A Model for Long-Term Distribution of Wave Induced Loads in Steep and Breaking Shallow Water Waves

2012 ◽  
Author(s):  
Hans Fabricius Hansen ◽  
Iris Pernille Lohmann ◽  
Jacob Tornfeldt Sørensen ◽  
Flemming Schlütter
Keyword(s):  
Transfer Function ◽  
Shallow Water ◽  
Wave Height ◽  
Wave Breaking ◽  
Extreme Value Analysis ◽  
Offshore Wind Turbine ◽  
Height Distribution ◽  
Wave Load ◽  
Wave Induced

A new approach to determine the design wave load on bottom-fixed structures in shallow water breaking waves is presented here. The method takes into account the effects that wave breaking has on both the wave height distribution and the wave induced loads on the structure. The loads on offshore wind turbine foundations in irregular seas with a significant amount of wave breaking are modeled in a physical wave tank. The loads are related to wave characteristics as steepness and Ursell number, and a non-linear transfer function between wave height/period and wave load is established. Characteristic historical load events are now established by combining the transfer function with a record of the wave climate at the site. The latter is taken from a hindcast database, but could also come from site measurements. The long-term distribution of the load is estimated by adopting traditional extreme value analysis techniques to the historical characteristic loads.

scholarly journals WAVE HEIGHT DISTRIBUTION IN CONSTANT AND FINITE DEPTHS

2012 ◽  
Vol 1 (33) ◽  
pp. 15 ◽  
Author(s):  
Sofia Caires ◽  
Marcel R.A. Van Gent
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Wave Breaking ◽  
Rayleigh Distribution ◽  
Height Distribution ◽  
High Wave ◽  
Wave Height Distribution ◽  
Individual Wave ◽  
Wave Heights

Several alternatives to the Rayleigh distribution have been proposed for describing individual wave heights in regions where depth-induced wave breaking occurs. The most widely used of these is the so-called Battjes and Groenendijk distribution. This distribution has been derived and validated in a context of a shallow water foreshore waves propagating over a gently sloping shallow region towards the shore. Its validity for waves propagating in regions with shallow flat bottoms is investigated here. It is concluded that the distribution on average underestimates (outside its range of validity) high wave height measurements in shallow flat bottoms by as much as 15%.

scholarly journals RELATION BETWEEN SHAPE OF EXTREME WAVE HEIGHT DISTRIBUTIONS AND WEATHER SYSTEM

2018 ◽  
pp. 73
Author(s):  
Maki Chiwata ◽  
Tomoya Shimura ◽  
Nobuhito Mori
Keyword(s):  
Wave Height ◽  
Extreme Value ◽  
Structure Design ◽  
Extreme Value Analysis ◽  
Observation Data ◽  
Height Distribution ◽  
Extreme Wave ◽  
Engineering Applications ◽  
Value Analysis

The extreme value analysis of wave height has been used to estimate design value of coastal structure design. The procedure of extreme value analysis is standardized but distributions change highly depending on target locations. A long-term atmospheric reanalysis is useful for engineering applications to complement observation data. Although the reanalysis dataset was insufficient for coastal engineering applications due to shorter length of period and sparse spatial resolution of modeling, recent reanalysis (e.g. CFSR) give reasonable performance for engineering applications as wave climate both accuracy and length of periods (e.g. Menendez and Losada, 2017). This study analyzes characteristics of extreme wave heights and understands relation between extreme wave height distribution and its dependence on weather systems based on long-term analysis and observed data.

