scholarly journals THE DYNAMIC RESPONSE OF SHINGLE BEACHES TO RANDOM WAVES

1988 ◽  
Vol 1 (21) ◽  
pp. 130 ◽  
Author(s):  
K.A. Powell
Keyword(s):  
Field Data ◽  
Wave Reflection ◽  
Relative Magnitude ◽  
Random Wave ◽  
Random Waves ◽  
Wave Flume ◽  
Probabilistic Distribution ◽  
Laboratory Results ◽  
Run Up ◽  
Reflection Characteristics

An extensive laboratory investigation into the behaviour of shingle beaches has been undertaken using a large random wave flume. The study utilised a lightweight material scaled to reproduce the correct permeability of the beach, and the correct threshold and relative magnitude of the onshore/offshore movement. Results are presented describing both the wave reflection characteristics of the beach and the probabilistic distribution of wave run-up crests on the foreshore. Where possible the laboratory results are validated against field data.

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.

Experimental Studies of Surface Wave Reflection by Longshore Bars and a Sloping Seawall

2002 ◽  
Author(s):  
P. Dong ◽  
Y. Wang
Keyword(s):  
Laboratory Experiments ◽  
Wave Reflection ◽  
Experimental Studies ◽  
Considerable Influence ◽  
Wave Surface ◽  
Regular Waves ◽  
Wave Flume ◽  
The Waves ◽  
Resonant Reflection ◽  
Reflection Characteristics

Laboratory experiments have been performed to investigate the effects of a seawall on resonant reflection by a fixed periodic bar system on the seabed. The experiments were conducted in a wave flume. A series of five fixed bars was placed in front of a seawall with 1:1 slope. Regular waves with wave height 0.04m and wave periods from 0.8 to 1.20 seconds were used. The tests were performed for the cases with and without the seawall. The wave surface elevations were measured at seven locations in front of the seaward and in either side the bar patch. Based on the preliminary analysis of measured wave time series, it was found that the presence of the seawall has considerable influence on the reflection characteristics of the waves in front of the bar field.

Reconstruction and Analysis of Freak Waves Generated From Unidirectional Random Waves

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Yuxiang Ma ◽  
Changfu Yuan ◽  
Congfang Ai ◽  
Guohai Dong
Keyword(s):  
Time Series ◽  
Extreme Event ◽  
Wave Model ◽  
Rogue Waves ◽  
Random Wave ◽  
Random Waves ◽  
Long Distance ◽  
Freak Waves ◽  
Freak Wave ◽  
Wave Flume

Abstract The generation of two freak waves in a broadband and a narrowband random series registered in the experiments of Li, J. X., Li, P. F., and Liu, S. X. (2013, “Observations of Freak Waves in Random Wave Field in 2D Experimental Wave Flume,” China Ocean Eng., 27(5), pp. 659–670) is precisely reconstructed using a fully non-hydrostatic water wave model. The simulation results indicate that even when the background spectral bandwidths are different, the evolution processes of the two freak waves are similar. Both freak waves emerge quickly during the transition from normal states to extreme events. The freak waves can persist over a long distance, i.e., approximately 5 peak wavelengths. The reconstructed time series in both the backward and forward locations at which the freak waves were recorded reveal that the largest freak wave crests were not captured in the experiment. The freak waves gradually emerged from an intense wave group. The waves developed quickly during the transition from a normal state to an extreme event. Very deep troughs were also formed in the evolution process. The two freak waves were actually generated via different spectral bandwidth processes, but the generation mechanisms of the rogue waves were similar. By analyzing the time series of the freak wave groups, the formation of the freak waves is found to result from the combined effect of the dispersive focusing, the third-order resonant wave interactions, and the higher harmonics.

CFD Study of Air-Gap and Wave Impact Load on Semisubmersible Under Hurricane Conditions

2014 ◽  
Author(s):  
Sing-Kwan Lee ◽  
Kai Yu ◽  
Stanley Chenpey Huang
Keyword(s):  
Impact Load ◽  
Random Wave ◽  
Random Waves ◽  
Extreme Wave ◽  
Regular Waves ◽  
Wave Impact ◽  
Computational Fluid Dynamics Simulations ◽  
The Common ◽  
Run Up ◽  
Dynamics Simulations

CFD (Computational Fluid Dynamics) simulations of airgap and wave impact load on a semisubmersible under extreme wave conditions are performed in this study. Unlike the common practice, in which environmental waves are modeled as regular waves, a random wave series based on a JONSWAP spectrum for a 100-year return wave in the Gulf of Mexico is used to interact with a moored semisubmersible to simulate a more realistic environment condition. Wave run-up and impact loads on a moored semisubmersible due to both regular and random waves are computed and compared to investigate the influence of these different extreme waves on motion and impact load.

