equally well to random waves.

Bulk drag coefficient of a subaquatic vegetation subjected to irregular waves: Influence of Reynolds and Keulegan-Carpenter numbers

2020 ◽  
pp. 34-42
Author(s):  
Thibault Chastel ◽  
Kevin Botten ◽  
Nathalie Durand ◽  
Nicole Goutal
Keyword(s):  
Drag Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Empirical Relationship ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Geometrical Parameters ◽  
Flume Experiments ◽  
Seagrass Meadows ◽  
Artificial Vegetation

Seagrass meadows are essential for protection of coastal erosion by damping wave and stabilizing the seabed. Seagrass are considered as a source of water resistance which modifies strongly the wave dynamics. As a part of EDF R & D seagrass restoration project in the Berre lagoon, we quantify the wave attenuation due to artificial vegetation distributed in a flume. Experiments have been conducted at Saint-Venant Hydraulics Laboratory wave flume (Chatou, France). We measure the wave damping with 13 resistive waves gauges along a distance L = 22.5 m for the “low” density and L = 12.15 m for the “high” density of vegetation mimics. A JONSWAP spectrum is used for the generation of irregular waves with significant wave height Hs ranging from 0.10 to 0.23 m and peak period Tp ranging from 1 to 3 s. Artificial vegetation is a model of Posidonia oceanica seagrass species represented by slightly flexible polypropylene shoots with 8 artificial leaves of 0.28 and 0.16 m height. Different hydrodynamics conditions (Hs, Tp, water depth hw) and geometrical parameters (submergence ratio α, shoot density N) have been tested to see their influence on wave attenuation. For a high submergence ratio (typically 0.7), the wave attenuation can reach 67% of the incident wave height whereas for a low submergence ratio (< 0.2) the wave attenuation is negligible. From each experiment, a bulk drag coefficient has been extracted following the energy dissipation model for irregular non-breaking waves developed by Mendez and Losada (2004). This model, based on the assumption that the energy loss over the species meadow is essentially due to the drag force, takes into account both wave and vegetation parameter. Finally, we found an empirical relationship for Cd depending on 2 dimensionless parameters: the Reynolds and Keulegan-Carpenter numbers. These relationships are compared with other similar studies.

scholarly journals STATISTICAL PROPERTIES OF RANDOM WAVE GROUPS

1980 ◽  
Vol 1 (17) ◽  
pp. 175 ◽  
Author(s):  
Akira Kimura
Keyword(s):  
Wave Height ◽  
Transition Probabilities ◽  
Probability Distributions ◽  
Group Formation ◽  
Rayleigh Distribution ◽  
Statistical Properties ◽  
Wave Period ◽  
Random Wave ◽  
Random Waves ◽  
Resonant Wave

This study deals with the statistical properties of the group formation of random waves determined by the zero-up-cross method. Probability distributions about (1) the run of high waves (2) the total run (3) the run of resonant wave period are derived theoretically providing that the time series of wave height and wave period form the Markov chain. Transition probabilities are given by the 2-dimensional Rayleigh distribution for the wave height train and the 2-dimensional Weibull distribution for the wave period train. And very good agreements between data and the theoretical distributions have been obtained. Then the paper discusses those parameters which affect the statistical properties of the runs and shows that the spectrum peakedness parameter for the. run of wave height and the spectrum width parameter for the run of wave period are the most predominant.

scholarly journals ENERGY LOSS AND SET-UP DUE TO BREAKING OF RANDOM WAVES

1978 ◽  
Vol 1 (16) ◽  
pp. 32 ◽  
Author(s):  
J.A. Battjes ◽  
J.P.F.M. Janssen
Keyword(s):  
Wave Height ◽  
Dissipation Rate ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Height Distribution ◽  
Random Waves ◽  
Dissipation Of Energy ◽  
Wave Height Distribution ◽  
Set Up ◽  
Local Depth

A description is given of a model developed for the prediction of the dissipation of energy in random waves breaking on a beach. The dissipation rate per breaking wave is estimated from that in a bore of corresponding height, while the probability of occurrence of breaking waves is estimated on the basis of a wave height distribution with an upper cut-off which in shallow water is determined mainly by the local depth. A comparison with measurements of wave height decay and set-up, on a plane beach and on a beach with a bar-trough profile, indicates that the model is capable of predicting qualitatively and quantitatively all the main features of the data.

