scholarly journals Predictions of Random Wave Transformation and Near Bottom Velocity in Large Wave Flume Experiments.

1998 ◽  
pp. 145-154 ◽  
Author(s):  
Hajime Mase ◽  
Toshikazu Kitano ◽  
Tomotsuka Takayama
Keyword(s):  
Wave Transformation ◽  
Random Wave ◽  
Flume Experiments ◽  
Large Wave ◽  
Wave Flume

Nonlinear and Dissipative Characteristics of a Combined Random-Cnoidal Wave Field

2017 ◽  
Author(s):  
James M. Kaihatu ◽  
John T. Goertz ◽  
Samira Ardani ◽  
Alex Sheremet
Keyword(s):  
Wave Spectrum ◽  
Leading Edge ◽  
Dissipation Function ◽  
Indian Ocean Tsunami ◽  
Random Wave ◽  
Cnoidal Wave ◽  
State University ◽  
Large Wave ◽  
Wave Flume ◽  
Wave Trains

Images of the 2004 Indian Ocean tsunami at landfall shows a leading edge marked by short waves (“fission” waves). These waves appear to be cnoidal in shape and of a temporal and spatial scale in line with the longest swell present in the region, and may interact with the longer waves in the background random wave spectrum. As part of a comprehensive series of experiments, the Large Wave Flume at Oregon State University (USA) was used to generate and measure the properties of cnoidal, random, and combined cnoidal-random wave trains. Both the nonlinear energy transfer characteristics (via bispectral analysis) and dissipation characteristics (via a proxy dissipation function) are studied for all generated wave conditions. It is generally determined that the characteristics of the cnoidal wave dominate the combined cnoidal-random wave signals if the energy of the cnoidal wave is at least equal to that of the random wave.

scholarly journals High-resolution, large-scale laboratory measurements of a sandy beach and dynamic cobble berm revetment

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Chris E. Blenkinsopp ◽  
Paul M. Bayle ◽  
Daniel C. Conley ◽  
Gerd Masselink ◽  
Emily Gulson ◽  
...  
Keyword(s):  
Large Scale ◽  
Sandy Beach ◽  
Wave Transformation ◽  
Intermediate Water ◽  
Swash Zone ◽  
Laboratory Measurements ◽  
Large Wave ◽  
Water Level Rise ◽  
Wave Flume ◽  
Spatio Temporal

AbstractHigh quality laboratory measurements of nearshore waves and morphology change at, or near prototype-scale are essential to support new understanding of coastal processes and enable the development and validation of predictive models. The DynaRev experiment was completed at the GWK large wave flume over 8 weeks during 2017 to investigate the response of a sandy beach to water level rise and varying wave conditions with and without a dynamic cobble berm revetment, as well as the resilience of the revetment itself. A large array of instrumentation was used throughout the experiment to capture: (1) wave transformation from intermediate water depths to the runup limit at high spatio-temporal resolution, (2) beach profile change including wave-by-wave changes in the swash zone, (3) detailed hydro and morphodynamic measurements around a developing and a translating sandbar.

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.

Multi-Focused Wave Groups in Wave Flume

2019 ◽  
Author(s):  
Qinghe Fang ◽  
Cunbao Zhao ◽  
Anxin Guo
Keyword(s):  
Irregular Waves ◽  
Frequency Resolution ◽  
Random Wave ◽  
Wave Group ◽  
Wave Groups ◽  
Large Wave ◽  
Wave Flume ◽  
Space And Time ◽  
Focused Wave ◽  
Focused Wave Group

Abstract People can simulate extreme hydrodynamic conditions in a laboratory facility by interfering a numbers of regular waves at a certain point in space and time, which is focused wave. It is obviously higher and steeper than any other wave, e.g. regular or irregular waves, within the propagating wave group. The focused wave occurs at a designed point both in space and time. It represents an event with a large return period which would take a long time to reproduce within a random wave sequence. The focused wave, representing of a large wave occurring in a random sea, is quite frequently used to investigate wave loading on marine or coastal structures. However, most research only employ one single focused wave group. Taking the randomness of the wave-structure interaction, repeated tests would be suggested by some textbooks or codes to eliminate the odd results. However, it would take more time to conduct those tests no matter in the laboratory or in the numerical simulations. In our present work, we use a novel method to experimentally generate several focused wave group with different focus time but same focus point at the same time to obtain multi-focused wave groups. The wave elevation and water particle kinematics are measured. The influence of peak frequency, frequency resolution and period of focused wave group are checked and discussed. The results show that present method can generate stable and repeatable focused wave groups in the wave flume.