Irregular Wave Loads on a Gravity Based Foundation in Shallow Water

2011 ◽  
Author(s):  
Erik D. Christensen ◽  
Iris P. Lohmann ◽  
Hans F. Hansen ◽  
Piet Haerens ◽  
Peter Mercelis ◽  
...  
Keyword(s):  
Time Series ◽  
Shallow Water ◽  
Wave Breaking ◽  
Wave Loads ◽  
Wave Load ◽  
Foundation Design ◽  
Wave Condition ◽  
Irregular Wave ◽  
Run Up ◽  
Wave Induced

In order to achieve a safe but cost-effective foundation design of offshore structures, it is important to include effects of run-up and wave breaking in the estimation of wave loads on structures in relatively shallow water. This study presents results from a method applied to estimate wave loads on a gravity based foundation (GBF) coming from irregular waves which are potentially subjected to wave breaking. The objective of the study is to analyse the loads on gravity based foundations for wind turbines on the Thornton Bank, Belgium, due to irregular breaking waves. This study focuses on uncertainties in estimation of maximum loads based on the same wave condition, i.e. (Hs, Tp, Wave Spectrum). To this end three different synthetic irregular wave time series elaborated from the same wave condition are used to simulate the wave load on the GBF. The simulations result in time-series of wave loads and wave elevations on the GBF. The loads obtained from the model indicate a small difference (below 10% in peak values) between the wave-induced inline force for the three simulations, and differences up to 15–20% on the peak values of the obtained wave induced overturning moments. From the simulation results it is also possible to investigate flow patterns and run-up around the structure.

scholarly journals A numerical model for simulation of near-shore waves and wave induced currents using the depth-averaged non-hydrostatic shallow water equations with an improvement of wave energy dissipation

2020 ◽  
Vol 20 (2) ◽  
pp. 155-172
Author(s):  
Phung Dang Hieu ◽  
Phan Ngoc Vinh
Keyword(s):  
Numerical Model ◽  
Shallow Water ◽  
Wave Height ◽  
Shallow Water Equations ◽  
Wave Breaking ◽  
Water Model ◽  
Height Distribution ◽  
Time Duration ◽  
Wave Energy Dissipation ◽  
Near Shore

This study proposes a numerical model based on the depth-integrated non-hydrostatic shallow water equations with an improvement of wave breaking dissipation. Firstly, studies of parameter sensitivity were carried out using the proposed numerical model for simulation of wave breaking to understand the effects of the parameters of the breaking model on wave height distribution. The simulated results of wave height near the breaking point were very sensitive to the time duration parameter of wave breaking. The best value of the onset breaking parameter is around 0.3 for the non-hydrostatic shallow water model in the simulation of wave breaking. The numerical results agreed well with the published experimental data, which confirmed the applicability of the present model to the simulation of waves in near-shore areas.

scholarly journals Long-Term and Seasonal Trends in Global Wave Height Extremes Derived from ERA-5 Reanalysis Data

2020 ◽  
Vol 8 (12) ◽  
pp. 1015
Author(s):  
Alicia Takbash ◽  
Ian R. Young
Keyword(s):  
Southern Hemisphere ◽  
Wave Height ◽  
Significant Wave Height ◽  
Reanalysis Data ◽  
Extreme Value Analysis ◽  
Winter Storms ◽  
Value Analysis ◽  
Weather Forecasts ◽  
Significant Wave

A non-stationary extreme value analysis of 41 years (1979–2019) of global ERA5 (European Centre for Medium-Range Weather Forecasts Reanalysis) significant wave height data is undertaken to investigate trends in the values of 100-year significant wave height, Hs100. The analysis shows that there has been a statistically significant increase in the value of Hs100 over large regions of the Southern Hemisphere. There have also been smaller decreases in Hs100 in the Northern Hemisphere, although the related trends are generally not statistically significant. The increases in the Southern Hemisphere are a result of an increase in either the frequency or intensity of winter storms, particularly in the Southern Ocean.

