Prediction of Surface Wave Elevation Based on Pressure Measurements

1999 ◽  
Vol 121 (4) ◽  
pp. 242-250 ◽  
Author(s):  
E. Meza ◽  
J. Zhang ◽  
R. J. Seymour
Keyword(s):  
Wave Train ◽  
Wave Model ◽  
Wave Theory ◽  
Linear Wave ◽  
Pressure Measurements ◽  
Transient Wave ◽  
Irregular Wave ◽  
Wave Elevation ◽  
Modulation Methods ◽  
Elevation Measurement

A deterministic method for predicting wave elevation based on pressure measurements is developed. The method is based on the hybrid wave model (HWM), which employs both conventional and phase modulation methods for modeling wave-wave interactions in an irregular wave train. The predicted wave elevation using the HWM based on the pressure measurement of a steep transient wave train is in excellent agreement with the corresponding elevation measurement, while that using linear wave theory (LWT) has relatively large discrepancies.

Irregular Wave Forces on Monopile Foundations: Effect of Full Nonlinearity and Bed Slope

2011 ◽  
Author(s):  
Signe Schlo̸er ◽  
Henrik Bredmose ◽  
Harry B. Bingham
Keyword(s):  
Stream Function ◽  
Function Theory ◽  
Wave Train ◽  
Wave Theory ◽  
Irregular Waves ◽  
Wave Forces ◽  
Linear Wave ◽  
Irregular Wave ◽  
Bed Slope ◽  
Force Profiles

Forces on a monopile from a nonlinear irregular unidirectional wave model are investigated. Two seabed profiles of different slopes are considered. Morison’s equation is used to investigate the forcing from fully nonlinear irregular waves and to compare the results with those obtained from linear wave theory and with stream function wave theory. The latter of these theories is only valid on a flat bed. The three predictions of wave forces are compared and the influence of the bed slope is investigated. Force-profiles of two selected waves from the irregular wave train are further compared with the corresponding force-profiles from stream function theory. The results suggest that the nonlinear irregular waves give rise to larger extreme wave forces than those predicted by linear theory and that a steeper bed slope increases the wave forces both for linear and nonlinear waves. It is further found that stream function theory in some cases underestimate the wave forces acting on the monopile.

scholarly journals A SIMPLE AND ACCURATE NONLINEAR METHOD FOR RECOVERING THE SURFACE WAVE ELEVATION FROM PRESSURE MEASUREMENTS

2018 ◽  
pp. 46
Author(s):  
Philippe Bonneton ◽  
Arthur Mouragues ◽  
David Lannes ◽  
Kevin Martins ◽  
Hervé Michallet
Keyword(s):  
Surface Wave ◽  
Measurement Errors ◽  
Pressure Sensors ◽  
Wave Theory ◽  
Linear Wave ◽  
Nonlinear Method ◽  
Nonlinear Phase ◽  
Wave Elevation ◽  
Measuring Surface ◽  
Wave Models

Near-bottom-mounted pressure sensors have long been used for measuring surface wave in the nearshore. The commonly used practice is to recover the wave field by means of a transfer function based on linear wave theory (e.g. Guza and Thornton, 1980; Bishop and Donelan, 1987). However, wave nonlinearities can be strong in the shoaling zone, especially in the region close to the onset of breaking, and thus the use of a linear theory can be questioned. Martins et al. (2017) and Bonneton (2017, 2018) have shown that the linear reconstruction fails to describe the peaky and skewed shape of nonlinear waves prior to breaking, with wave height errors up to 30%. Such measurement errors are problematic for many coastal applications. For instance, studies on wave overtopping and submersion require accurate measurements of the highest wave crests. Furthermore, a correct description of wave asymmetry and skewness is of paramount importance for understanding sediment dynamics. Finally, an accurate description of the wave elevation field is also crucial for the validation of the new generation of fully-nonlinear phase-resolving wave models.

