Focused wave evolution using linear and second order wavemaker theory

Sriram, V.; Schlurmann, Torsten; Schimmels, Stefan

doi:10.1016/j.apor.2015.09.007

Cited by 53 publications

(37 citation statements)

References 33 publications

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“…Second, the paddle does not have the range of movement required to eliminate sub-harmonic error waves in finite water depth. As a result, error waves were not completely removed by the correction method (see also [49]). Whittaker et al [17] concluded that the sub-harmonic error wave amplitude was reduced by approximately 60% in similar conditions.…”

Section: B Wave Generationmentioning

confidence: 99%

Laboratory study of the wave-induced mean flow and set-down in unidirectional surface gravity wave packets on finite water depth

et al. 2019

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The net movement of Lagrangian particles under water waves comprises a Stokes drift in the direction of wave propagation and an Eulerian return flow in the opposing direction. Accurate prediction of the Eulerian return flow in the ocean is of importance in modelling the transport of plastic pollution, oil, wreckage, and sediment. Herein, we derive a multiple-scales solution for the Eulerian mean flow under wavepackets that is valid for all water depths, both relative to the length of the wave and the length of the wavepacket. To validate this solution, we carry out Particle Tracking Velocimetry experiments in a long flume to extract the mean motion from Lagrangian seeding particles under wavepackets, finding good agreement. The extraction technique is able to deal with small background motion and sub-harmonic error waves associated with wave generation by the paddle, the latter being relatively large in finite-depth flume experiments. In finite depth, the return flow is forced by both the divergence of the Stokes transport on the wavepacket scale and the formation of a non-negligible mean set-down underneath the packet, which acts like a bounding streamtube in the form of a convergent-divergent duct. The magnitude of the horizontal return flow is thus enhanced, with particular relevance to transport in the finite-depth coastal environment.

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Section: B Wave Generationmentioning

confidence: 99%

Laboratory study of the wave-induced mean flow and set-down in unidirectional surface gravity wave packets on finite water depth

et al. 2019

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“…Smith and Swan (2002) also highlighted the importance of nonlinearity and unsteadiness in nu-75 merical simulations of extreme focused waves. Sriram et al (2015) considered the effect of linear and second-order generation signals on focused wave evolution in a parametric study within a physical wave flume. Sriram et al (2015) found that spurious sub-harmonic free waves led to additional focus location shifts, and noted that the effect of such waves was likely to be greater for focus locations closer to the wavemaker.…”

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confidence: 99%

Optimisation of focused wave group runup on a plane beach

Whittaker

Fitzgerald

Raby

et al. 2017

Coastal Engineering

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Insight is provided into focused wave group runup on a plane beach by means of laboratory wave flume experiments and numerical simulations. A focused wave group is presented as an alternative to an empirical description of the wave conditions leading to extreme runup. Secondorder correction to the laboratory wavemaker generation signal is observed to remove about 60% of the sub-harmonic error wave that would otherwise contaminate coastal response experiments. Laboratory measurements of the wave runup time history are obtained using inclined resistancetype wires and copper strips attached to the beach surface. The numerical wave runup model is based on hybrid Boussinesq-Nonlinear Shallow Water equations, empirical parameters for wave breaking and bed friction, and a wetting and drying algorithm. After calibration against experimental runup data, the numerical model reproduces satisfactorily the propagation, shoaling and runup of focused wave groups over the entire length of the wave flume. Results from a comprehensive parametric study show that both measured and predicted maximum runup elevations exhibit strong dependence on the linear focus amplitude of the wave group (linked to its probability of occurrence), the focus location, and the phase of the wave group at focus. The results also demonstrate that extreme runup events owing to focused wave incidence cannot be characterised using spectral parameters alone. The optimal band of focus locations shifts onshore as linear focus amplitude of the incident wave group increases. Optimisation of phase and focus location leads to a maximum runup elevation at each linear amplitude, and, when generated using second-order corrected paddle signals, the maximum runup appears to approach saturation

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“…For example, Orszaghova et al [4] showed that using first-order wavemaker theory could lead to erroneously wave run-up and wave overtopping results compared to generating the waves with second-order wavemaker theory. Furthermore, Sriram et al [5] showed that the breaking point of focused waves is different when using first-order and second-order wavemaker theory. This was expected to be caused by the influence from the free spurious long-wave components generated with first-order theory.…”

Section: Introductionmentioning

confidence: 99%

Applicability of Nonlinear Wavemaker Theory

Eldrup

Andersen

2019

JMSE

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Generation of high-quality waves is essential when making numerical or physically model tests. When using a wavemaker theory outside the validity area, spurious waves are generated. In order to investigate the validity of different wave generation methods, new model test results are presented where linear and nonlinear wave generation theories are tested on regular and irregular waves. A simple modification to the second-order wavemaker theory is presented, which significantly reduces the generation of spurious waves when used outside its range of applicability. For highly nonlinear regular waves, only the ad-hoc unified wave generation based on stream function wave theory was found acceptable. For irregular waves, similar conclusions are drawn, but the modified second-order wavemaker method is more relevant. This is because the ad-hoc unified generation method for irregular waves requires the wave kinematics to be calculated by a numerical model, which might be quite time-consuming. Finally, a table is presented with the range of applicability for each wavemaker method for regular and irregular waves.

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Focused wave evolution using linear and second order wavemaker theory

Cited by 53 publications

References 33 publications

Laboratory study of the wave-induced mean flow and set-down in unidirectional surface gravity wave packets on finite water depth

Laboratory study of the wave-induced mean flow and set-down in unidirectional surface gravity wave packets on finite water depth

Optimisation of focused wave group runup on a plane beach

Applicability of Nonlinear Wavemaker Theory

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