Effects of Cnoidal Wave-Induced Seepage on Vertical Breakwater Resting on Permeable Elastic Seabed

2014 ◽  
Vol 716-717 ◽  
pp. 284-288
Author(s):  
Jian Kang Yang ◽  
Hua Huang ◽  
Lin Guo ◽  
Jing Rong Lin ◽  
Qing Yong Zhu ◽  
...  
Keyword(s):  
Shallow Water ◽  
Wave Theory ◽  
Cnoidal Wave ◽  
Load Prediction ◽  
Wave Load ◽  
Seepage Pressure ◽  
Theoretical Investigations ◽  
Nonlinearity Effect ◽  
Wave Nonlinearity ◽  
Wave Induced

Theoretical investigations on cnoidal waves interacting with breakwater resting on permeable elastic seabed are presented in this paper. Based on the shallow water reflected wave theory and Biot consolidation theory on wave-induced seepage pressure, the analytical solutions to first order cnoidal wave reflection and wave-induced seepage pressure are obtained by the eigenfunction expansion approach. Numerical results are presented to show the effects of depth of water, breakwater geometry on cnoidal wave-induced seepage uplift force and overturning moment. Compared with Airy wave theory, in certain shallow water conditions, the shallow water wave theory can more effectively illustrate wave nonlinearity effect in wave load prediction.

Validation and Development of Improved Methods for the Calculation of Wave Loads on XXL Monopiles

2018 ◽  
Author(s):  
Mareike Leimeister ◽  
Bastian Dose
Keyword(s):  
State Of The Art ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Loads ◽  
Wave Load ◽  
Wind Turbine System ◽  
Engineering Models ◽  
Dynamics Simulations ◽  
Diffraction Effects ◽  
Wave Induced

With the offshore wind industry aiming to deploy deeper water sites (> 30 m) while still utilizing monopiles, support structures with larger diameters are required. For the design and assessment of so-called XXL monopiles, wave-induced forces, which become more dominant with increasing diameter, have to be determined accurately. Thus, this study focuses on the identification of differences between state-of-the-art theories for wave load calculations with engineering models and the forces exerted on large monopiles from high-precision numerical reference methods. Within the framework of the research project TANDEM (Towards an Advanced Design of Large Monopiles) a 7 m diameter monopile is designed to support Fraunhofer’s IWT-7.5-164. This offshore wind turbine system is used as reference to determine wave-induced loads based on the MacCamy-Fuchs approach, implemented in models in Modelica. Different waves, defined in a simulation matrix, are investigated to elaborate the significance of diffraction effects, as well as the relevance of non-linear effects. The results are compared to CFD (Computational Fluid Dynamics) simulations. Deviations in the wave-induced forces are analyzed, taking into account the different capabilities of the applied tools, trends in the applicability of the engineering model are elaborated, and suggestions for improvement of the code based on state-of-the-art theories are given.

Wave height distribution in shallow water

1985 ◽  
Vol 12 (4) ◽  
pp. 309-319 ◽  
Author(s):  
T.S. Shahul Hameed ◽  
M. Baba
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Height Distribution ◽  
Wave Height Distribution

Research and Analysis on the Wave Transformation and Irregular Wave Breaking Criterion on the Shore

2016 ◽  
Vol 858 ◽  
pp. 354-358
Author(s):  
Tao You ◽  
Li Ping Zhao ◽  
Zheng Xiao ◽  
Lun Chao Huang ◽  
Xiao Rui Han
Keyword(s):  
Theoretical Model ◽  
Wave Height ◽  
Wave Breaking ◽  
Surf Zone ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Breaking Wave ◽  
Height Distribution ◽  
Flume Experiments ◽  
Irregular Wave

Within the surf zone which is the region extending from the seaward boundary of wave breaking to the limit of wave uprush, breaking waves are the dominant hydrodynamics acting as the key role for sediment transport and beach profile change. Breaking waves exhibit various patterns, principally depending on the incident wave steepness and the beach slope. Based on the equations of conservation of mass, momentum and energy, a theoretical model for wave transformation in and outside the surf zone was obtained, which is used to calculate the wave shoaling, wave set-up and set down and wave height distributions in and outside the surf zone. The analysis and comparison were made about the breaking point location and the wave height variation caused by the wave breaking and the bottom friction, and about the wave breaking criterion under regular and irregular breaking waves. Flume experiments relating to the regular and irregular breaking wave height distribution across the surf zone were conducted to verify the theoretical model. The agreement is good between the theoretical and experimental results.

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