scholarly journals A NEW DESIGN METHOD OF RUBBLE MOUND STRUCTURES

1986 ◽  
Vol 1 (20) ◽  
pp. 161 ◽  
Author(s):  
Cheong-Ro Ryu ◽  
Toru Sawaragi
Keyword(s):  
Design Method ◽  
Wave Train ◽  
Wave Force ◽  
Irregular Waves ◽  
Wave Condition ◽  
Irregular Wave ◽  
The Mean ◽  
Rubble Mound ◽  
Run Up ◽  
Wave Control

A new design method of rubble mound structures with stability and wave control consideration is proposed, by which the reduction of wave reflection and run-up and increase in rubble stability are assured under the given wave conditions. Wave control and stability increasing functions due to change of the slope shape of rubble mound structures are discussed on the basis of the experimental results for regular and irregular waves. The new design formula developed here considered the allowable percentage of damage and the wave grouping effects on rubble stability using a new assumption of the mean run-sum as an index of the irregular wave force. The run-sum is defined as the energy sum of a run satisfying a critical wave condition and the mean run-sum is the mean of run-sum for a irregular wave train.

scholarly journals SIMULATION OF EXTREME WAVE INTERACTION WITH MONOPILE MOUNTS FOR OFFSHORE WIND TURBINES

2012 ◽  
Vol 1 (33) ◽  
pp. 22 ◽  
Author(s):  
Feng Gao ◽  
Clive Mingham ◽  
Derek Causon
Keyword(s):  
Wind Farm ◽  
Wave Interaction ◽  
Wave Force ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Wave Forces ◽  
Extreme Wave ◽  
Irregular Wave ◽  
Run Up

Extreme wave run-up and impacts on monopile foundations may cause unexpected damage to offshore wind farm facilities and platforms. To assess the forces due to wave run-up, the distribution of run-up around the pile and the maximum wave run-up height need to be known. This paper describes a numerical model AMAZON-3D study of wave run-up and wave forces on offshore wind turbine monopile foundations, including both regular and irregular waves. Numerical results of wave force for regular waves are in good agreement with experimental measurement and theoretical results, while the maximum run-up height are little higher than predicted by linear theory and some empirical formula. Some results for irregular wave simulation are also presented.

scholarly journals OVERTOPPING OF RUBBLE-MOUND BREAKWATERS BY IRREGULAR WAVES

1976 ◽  
Vol 1 (15) ◽  
pp. 157
Author(s):  
Yvon Ouellet ◽  
Pierre Eubanks
Keyword(s):  
Wave Train ◽  
The Other ◽  
Irregular Waves ◽  
Regular Wave ◽  
Regular Waves ◽  
Irregular Wave ◽  
Wave Trains ◽  
Rubble Mound ◽  
The Stability ◽  
Rubble Mound Breakwaters

This paper describes the results of an experimental study on the effect of waves on rubble-mound breakwaters, wave transmission subsequent to wave overtopping, the stability of the three sides subjected to wave action and the effect of the breakwaters on waves. Two different rubble-mound breakwaters were tested, i. e. one with a rigid impermeable crest and the other with a flexible permeable crest. Tests were performed with both regular and irregular wave train systems. To obtain the simulated irregular wave trains, four theoretical spectra were chosen: Neumann, Bretschneider, Moskowitz, and Scott. Results obtained from tests with irregular wave trains were compared to those obtained from tests with regular wave trains. It was found that more information was obtained on the behaviour of the structure when it was submitted to the attack of irregular waves than when submitted to regular waves, and that the use of irregular wave trains gave more interesting results.

Irregular Wave and Current Loads on a Fish Farm System

2018 ◽  
Author(s):  
Arnt G. Fredriksen ◽  
Basile Bonnemaire ◽  
Øyvind Nilsen ◽  
Leiv Aspelund ◽  
Andreas Ommundsen
Keyword(s):  
Particle Velocity ◽  
Fish Farm ◽  
Fluid Particle ◽  
Irregular Waves ◽  
Engineering Practice ◽  
Irregular Wave ◽  
Environmental Force ◽  
The Mean ◽  
Particle Velocities ◽  
Farm System

Accurate calculation of the design mooring loads on an aquaculture fish farm mooring system is often a difficult task. The fish farm system has a large horizontal extension with variable environmental conditions across the entire structure. In addition, the drag loads on the fish nets are thought to be the governing environmental force. This means that the mean position of the fish farm is a function of the mean of the fluid particle velocity squared, where the fluid particle velocity must be taken as the sum of current and wave induced fluid particle velocities. Additional offsets will be slowly varying, where the response time will depend on the total mooring stiffness. The magnitudes depend on the height and length on wave groups in the irregular sea state. The paper presents simulations of the response of such a system to a set of combined irregular waves and current conditions. The response evolution in time is discussed as well as parameters affecting the maximum responses in the systems (displacements and loads). Finally, the resulting loads on the fish farm in irregular waves are compared to loads obtained in equivalent regular waves, as this is an often used engineering practice when analyzing the response and mooring loads of a fish farm.