Research and Analysis on the Wave Transformation and Irregular Wave Breaking Criterion on the Shore

2016 ◽  
Vol 858 ◽  
pp. 354-358
Author(s):  
Tao You ◽  
Li Ping Zhao ◽  
Zheng Xiao ◽  
Lun Chao Huang ◽  
Xiao Rui Han
Keyword(s):  
Theoretical Model ◽  
Wave Height ◽  
Wave Breaking ◽  
Surf Zone ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Breaking Wave ◽  
Height Distribution ◽  
Flume Experiments ◽  
Irregular Wave

Within the surf zone which is the region extending from the seaward boundary of wave breaking to the limit of wave uprush, breaking waves are the dominant hydrodynamics acting as the key role for sediment transport and beach profile change. Breaking waves exhibit various patterns, principally depending on the incident wave steepness and the beach slope. Based on the equations of conservation of mass, momentum and energy, a theoretical model for wave transformation in and outside the surf zone was obtained, which is used to calculate the wave shoaling, wave set-up and set down and wave height distributions in and outside the surf zone. The analysis and comparison were made about the breaking point location and the wave height variation caused by the wave breaking and the bottom friction, and about the wave breaking criterion under regular and irregular breaking waves. Flume experiments relating to the regular and irregular breaking wave height distribution across the surf zone were conducted to verify the theoretical model. The agreement is good between the theoretical and experimental results.

scholarly journals DEFORMATION UP TO BREAKING OF PERIODIC WAVES ON A BEACH

1976 ◽  
Vol 1 (15) ◽  
pp. 26 ◽  
Author(s):  
Ib A. Svendson ◽  
J. Buhr Hansen
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Wave Length ◽  
Empirical Relation ◽  
Breaking Point ◽  
Periodic Waves ◽  
Depth Ratio ◽  
Surface Profiles ◽  
Deep Water Wave ◽  
Sloping Beach

An experimental description is presented for 'the transformation of periodic waves which approach breaking on a gently sloping beach. The data include the variation of wave height, phase velocity, wave surface profiles, and the maximum value of the wave height to water depth ratio (H/h)max around the breaking point. The results are compared with the theories of sinusoidal and cnoidal wave shoaling, and the latter is shown in most cases to agree remarkably well when the laminar energy loss along the walls and bottom of the wave tank is included. An empirical relation is established between wave length to water depth ratio L/h at the breaking point and the deep water wave steepness H0/L0. Also the maximum wave height to water depth ratio at breaking shows considerably less scattering than found previously, when plotted versus S = hx L/h, hx being bottom slope.

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 STABILITY OF RUBBLE MOUND BREAKWATER

1980 ◽  
Vol 1 (17) ◽  
pp. 120 ◽  
Author(s):  
J. Feuillet ◽  
M. Sabaton
Keyword(s):  
Wave Height ◽  
Breaking Waves ◽  
Random Waves ◽  
Regular Waves ◽  
T Wave ◽  
Design Wave Height ◽  
Storm Duration ◽  
Equivalent Wave ◽  
Rubble Mound ◽  
The Stability

The stability of a rubble mound breakwater section, with 3 in 2 armour slope, was tested under random waves attack. Tests analysis shows that the equivalent wave height characterizing the spectrum to be used in a stability formula elaborated with regular waves (for instance the Hudson's formula) is the upper twentieth height of the distribution for a storm duration of 6 hours. An analytical expression of the damage evolution as function of time modulates this choice according to the storm duration. The same rubble mound breakwater was also tested under the action of regular breaking waves. The damage was expressed in terms of the four following parameters : H0 : wave height T : wave period Dp : water depth at the toe of the structure Djj : breaker depth without the breakwater For a given wave height, the most important damage occur when : °b In this case the design wave height must be increased by about 30 % when using a stability formula elaborated for non breaking waves.

