Numerical Simulation and Analysis of Phase-Focused Breaking and Non-Breaking Wave Impact on a Fixed Offshore Platform Deck

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Rameeza Moideen ◽  
Manasa Ranjan Behera ◽  
Arun Kamath ◽  
Hans Bihs
Keyword(s):  
Open Source Software ◽  
Impact Force ◽  
Offshore Structures ◽  
Breaking Wave ◽  
Wave Impact ◽  
Large Wave ◽  
Air Water Interface ◽  
Wave Heights ◽  
Fixed Offshore Platform ◽  
Vertical Impact

Abstract Extreme wave impact due to tsunamis and storm surge create large wave heights that cause destruction to coastal and offshore structures. Focused waves have been used to represent such extreme waves, and in the present study, its impact on offshore deck has been studied numerically. Numerical modeling has been carried out using open-source software reef3d, with the level set method to capture the air–water interface. Focused waves are generated by phase focusing a group of waves at a particular position and time. The nonlinearity of focused waves and its effect on the vertical impact force has been quantified for different airgaps and increasing wave heights. The wave steepness was increased to initiate phase-focused breaking in the numerical wave tank, which was then validated with the experimental results. This breaking-focused wave impact on offshore deck is then studied at different breaking locations. The results for different positionings of the deck with respect to breaker location show that the maximum horizontal impact force on the deck occurs when the plunging crest hits the deck side.

Numerical Simulation and Analysis of Phase Focused Breaking and Non-Breaking Wave Impact on Fixed Offshore Platform Deck

2019 ◽  
Author(s):  
Rameeza Moideen ◽  
Manasa Ranjan Behera ◽  
Arun Kamath ◽  
Hans Bihs
Keyword(s):  
Impact Force ◽  
Experimental Results ◽  
Breaking Wave ◽  
Numerical Wave Tank ◽  
Wave Impact ◽  
Wave Heights ◽  
Numerical Wave ◽  
Focused Wave ◽  
The Impact ◽  
Vertical Impact

Abstract Extreme wave impact due to tsunamis and storm surge create large wave heights causing destruction to coastal and offshore structures. These extreme waves are represented by focused waves in the present study and the impact on offshore deck is studied. Numerical wave tank used is modelled using open-source software REE3D, where the level set method is used to capture the air-water interface. Vertical impact force on offshore deck is computed and compared with the experimental results to validate the numerical model. Focused wave is generated by phase focusing a group of waves at a particular position and time. The nonlinearity of focused wave and its effect on the vertical impact force is quantified for different airgap and increasing wave heights. The steepness of this focused wave is increased to initiate phase focused breaking in the numerical wave tank, which is validated with experimental results of Ghadirian et al., 2016. The main purpose of this paper is to examine breaking focused wave group loads on the offshore deck and to study the impact on deck at different breaking locations. The positioning of the deck with respect to breaker location have shown that the maximum horizontal impact force due to breaking wave occurs when the plunging crest hits the deck side.

scholarly journals Effect of Girder Spacing and Depth on the Solitary Wave Impact on Coastal Bridge Deck for Different Airgaps

2019 ◽  
Vol 7 (5) ◽  
pp. 140 ◽  
Author(s):  
Rameeza Moideen ◽  
Manasa Ranjan Behera ◽  
Arun Kamath ◽  
Hans Bihs
Keyword(s):  
Solitary Wave ◽  
Bridge Deck ◽  
Impact Force ◽  
Storm Surges ◽  
Wave Impact ◽  
Wave Condition ◽  
Bridge Damage ◽  
Wave Heights ◽  
The Impact ◽  
Vertical Impact

Coastal bridge damage has become a severe issue of concern in the recent past with the destruction of a considerable number of bridges under the impact of waves during tsunami and storm surges. These events have become more frequent, with waves reaching the bridge deck and causing upliftment and destruction. Past studies have demonstrated the establishment of various theoretical equations which works well for the submerged deck and regular wave types but show much scatter and uncertainty in case of a deck that is above still water level (SWL). The present study aims to generate a solitary wave to represent an extreme wave condition like a tsunami in the numerical wave tank modeled using the open source computational fluid dynamics (CFD) model REEF3D and to study the vertical impact force on the coastal bridge deck. A parametric study is carried out for increasing wave heights, girders spacing and depth for varying airgaps to analyze the effect of these parameters on the peak vertical impact force. It is observed that increasing the girder spacing and girder depth is effective in reducing the peak vertical impact force for the cases considered.