Parameterization for Nonlinearity of Random Waves Over Slopes

2013 ◽  
Author(s):  
Hongzhou Chen ◽  
Guohai Dong ◽  
Yuxiang Ma
Keyword(s):  
Coastal Region ◽  
Least Square Method ◽  
Peak Frequency ◽  
Least Square ◽  
Wave Transformation ◽  
Random Wave ◽  
Random Waves ◽  
Nonlinear Characteristics ◽  
Wave Flume ◽  
Physical Experiments

Nonlinearity of gravity waves in coastal region plays crucial role in the wave evolution and the sediment transport. Parameterization of the nonlinear characteristics of random waves is an efficient and important way to descript the wave process. It is well known that coastal topography has a key effect on the wave transformation. However, the related previous studies have ignored the slope effects. It is the primary motivation of the research. To implement this aim, physical experiments of random waves propagating over three slopes (1/15, 1/30, 1/45) were carried out in a wave flume with 50m long, 3m wide and used with a water depth of 0.52m. About 20 random wave simulations based on JONSWAP spectra with varying wave height and peak frequency were considered. The wavelet based bispectrum is adopted to obtain the nonlinear parameters, bicoherence, biphase, skewness and asymmetry. On each slope bottoms, several empirical relationships between these parameters and the local Ursell number are derived using the least square method. The results indicate that the bicoherence and the asymmetry of waves relate to the slope. However, the slopes have negligible effect on the formulae of the skewness. Then, the empirical formulae on the bicoherence and asymmetry combining with the bottom slope are constructed.

scholarly journals Reflection Analysis of Impermeable Slopes under Bimodal Sea Conditions

2020 ◽  
Vol 8 (2) ◽  
pp. 133
Author(s):  
Stephen Orimoloye ◽  
Harshinie Karunarathna ◽  
Dominic E. Reeve
Keyword(s):  
Reflection Coefficient ◽  
Water Depth ◽  
Wave Reflection ◽  
Experimental Tests ◽  
Random Wave ◽  
Reflection Coefficients ◽  
Wave Steepness ◽  
Coastal Structures ◽  
Relative Water ◽  
Reflection Characteristics

Understanding of the reflection characteristics of coastal seawalls is crucial for design. Wave reflection can cause difficulties in small vessel manoeuvring at harbour entrances; this can cause damage to the toe of coastal structures by scouring. Previous studies have examined the reflection characteristics of coastal seawalls under random wind-generated waves without considering the effects of wave bimodality created by the presence of swell waves. This present study focuses on the influence of random wave bimodality on the reflective characteristics of coastal seawalls. 823 experimental tests were conducted to examine the reflection performance of impermeable sloping seawalls under bimodal waves. Reflection coefficients were computed from each test. The analysis of the 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 coefficients of coastal seawalls are strongly influenced by the seawall slope, the wave steepness, the 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 COMPARISON OF DRAG AND INERTIA COEFFICIENTS FOR A CIRCULAR CYLINDER IN RANDOM WAVES DERIVED FROM DIFFERENT METHODS

2011 ◽  
Vol 1 (32) ◽  
pp. 23 ◽  
Author(s):  
Tri Cao Mai ◽  
Mayumi Wilms ◽  
Arndt Hildebrandt ◽  
Torsten Schlurmann
Keyword(s):  
Circular Cylinder ◽  
Random Wave ◽  
Wave Loading ◽  
Random Waves ◽  
Force Coefficients ◽  
Wave Flume ◽  
Wave Kinematics ◽  
Inertia Coefficient ◽  
Line Force ◽  
Experimental Works

This paper presents results from experimental works to investigate wave loading on a vertical circular cylinder in random wave conditions in a wave flume with different water depths . In-line force coefficients (drag and inertia coefficient) are estimated from the measured pressures on cylinder’s surface at different elevations along the length of the cylinder. The wave kinematics are estimated by using different wave theories. Methods of max-min and least-squares (simplified by fit on wave-by-wave basis) are applied to determine force coefficients.

Modelling of Periodic and Random Wave Forces on Submarine Pipelines

2006 ◽  
Author(s):  
Francesco Aristodemo ◽  
Giuseppe R. Tomasicchio ◽  
Paolo Veltri
Keyword(s):  
Numerical Model ◽  
Laboratory Investigation ◽  
Time History ◽  
Hydrodynamic Forces ◽  
Random Wave ◽  
Wave Forces ◽  
Random Waves ◽  
Large Wave ◽  
Wave Flume ◽  
History Of

A numerical model for the prediction of the time variation of the flow field and the hydrodynamic forces on bottom submarine pipelines is proposed. The model is an extension for periodic and random waves of the Wake II hydrodynamic forces model (Soedigdo et al., 1999), originally proposed for sinusoidal waves. An extensive laboratory investigation has been carried out in order to calibrate the model. The numerical model is based on an analysis of the time history of the velocity field at each wave semi-cycle. A modified relationship of the wake velocity is introduced and the time history of the drag and lift hydrodynamic coefficients are obtained using a Gauss integration of the start-up function. The laboratory investigation was performed at the large wave flume of the Centro Sperimentale per Modelli Idraulici at Voltabarozzo (Padua, Italy). The tests were carried out by measuring the pressure values at 8 transducers mounted on a cylinder subjected to different periodic and random waves. The experiments refer to the range 4 ÷ 12 of the Keulegan-Carpenter number for periodic waves and to the range 4 ÷ 9 for random waves. The empirical parameters involved in the extended Wake II and in the classical Morison models were calibrated using the results of the sampled velocities and force time histories under different wave conditions. The comparisons between the experimental and numerical results indicate that the extended Wake II model allows an accurate evaluation of the peaks and of the phase shifts of the horizontal and vertical forces and is more accurate than the Morison model.

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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