Reconstruction of Ocean Surfaces From Randomly Distributed Measurements Using a Grid-Based Method

2021 ◽  
Author(s):  
Nicolas Desmars ◽  
Moritz Hartmann ◽  
Jasper Behrendt ◽  
Marco Klein ◽  
Norbert Hoffmann
Keyword(s):  
Wave Model ◽  
Wave Theory ◽  
Linear Wave ◽  
Surface Dynamics ◽  
Wave Measurements ◽  
Model Parameterization ◽  
Grid Points ◽  
High Flexibility ◽  
Similar Accuracy ◽  
Grid Based

Abstract In view of deterministic ocean wave prediction, we introduce and investigate a new method to reconstruct ocean surfaces based on randomly distributed wave measurements. Instead of looking for the optimal parameters of a wave model through the minimization of a cost function, our approach directly solves the free surface dynamics — coupled with an interpolation operator — for the quantities of interest (i.e., surface elevation and velocity potential) at grid points that are used to compute the relevant operators. This method allows a high flexibility in terms of desired accuracy and ensures the physical consistency of the solution. Using the linear wave theory and unidirectional wave fields, we validate the applicability of the proposed method. In particular, we show that our grid-based method is able to reach similar accuracy than the wave-model parameterization method at a reasonable cost.

Numerical Non-Reflecting Irregular Wave Flume Based on VOF Method

2009 ◽  
Author(s):  
Bing Ren ◽  
Xuelin Li ◽  
Peng Han ◽  
Yongxue Wang
Keyword(s):  
Wave Theory ◽  
Vof Method ◽  
Numerical Results ◽  
Irregular Waves ◽  
Open Boundary ◽  
Linear Wave ◽  
Reflected Waves ◽  
Irregular Wave ◽  
Wave Flume ◽  
Sponge Layer

A numerical irregular wave flume is developed using VOF method in conjunction with Reynolds equations. An active absorbing wave-maker based on linear wave theory is set on the left boundary of the wave flume to absorb the re-reflected waves. A sponge layer is set on the open boundary to absorb the outgoing waves. The numerical results of regular and irregular waves using the active absorbing-generating boundary are compared to the numerical results using the ordinary generating boundary to verify the performance of the active absorbing-generator boundary. The linear damping coefficient is used in the sponge layer. The damping characteristics of the sponger layer implemented in the wave flume are discussed. The computed wave spectra are compared with the target spectra.

scholarly journals THE MEASURED PROPERTIES OF IRREGULAR WAVE BREAKING AND WAVE HEIGHT CHANGE AFTER BREAKING ON THE SLOPE

1988 ◽  
Vol 1 (21) ◽  
pp. 29 ◽  
Author(s):  
Akira Seyama ◽  
Akira Kimura
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Wave Theory ◽  
Irregular Waves ◽  
Linear Wave ◽  
Periodic Waves ◽  
Zero Crossing ◽  
Irregular Wave ◽  
Height Change ◽  
Cross Waves

Wave height change of the zero-down-cross waves on uniform slopes were examined experimentally. The properties of shoaling, breaking and decay after breaking for a total of about 4,000 irregular waves of the Pierson-Moskowitz type on 4 different slopes (1/10, 1/20, 1/30 and 1/50) were investigated. The shoaling property of the zero-down-cross waves can be approximated by the linear wave theory. However, the properties of breaking and decay after breaking differ considerably from those for periodic waves. The wave height water depth ratio (H/d) at the breaking point for the zero-down-cross waves is about 30% smaller than that for periodic waves on average despite the slopes. Wave height decay after breaking also differs from that for periodic waves and can be classified into three regions, i.e. shoaling, plunging and bore regions. Experimental equations for the breaking condition and wave height change after breaking are proposed in the study. A new definition of water depth for the zero-crossing wave analysis which can reduce the fluctuation in the plotted data is also proposed.