Alternative Methodologies for Subsea Flexible Strength Analysis

2018 ◽  
Author(s):  
Anskey A. Miranda ◽  
Fred P. Turner ◽  
Nigel Barltrop
Keyword(s):  
Real World ◽  
Wave Train ◽  
Irregular Waves ◽  
Wave Crest ◽  
Strength Analysis ◽  
New Wave ◽  
Regular Wave ◽  
Wave Analysis ◽  
Sea State ◽  
Irregular Wave

This paper presents a study of the analysis methodologies used to predict the most likely response of flexibles in a subsea environment, with the aim of determining an efficient and reliable prediction methodology. The most accurate method involves simulating multiple wave realisations of a real world sea state, i.e. irregular waves, and post-processing the results to determine the most probable maximum (MPM). Due to the computationally intensive nature of this approach, however, regular wave analysis is typically used to determine flexible response. This approach considers the maximum wave within a design storm at a desired period; the choice of periods may leave room for uncertainty in the conservatism of the approach. With proper screening, regular wave analysis can be a valid yet overly conservative approach resulting in over design and additional cost. However, if screened incorrectly, there is a possibility that the choice of periods could give results that are under conservative. In addition to regular wave analysis, the paper presents two alternative methodologies to determine the most likely response, with the focus on reducing the computational resources required. The first alternative is an ‘Irregular Wave Screen’ approach in which the wave train is screened at areas of interest for waves within a user defined threshold of the maximum wave height, in addition to other user defined parameters. Only waves within these parameters are simulated to determine responses. The second alternative is the ‘New Wave’ approach, which models the most probable wave elevation around the maximum wave crest. The calculated new wave is then placed at the desired location to determine responses. The responses of the Regular, Irregular Wave Screen and New Wave methodologies are compared with the Irregular MPM approach to determine their feasibility to predict the response of flexibles in a real world irregular sea state with lower computational requirements.

scholarly journals LABORATORY STUDY ON TWO-DIMENSIONAL BEACH TRANSFORMATION DUE TO IRREGULAR WAVES

1986 ◽  
Vol 1 (20) ◽  
pp. 102 ◽  
Author(s):  
Nubuo Mimura ◽  
Yukinori Otsuka ◽  
Akira Watanabe
Keyword(s):  
Wave Train ◽  
Irregular Waves ◽  
Two Dimensional ◽  
Beach Profile ◽  
Irregular Wave ◽  
Sand Ripple ◽  
Ripple Formation ◽  
Sand Movement ◽  
Incident Waves ◽  
Profile Change

In the present study, effects of irregular waves on two-dimensional beach transformation and related phenomena were investigated through a series of laboratory experiments. Attempts were made to determine a representative wave of irregular wave trains which controlled individual phenomenon related to the two-dimensional beach profile change. It was found that the representative wave is different for each phenomenon. For the macroscopic beach profile change, it is the mean wave which represents whole incident waves. On the other hand, some of microscopic phenomena, such as initiation of sand movement and sand ripple formation, are controlled by larger waves in the wave train selectively, of which representative wave is the significant wave.

scholarly journals Study on determination method of hydrodynamic coefficient of Marine pile foundation

2020 ◽  
Vol 143 ◽  
pp. 01021
Author(s):  
Jiang Zongnan
Keyword(s):  
Fourier Analysis ◽  
Time History ◽  
Least Square Method ◽  
Wave Force ◽  
Least Square ◽  
Irregular Waves ◽  
Hydrodynamic Coefficient ◽  
Irregular Wave ◽  
Advantages And Disadvantages ◽  
The Moment

The irregular waves are simulated by using standard spectrum. Instantaneous value method, Fourier analysis method, least square method and "harbour hydrological code" are used to determine the moment force of coefficient CM and drag coefficient CD. Then CM and CD that linearized by Borgman L.E. equation are substituted into Morison equation. The time history curve of the wave force on the pile is calculated and compared with the measured wave force data under the action of irregular wave to analyze the advantages and disadvantages of several methods to determine CM and CD. The results show that the comparison between CM and CD determined by Fourier analysis and least square method is practical.

Numerical Study of Air Gap Response and Wave Impact Load on a Moored Semi-Submersible Platform in Predetermined Irregular Wave Train

2010 ◽  
Author(s):  
Xiufeng Liang ◽  
Jianmin Yang ◽  
Longfei Xiao ◽  
Xin Li ◽  
Jun Li
Keyword(s):  
Impact Load ◽  
Numerical Study ◽  
Wave Train ◽  
Air Gap ◽  
Navier Stokes ◽  
Design Stage ◽  
Wave Impact ◽  
Irregular Wave ◽  
Run Up ◽  
Steep Waves

The importance of understanding air gap response and potential deck impact is well-known in the design stage of semi-submersible platform. The highly non-linear nature of wave elevation around large structures in steep waves makes it difficult to accurately predict wave field under the deck and wave run up along the columns. Present engineering tools for the prediction of air gap response generally based on simplified models. Even the models accounting for nonlinear wave diffraction is not free of uncertainties. A method adopted here couples a Navier-Stokes solver, VOF technique capturing violent free surface and DNV/Seasam predicting motions of moored semi-submersible platform. Air gap response at different locations of the hull was evaluated in predetermined irregular wave train. Wave run up was also measured by wave probes near the columns. Load cells were mounted under the deck of the platform to trace potential deck impact. The predetermined irregular wave train was simulated in a numerical wave tank and verified against physical tank results. Analysis of the air gap response, wave run up and impact loads on the semi-submersible platform were conducted.

