scholarly journals WAVE FORCES ON A ROW OF CYLINDRICAL PILES OF LARGE DIAMETER

1978 ◽  
Vol 1 (16) ◽  
pp. 146
Author(s):  
J.C.W. Berkhoff ◽  
J. V.d. Weide
Keyword(s):  
Wave Field ◽  
Numerical Computation ◽  
Large Diameter ◽  
Scattered Wave ◽  
Mutual Interference ◽  
Irregular Waves ◽  
Wave Forces ◽  
Helmholz Equation ◽  
Cylindrical Piles ◽  
Single Piles

In order to determine wave forces on a row of three cylindrical piles (Figure 2), a numerical computation procedure was applied using a solution of the Helmholz equation, in which the scattered wave field is described as the result of a series of singular sources located along the circumference of the pile [^Berkhoff, 1976, reference lj . Results of the computations were verified by means of model experiments, using both regular and irregular waves. It is shown that for the two pile geometries, included in the study, strong mutual interference will occur, resulting in transverse forces which are much higher than those found for single piles.

scholarly journals WAVE FORCES INDUCED BY IRREGULAR WAVES ON A VERTICAL CIRCULAR CYLINDER

1978 ◽  
Vol 1 (16) ◽  
pp. 144 ◽  
Author(s):  
Hajime Ishida ◽  
Yuichi Iwagaki
Keyword(s):  
Circular Cylinder ◽  
Laboratory Experiments ◽  
Large Diameter ◽  
Small Diameter ◽  
Diffraction Theory ◽  
Irregular Waves ◽  
Wave Forces ◽  
Irregular Wave ◽  
Water Level Variations ◽  
Particle Velocities

In order to examine the irregular wave forces on a small diameter cylinder, laboratory experiments have been conducted on water particle velocities and wave forces with various kinds of irregular waves. As the results, it is indicated that the time variation and the spectral distribution of wave forces can be calculated adequately from the water level variations by using the methods proposed by Reid1' and Borgman2' respectively. Moreover, with respect to the irregular wave forces on a large diameter cylinder, a new calculation method was shown by means of applying Reid's linear filters1' to MacCamy and Fuchs's diffraction theory.

scholarly journals CFD Simulations of Multi-Directional Irregular Wave Interaction With a Large Cylinder

2018 ◽  
Author(s):  
Weizhi Wang ◽  
Arun Kamath ◽  
Hans Bihs
Keyword(s):  
Wave Field ◽  
Ocean Waves ◽  
Irregular Waves ◽  
Wave Forces ◽  
Good Prediction ◽  
Wave Steepness ◽  
Coastal Structures ◽  
Regular Waves ◽  
Irregular Wave ◽  
Large Cylinder

Ocean waves are random by nature and can be regarded as a superposition of a finite number of regular waves travelling in different directions with different frequencies and phases. Cylinder-shaped objects are commonly present in most coastal structures. An irregular bottom topography has a significant influence on the wave behaviours and therefore the wave forces on the coastal structures. A numerical approach that is able to calculate the wave forces on a cylinder in a multi-directional irregular wave field over an irregular bottom is desired. As Computational Fluid Dynamics (CFD) is able to represent most of the wave behaviour with few assumptions, it is considered to be an attractive option to address these issues. The open-source CFD wave model REEF3D has shown good performances in simulating wave propagation over irregular bottoms and a good prediction of wave forces on a cylinder in a uni-directional wave field, yet the ability to calculate the wave force in a multi-directional irregular sea needs to be validated. Therefore, this paper attempts to simulate the multi-directional random sea interaction with a large cylinder using REEF3D and validate the results. A novel approach of multi-directional irregular wave generation method in a CFD-based numerical wave tank is introduced. Only even-bottom tanks are considered in this study, leaving the irregular bottom simulation for future studies. Furthermore, among many factors that influence the wave forces, this paper focuses particularly on the effect of the wave steepness. The effects of wave steepness in regular waves, uni-directional irregular waves and multi-directional irregular waves are investigated. Goda’s JONSWAP frequency spectrum and the frequency-independent Mitsuyasu directional spreading function are used to generate the multi-directional irregular waves. The wave forces due to the multi-directional irregular waves in the numerical tank are compared with experimental data. The performance of the CFD simulation is analysed and discussed.

Interaction of High Frequency Lamb Waves with Surface-Mount Sensor Adhesives

2013 ◽  
Vol 558 ◽  
pp. 489-500 ◽  
Author(s):  
Patrick Norman ◽  
Claire Davis ◽  
Cédric Rosalie ◽  
Nik Rajic
Keyword(s):  
Wave Field ◽  
Lamb Waves ◽  
Base Material ◽  
Adhesive Layer ◽  
Scattered Wave ◽  
Phase Lag ◽  
Wave Fields ◽  
Surface Mount ◽  
Frequency Regime ◽  
Fibre Bragg Gratings