scholarly journals Efficiency and Survivability of a Floating Oscillating Water Column Wave Energy Converter Moored to the Seabed: An Overview of the EsflOWC MaRINET2 Database

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 992 ◽  
Author(s):  
Dogan Kisacik ◽  
Vasiliki Stratigaki ◽  
Minghao Wu ◽  
Lorenzo Cappietti ◽  
Irene Simonetti ◽  
...  
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Mooring Line ◽  
Oscillating Water Column ◽  
Flume Experiments ◽  
Large Wave ◽  
Wave Flume ◽  
Wave Conditions ◽  
University Of Florence

Floating oscillating water column (OWC) type wave energy converters (WECs), compared to fixed OWC WECs that are installed near the coastline, can be more effective as they are subject to offshore waves before the occurrence of wave dissipation at a nearshore location. The performance of floating OWC WECs has been widely studied using both numerical and experimental methods. However, due to the complexity of fluid–structure interaction of floating OWC WECs, most of the available studies focus on 2D problems with WEC models of limited degrees-of-freedom (DOF) of motion, while 3D mooring effects and multiple-DOF OWC WECs have not been extensively investigated yet under 2D and 3D wave conditions. Therefore, in order to gain a deeper insight into these problems, the present study focuses on wave flume experiments to investigate the motion and mooring performance of a scaled floating OWC WEC model under 2D wave conditions. As a preparatory phase for the present MaRINET2 EsflOWC (efficiency and survivability of floating OWC) project completed at the end of 2017, experiments were also carried out in advance in the large wave flume of Ghent University. The following data were obtained during these experimental campaigns: multiple-DOF OWC WEC motions, mooring line tensions, free surface elevations throughout the wave flume, close to and inside the OWC WEC, change in the air pressure inside the OWC WEC chamber and velocity of the airflow through the vent on top of the model. The tested wave conditions mostly include nonlinear intermediate regular waves. The data obtained at the wave flume of Ghent University, together with the data from the EsflOWC tests at the wave flume of LABIMA, University of Florence, provide a database for numerical validation of research on floating OWC WECs and floating OWC WEC farms or arrays used by researchers worldwide.

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 Large-Scale Laboratory Experiments on Mussel Dropper Lines in Ocean Surface Waves

2020 ◽  
Vol 9 (1) ◽  
pp. 29
Author(s):  
Rebekka Gieschen ◽  
Christian Schwartpaul ◽  
Jannis Landmann ◽  
Lukas Fröhling ◽  
Arndt Hildebrandt ◽  
...  
Keyword(s):  
Large Scale ◽  
Laboratory Experiments ◽  
Blue Mussel ◽  
Farming Systems ◽  
Quality Parameter ◽  
Large Wave ◽  
Marine Aquaculture ◽  
Ocean Surface Waves ◽  
Wave Flume ◽  
Waves And Currents

The rapid growth of marine aquaculture around the world accentuates issues of sustainability and environmental impacts of large-scale farming systems. One potential mitigation strategy is to relocate to more energetic offshore locations. However, research regarding the forces which waves and currents impose on aquaculture structures in such conditions is still scarce. The present study aimed at extending the knowledge related to live blue mussels (Mytilus edulis), cultivated on dropper lines, by unique, large-scale laboratory experiments in the Large Wave Flume of the Coastal Research Center in Hannover, Germany. Nine-months-old live dropper lines and a surrogate of 2.0 m length each are exposed to regular waves with wave heights between 0.2 and 1.0 m and periods between 1.5 and 8.0 s. Force time histories are recorded to investigate the inertia and drag characteristics of live mussel and surrogate dropper lines. The surrogate dropper line was developed from 3D scans of blue mussel dropper lines, using the surface descriptor Abbott–Firestone Curve as quality parameter. Pull-off tests of individual mussels are conducted that reveal maximum attachment strength ranges of 0.48 to 10.55 N for mussels that had medium 3.04 cm length, 1.60 cm height and 1.25 cm width. Mean drag coefficients of CD = 3.9 were found for live blue mussel lines and CD = 3.4 for the surrogate model, for conditions of Keulegan–Carpenter number (KC) 10 to 380, using regular wave tests.

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