A Study for Statistical Characteristics of Riser Response in Global Dynamic Analysis With Irregular Wave

2014 ◽  
Author(s):  
Yanqiu Zhang ◽  
Zhimin Tan ◽  
Yucheng Hou ◽  
Jiabei Yuan
Keyword(s):  
Dynamic Simulation ◽  
Wave Train ◽  
Time History ◽  
Irregular Waves ◽  
Statistical Characteristics ◽  
Normal Process ◽  
Autocorrelation Functions ◽  
Irregular Wave ◽  
Global Dynamic ◽  
Time Histories

A study was conducted to have a deeper understanding to the statistical characteristics of response of flexible riser in global dynamic simulation with irregular wave. If consider the numerical simulation model as a system and the input wave train as an excitation to it, the time histories of riser load should be the response of the system to the excitation. In order to look the effect of riser configuration and water depth, the study was conducted with three kinds of configuration: Free-Hanging, Lazy-S and Tethered-Wave, which were in different water depths. In order to examine the stationarity and ergodicity of riser response, 100 simulations were performed. Each simulation was performed with a 3-hours-long storm. Except the seeds used to generate the random phases to the wave components, the 100 irregular wave processes for each riser are completely the same. When the number of wave components is enough large, the input irregular wave train should be a stationary normal process. Since the software used for the dynamic simulation is high nonlinear, however, the time history of riser response may not be perfectly stationary normal process. Then different probability distribution theories were applied to fit these time histories and the most fitting one was found out for different riser responses and for different riser configurations. The ensemble autocorrelation functions and the time autocorrelation functions were also examined for both irregular waves and the riser responses. Then the study indicated that both irregular waves and riser responses as random processes should be ergodic stationary. Finally the cross correlations between the irregular waves and riser responses were also examined and it was found that the irregular wave for each riser should be jointly stationary with each response of the riser.

scholarly journals Semi-submersible Offshore Coupled Motion in Irregular Waves

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Baoji Zhang ◽  
Ying Wang
Keyword(s):  
Return Period ◽  
Simple Algorithm ◽  
Wave Force ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Offshore Platforms ◽  
Wave Direction ◽  
Motion Response ◽  
Irregular Wave ◽  
Control Equation

In order to predict the hydrodynamic performance of semi-submersible offshore platform accurately, based on CFD theory, continuous equation and N-S equation as the control equation, RNG type k-ε model as turbulence model, using the finite difference method to discretize the control equation，using the Semi-Implicit Method for Pressure Linked Equation (SIMPLE) algorithm to solve the control equation，using the VOF method to capture the free surface. The numerical wave tank of irregular wave is established, and the wave force and motion response of the semi-submersible platform under irregular wave are studied. Based on the Jonswap spectrum density function, for a certain area of two irregular waves (South China sea, a-ten-year return period, a-hundred-year return period) sea condition, five wave direction Angle (0 °, 30 °, 45 °, 60 °, 90 °), a total of 10 kinds of conditions of the motion response of semi-submersible platform are simulated, through analysis and comparison of simulation results, the influence law of wave angle, wave period and wave height on platform motion is obtained. Compared with the experimental values, the results of heave and pitch are close to the experimental data under the sea condition of 2, 0 degree wave angles. The research results in this paper can provide reference for the design and motion response prediction of practical semi-submersible offshore platforms.

scholarly journals Emergence of Solitons from Irregular Waves in Deep Water

2021 ◽  
Vol 9 (12) ◽  
pp. 1369
Author(s):  
Weida Xia ◽  
Yuxiang Ma ◽  
Guohai Dong ◽  
Jie Zhang ◽  
Xiaozhou Ma
Keyword(s):  
Deep Water ◽  
Rogue Wave ◽  
Wave Train ◽  
Irregular Waves ◽  
Peak Wavelength ◽  
Long Distance ◽  
Irregular Wave ◽  
Resonant Interactions ◽  
Dispersion Effects ◽  
Wave Trains

Numerical simulations were performed to study the long-distance evolution of irregular waves in deep water. It was observed that some solitons, which are the theoretical solutions of the nonlinear Schrödinger equation, emerged spontaneously as irregular wave trains propagated in deep water. The solitons propagated approximately at a speed of the linear group velocity. All the solitons had a relatively large amplitude and one detected soliton’s height was two times larger than the significant wave height of the wave train, therefore satisfying the rogue wave definition. The numerical results showed that solitons can persist for a long distance, reaching about 65 times the peak wavelength. By analyzing the spatial variations of these solitons in both time and spectral domains, it is found that the third-and higher-order resonant interactions and dispersion effects played significant roles in the formation of solitons.

Sign in / Sign up

Export Citation Format

Share Document