A Phase-Amplitude Iteration Scheme for the Optimization of Deterministic Wave Sequences

2009 ◽  
Author(s):  
Christian Schmittner ◽  
Sascha Kosleck ◽  
Janou Hennig
Keyword(s):  
Target Location ◽  
Wave Train ◽  
Target Position ◽  
Wave Theory ◽  
Iteration Scheme ◽  
Linear Wave ◽  
Linear Wave Theory ◽  
Wave Basin ◽  
Wave Maker ◽  
Phase Amplitude

For the deterministic investigation of extreme events like capsizing, broaching or wave impacts, methods for the generation of deterministic wave sequences are required. These wave sequences can be derived from full scale measurements, numerical simulations or other sources. Most methods for the generation of deterministic wave sequences rely as a backbone on linear wave theory for the backwards transformation of the wave train from the target position in the wave basin to the position of the wave maker. This implies that nonlinear wave effects are not covered to full extend or they are completely neglected. This paper presents a method to improve the quality of the generated wave train via an experimental optimization. Based on a first wave sequence generated with linear wave theory and measured in the wave basin, the phases and amplitudes of the wave maker control signal are modified in frequency domain. The iteration scheme corrects both, shifts in time and in location, resulting in an improved deterministic wave train at the target location. The paper includes results of this method from three different basins with different types of wave generators, water depth and model scales. In addition, this method is applied to a numerical wave tank where the waves can be optimized before the actual basin testing.

Extraction of Harmonic Components From Intermittent and Aperiodic Wave Elevation Measurements

2012 ◽  
Author(s):  
Wenlong Yang ◽  
Sau-Lon James Hu ◽  
Huajun Li
Keyword(s):  
Least Squares Method ◽  
Fourier Method ◽  
Harmonic Component ◽  
Time History ◽  
Second Step ◽  
Sea Waves ◽  
Irregular Wave ◽  
Wave Elevation ◽  
Harmonic Components ◽  
Elevation Measurement

Sea waves never repeat so any measurement of irregular wave elevation time history should be treated as an aperiodic function. Furthermore, wave elevation measurements might also be intermittent. The objective of this study is to extract harmonic components from an aperiodic and intermittent wave elevation measurement. A mathematically sound method, which is completely different from the traditional Fourier method, is developed for extracting all harmonic components from an aperiodic and intermittent wave elevation measurement. The method involves two main steps. In the first step, the number of harmonic components in the wave elevation measurement and the frequency of each component are estimated. After knowing the frequencies, the amplitude and phase angle of each harmonic component are computed at the second step using a least squares method. The superiority of the newly developed method over the traditional DFT analysis on extracting harmonic components is demonstrated using simulated aperiodic wave elevation signals. Whereas using the proposed method can nicely recover all target harmonic components, the Fourier analysis fails to decompose the signal into the target harmonic components due to its periodicity assumption imposed on the aperiodic wave elevation signal. In addition, the new method also performs well with a simulated aperiodic/intermittent wave elevation signal, and can accurately recover the missing part of the aperiodic/intermittent signal.

scholarly journals Phase-Resolved Reconstruction Algorithm and Deterministic Prediction of Nonlinear Ocean Waves From Spatio-Temporal Optical Measurements

2018 ◽  
Author(s):  
Nicolas Desmars ◽  
Yves Pérignon ◽  
Guillaume Ducrozet ◽  
Charles-Antoine Guérin ◽  
Stephan T. Grilli ◽  
...  
Keyword(s):  
Free Surface ◽  
Wave Model ◽  
Reconstruction Algorithm ◽  
Wave Theory ◽  
Ocean Waves ◽  
Optical Measurements ◽  
Linear Wave ◽  
Offshore Structure ◽  
Highly Nonlinear ◽  
Spatio Temporal

We investigate a nonlinear phase-resolved reconstruction algorithm and models for the deterministic prediction of ocean waves based on a large number of spatio-temporal optical measurements of surface elevations. We consider a single sensor (e.g., LIDAR, stereo-video, etc.) mounted on a fixed offshore structure and remotely measuring fields of free surface elevations. Assuming a uniform distribution of measurement points over the sensor aperture angles, the density of free surface observation points geometrically decreases with the distance from the sensor. Additionally, wave shadowing effects occur, which become more important at small viewing angles (i.e., grazing incidence on the surface). These effects result in observations of surface elevation that are sparsely distributed. Here, based on earlier work by [1], we present and discuss the characteristics of an algorithm, aimed at assimilating such sparse data and able to deterministically reconstruct and propagate ocean surface elevations for their prediction in time and space. This algorithm could assist in the automatic steering and control of a variety of surface vehicles. Specifically, we compare prediction results using linear wave theory and the weakly nonlinear Choppy Wave Model [2, 3], extended here to an “improved” second order formulation. The latter model is based on an efficient Lagrangian formulation of the free surface and was shown to be able to model wave properties that are important to the proper representation of nonlinear free surfaces, namely wave shape and celerity. Synthetic datasets from highly nonlinear High Order Spectral simulations are used as reference oceanic surfaces. Predicted results are analyzed over an area that evolves in time, using the theoretical amount of information assimilated during the reconstruction of the wave field. For typical horizons of prediction, we discuss the capabilities of our assimilation process for each wave model considered.