Numerical Investigation of Deepwater S-Lay Pipeline Under Freak Waves

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Pu Xu ◽  
Shunfeng Gong
Keyword(s):  
Structure Design ◽  
Dynamic Responses ◽  
Random Wave ◽  
Superposition Method ◽  
Random Waves ◽  
Transient Wave ◽  
Freak Waves ◽  
Freak Wave ◽  
Offshore Pipeline ◽  
Wave Trains

Abstract Freak wave is an extreme sea state with unexpected and huge wave height, which becomes a potential risk for lay barge and offshore pipeline during deepwater installation. In order to investigate the dynamic responses of deepwater S-lay pipeline induced by freak waves, this study developed a comprehensive numerical model with the particular consideration of the freak wave effect. An enhanced superposition method of combined transient wave trains and random wave trains was presented, and a series of freak wave trains were generated. The induced pipelay vessel motions were simulated by the use of displacement response amplitude operators (RAOs). The pipe–stinger roller interactions in the overbend and the cyclic contacts between the pipeline and seabed soil in the touchdown zone (TDZ) were fully taken into consideration. The developed S-lay model was subsequently utilized to calculate the dynamic responses of the pipelay vessel and offshore pipeline under random waves and freak waves for a comparison. The results illustrated the remarkable influence of freak waves on the systematic behaviors of deepwater S-laying pipeline, which offer a significant theoretical basis for the pipe structure design and pipelay operation safety.

scholarly journals Detection of Plunging Breaking Waves Based on Machine Learning

2018 ◽  
Author(s):  
Ying Tu ◽  
Zhengshun Cheng ◽  
Michael Muskulus
Keyword(s):  
Machine Learning ◽  
Wave Height ◽  
Water Depth ◽  
Experimental Studies ◽  
Classification Problem ◽  
Breaking Waves ◽  
Offshore Structures ◽  
Trained Classifier ◽  
Structural Loading ◽  
Logistic Regression Algorithm

Plunging breaking waves that occur in the vicinity of offshore structures can lead to high impulsive slamming loads, which are significant for the structural loading. The occurrence of plunging breaking waves is usually identified based on criteria that are derived from theoretical analyses and experimental studies. Given a large amount of data, detecting plunging breaking waves can be treated as a typical classification problem, which can be solved by a machine learning approach. In this study, logistic regression algorithm is used together with the experimental data from the WaveSlam project to train a classifier for the detection. Three normalized dimensionless features are introduced based on the measured data for the training. A classifier with respect to four wave parameters (i.e. water depth, wave height, crest height and wave period) is then explicitly developed for detecting plunging breaking waves. It is found that the trained classifier has an accuracy of 98.7% and F1 score of 99.2% for the tested data. Among the three dimensionless parameters, the ratio of wave height to water depth, H/d, is the most decisive factor for the detection of plunging breaking waves.

Calibration of a 58 m wave flume

1981 ◽  
Vol 8 (4) ◽  
pp. 449-455 ◽  
Author(s):  
D. B. Muggeridge ◽  
J. J. Murray
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Random Wave ◽  
Regular Waves ◽  
M Wave ◽  
Wave Flume ◽  
Wind Speeds ◽  
On Line ◽  
Predicted Values ◽  
Good Agreement

A 58.27 × 4.57 × 3.04 m wave flume has been constructed and calibrated. The maximum wave height that can be generated in regular waves is 0.7 m at a water depth of 1.8 m. Random wave spectra have also been modelled in the flume for prototype wind speeds up to 25 m/s. The maximum significant wave height that can be generated at a 1 m water depth is 20 cm.A series of tests performed to verify design curves presented by Gilbert, Thompson, and Brewer show good agreement with the predicted values. The Pierson-Moskowitz spectrum was modelled between wind speeds of 5 and 25 m/s at suitable scale factors ranging from 1:50 to 1:150. All analysis was carried out in real time by means of an on-line computer.

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