The application of Lamb waves to damage and/or defect detection in structures is typicallyconfined to lower frequencies in regimes where only the lower order modes propagate in order to simplifyinterpretation of the scattered wave-fields. Operation at higher frequencies offers the potentialto extend the sensitivity and diagnostic capability of this technique, however there are technical challengesassociated with the measurement and interpretation of this data. Recent work by the authorshas demonstrated the ability of fibre Bragg gratings (FBGs) to measure wave-fields at frequencies inexcess of 2 MHz [1]. However, when this work was extended to other thinner plate specimens it wasfound that at these higher frequencies, the cyanoacrylate adhesive (M-Bond 200) used to attach theFBG sensors to the plate was significantly affecting the propagation of the waves. Laser vibrometrywas used to characterise the wave-field in the region surrounding the adhesive and it was found that theself-adhesive retro-reflective tape applied to aid with this measurement was also affecting the wavefieldin the higher frequency regime. This paper reports on an experimental study into the influence ofboth of these materials on the propagating wave-field. Three different lengths of retro-reflective tapewere placed in the path of Lamb waves propagating in an aluminium plate and laser vibrometry wasused to measure the wave-field upstream and downstream of the tape for a range of different excitationfrequencies. The same experiment was conducted using small footprint cyanoacrylate film samplesof different thickness. The results show that both of these surface-mount materials attenuate, diffractand scatter the incoming waves as well as introducing a phase lag. The degree of influence of thesurface layer appears to be a function of its material properties, the frequency of the incoming waveand the thickness and footprint of the surface layer relative to the base material thickness. Althoughfurther work is required to characterise the relative influence of each of these variables, investigationsto date show that for the measurement of Lamb Waves on thin structures, careful considerationshould be given to the thickness and footprint of the adhesive layer and sensor, particularly in the highfrequency regime, so as to minimise their effect on the measurement.

Seismic Waves in a Laterally Inhomogeneous Layered Medium, Part I: Theory

1997 ◽  
Vol 64 (1) ◽  
pp. 50-58 ◽  
Author(s):  
Ruichong Zhang ◽  
Liyang Zhang ◽  
Masanobu Shinozuka
Keyword(s):  
Wave Field ◽  
Half Space ◽  
Seismic Waves ◽  
Scattered Wave ◽  
Inhomogeneous Layer ◽  
Dislocation Source ◽  
Seismic Dislocation ◽  
Body Forces ◽  
The Mean ◽  
Layered Half Space

Seismic waves in a layered half-space with lateral inhomogeneities, generated by a buried seismic dislocation source, are investigated in these two consecutive papers. In the first paper, the problem is formulated and a corresponding approach to solve the problem is provided. Specifically, the elastic parameters in the laterally inhomogeneous layer, such as P and S wave speeds and density, are separated by the mean and the deviation parts. The mean part is constant while the deviation part, which is much smaller compared to the mean part, is a function of lateral coordinates. Using the first-order perturbation approach, it is shown that the total wave field may be obtained as a superposition of the mean wave field and the scattered wave field. The mean wave field is obtainable as a response solution for a perfectly layered half-space (without lateral inhomogeneities) subjected to a buried seismic dislocation source. The scattered wave field is obtained as a response solution for the same layered half-space as used in the mean wave field, but is subjected to the equivalent fictitious distributed body forces that mathematically replace the lateral inhomogeneities. These fictitious body forces have the same effects as the existence of lateral inhomogeneities and can be evaluated as a function of the inhomogeneity parameters and the mean wave fleld. The explicit expressions for the responses in both the mean and the scattered wave fields are derived with the aid of the integral transform approach and wave propagation analysis.

Ocean Wave Forces on Circular Cylindrical Piles

1957 ◽  
Vol 83 (2) ◽  
Author(s):  
R. L. Wiegel ◽  
K. E. Beebe ◽  
James Moon
Keyword(s):  
Ocean Wave ◽  
Wave Forces ◽  
Cylindrical Piles

Experimental Study of Wave Force Distribution on a Monopile Structure

2018 ◽  
Author(s):  
Malene H. Vested ◽  
Stefan Carstensen ◽  
Erik Damgaard Christensen
Keyword(s):  
Experimental Studies ◽  
Cost Effective ◽  
Wave Force ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Force Distribution ◽  
Wave Forces ◽  
Total Force ◽  
Wave Flume ◽  
Effective Manner

As the demand for offshore wind energy continues to grow, the strive to understand the wave forces acting on the substructure of the wind turbines continues. In regard to wind turbine design, it is vital to consider not only the total wave force, but also the local wave forces. Local forces are particularly important for the design of secondary structures as e.g. mooring platforms. Typically, however, experimental studies mainly concern total forces or idealized local forces. We present here a rather simple way to measure local forces along a model monopile. The study is conducted in a wave flume of 28 m in length, in which waves are generated by a piston-type wave maker at a water depth of 0.515 m and shoal onto a bed of slope 1:25. A model monopile is installed and subjected to forcing from a series of both regular and irregular waves. In the experimental set-up, the model monopile is fixed at the bottom and the top and consists of seven independent cylindrical sections. The cylindrical sections are connected by force transducers which measure local shear, and so the associated local forces may be determined. The measured local forces are compared to the force distribution given by Morisons equation combined with linear theory and Wheeler stretching, which is a force estimate commonly used in the industry. This study shows that the total force is rather well captured by Morison’s equation. The force distribution estimated from Morison’s equation, however, shows larger discrepancies from the measured forces. This encourages for further measurements. In this study, we show that it is possible to measure force distribution on a model monopile in a simple and cost-effective manner. The aim is here to demonstrate the method and we will later present a larger body of work associated with the outcome of the measurements.

On Approximations of the Wave Drift Forces Acting on Semi-Submersible Platforms With Heave Plates

2016 ◽  
Author(s):  
Bernard Molin ◽  
Jean-Baptiste Lacaze
Keyword(s):  
Wave Field ◽  
Scattered Wave ◽  
Diffraction Radiation ◽  
Morison Equation ◽  
Wave Drift ◽  
Horizontal Wave ◽  
Heave Plate ◽  
Drift Force ◽  
Wave Drift Forces ◽  
Drift Forces

The horizontal wave drift force acting on a vertical floating column, without then with a heave plate, is considered. Computations are performed with a diffraction-radiation code and through the Morison and Rainey equations. Focus is on wave frequencies around the heave resonance where the drift force may be significant, even though the scattered wave-field being weak. It is found that the Morison equation overpredicts the drift force while Rainey equations perform rather well.

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