scholarly journals COUPLING STOKES AND CNOIDAL WAVE THEORIES IN A NONLINEAR REFRACTION MODEL

1988 ◽  
Vol 1 (21) ◽  
pp. 42
Author(s):  
Thomas A. Hardy ◽  
Nicholas C. Kraus
Keyword(s):  
Nonlinear Refraction ◽  
Wave Model ◽  
Wave Theory ◽  
Quantitative Agreement ◽  
Wave Mode ◽  
Finite Amplitude ◽  
Second Order ◽  
Stokes Wave ◽  
Linear Wave ◽  
Cnoidal Wave

An efficient numerical model is presented for calculating the refraction and shoaling of finite-amplitude waves over an irregular sea bottom. The model uses third-order Stokes wave theory in relatively deep water and second-order cnoidal wave theory in relatively shallow water. It can also be run using combinations of lower-order wave theories, including a pure linear wave mode. The problem of the connection of Stokes and cnoidal theories is investigated, and it is found that the use of second-order rather than first-order cnoidal theory greatly reduces the connection discontinuity. Calculations are compared with physical model measurements of the height and direction of waves passing over an elliptical shoal. The finite-amplitude wave model gives better qualitative and quantitative agreement with the measurements than the linear model.

Effect of High-Frequency Response on TLP Tendon Fatigue

2012 ◽  
Author(s):  
Edmund Muehlner ◽  
Surya Banumurthy ◽  
John Murray
Keyword(s):  
Frequency Response ◽  
Fatigue Damage ◽  
High Frequency ◽  
Wave Model ◽  
Wave Theory ◽  
Domain Model ◽  
Linear Wave ◽  
Analysis Model ◽  
Linear Wave Theory ◽  
High Frequency Response

High-frequency vibrations of Tension Leg Platforms (TLPs), commonly known as ringing and springing, have challenged TLP designers since the first full-scale TLP was installed in the North Sea in 1984. Although current design codes recognize the significance of the ringing and springing response for tendon design, no widely accepted modeling approach for their calculation has yet emerged. This paper presents a nonlinear time-domain model of a TLP that exhibits the ringing and springing response of the vessel. The analysis model uses large displacement theory for the vessel and tendons and a semi-empirical wave model based on a modified linear wave theory. Predictions of vessel motions and tendon loads made with the analysis model were compared to model tests and were found in good agreement with the measurements. The analysis model was also was used to investigate the fatigue damage in the tendons caused by the vessel’s high-frequency response. Tendon stress time histories were computed for nine different unidirectional sea-states. These sea-states represent a condensed wave scatter diagram for the Gulf of Mexico (GoM). The tendon fatigue was calculated from the stress histories by rainflow counting. Fatigue contributions from different frequency ranges were identified by Fourier analysis. The analysis showed that high-frequency response was present in all sea-states even though ringing occurred only in sea-states with significant wave heights above 10 ft. Tendon fatigue damage contribution from high-frequency loads were found to be significant in every sea-state. For all sea-states combined 73% of the up-wave tendon fatigue damage was due to high-frequency response. For the down-wave and the cross-wave tendons, the high-frequency contributions were 57% and 34%, respectively. This paper demonstrates the importance of considering high-frequency response for the fatigue design of TLP tendons. Another finding of the study is that the analysis model using a modified linear wave theory can describe the ringing and springing behavior of a TLP provided other significant nonlinearities of the system are considered.

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