An Evaluation of Wave Impact Indicators

2009 ◽  
Author(s):  
Zhigang Tian
Keyword(s):  
Wave Breaking ◽  
Offshore Structures ◽  
Phase Method ◽  
Impact Loads ◽  
Wave Steepness ◽  
Wave Load ◽  
Wave Impact ◽  
Large Wave ◽  
Impact Indicators ◽  
Local Wave

Wave impact on offshore structures has been the focus of several studies, due to its significant effect on offshore operations. We evaluate several parameters (wave impact indicators) which can be adopted to indicate the possibility of wave impact on offshore structures due to extreme waves. The indicators can be estimated quickly with given sea states, and thus may provide useful information to offshore structure designers at early design phases. Definitions of three wave impact indicators are presented and discussed. The first indicator, Ψ, is proposed by Stansberg (2008). The second one considered is a wave breaking parameter, μ, originally presented by Song and Banner (2002) in their construction of a wave breaking criterion. Finally, we propose a more generalized impact indicator, βn. The subscript n indicates its dependence on local wave steepness. Our study demonstrates that the three indicators are analytically related. To evaluate these indicators numerically, 2nd order random surface waves are generated with random phase method and Two-Dimensional Fast Fourier Transform (2D FFT). Hilbert analysis of the wave signal reveals that all indicators are able to identify steep and energetic waves that may potentially cause large wave impact loads. Further numerical study demonstrates that the quantitative correlation of wave impact loads to μ is less promising than that to Ψ and βn; while βn provides the best relationship to both local wave impact load and global wave load with its dependence on local wave steepness adjusted (i.e. adjusting n). The correlation is independent of sea states. Estimations and recommendations for thresholds of the two impact indicators (i.e. Ψ and βn with n = 1) are made based on model test results. With proper estimation of the thresholds, both indicators can be applied to predict wave impact and wave impact probability in given sea states.

Numerical Modeling of Breaking Wave Kinematics and Wave Impact Pressures on a Vertical Slender Cylinder

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arntsen
Keyword(s):  
Free Surface ◽  
Breaking Waves ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Breaking Wave ◽  
Total Force ◽  
Wave Loads ◽  
Wave Impact ◽  
Large Wave ◽  
Surface Deformations

Wave loads from breaking waves on offshore wind turbine (OWT) substructures in shallow waters still remain uncertain. The interaction of breaking waves with structures is characterized by complex free surface deformations, instantaneous impact of the water mass against the structure, and consequently large wave forces on the structures. The main objective of the paper is to investigate wave impact pressures and kinematics during the interaction of breaking waves with a vertical cylinder using the open-source computational fluid dynamics (CFD) model REEF3D. The model is based on the Reynolds-averaged Navier–Stokes (RANS) equations coupled with the level set method and k–ω turbulence model. Three wave impact conditions are considered in this study. The numerically simulated free surface deformations around the cylinder during the breaking wave interaction are also presented for different wave impact conditions. For three wave impact conditions, the wave impact pressure and the horizontal and vertical components of the particle velocity are computed in front of the cylinder and analyzed. The pressure and velocity profile at their maximum values are also examined and discussed. In addition, the total force is calculated for three breaking conditions and they are correlated with the pressure and kinematics during the interaction.

A Wave Impact Parameter

2008 ◽  
Author(s):  
Carl Trygve Stansberg
Keyword(s):  
Impact Parameter ◽  
Hilbert Transform ◽  
Offshore Structures ◽  
Model Tests ◽  
Large Majority ◽  
Random Wave ◽  
Critical Events ◽  
Wave Impact ◽  
Wave Heights ◽  
Wave Trains

Critical events in random wave trains that can lead to impact on offshore structures are addressed. Experience from model testing has shown that impact is correlated with steep and energetic waves, characterized by high crests, wave heights, orbital velocities, slope, or a combination of all. A new impact alert parameter derived directly from a wave record, unifying these properties in a physically consistent way, is proposed. Hilbert transform analysis is applied. The analysis is demonstrated through application on numerical and laboratory wave records. Impact responses from model tests with floating offshore structures in steep storm sea states are compared to predictions made by the new simple alert parameter derived from the calibrated wave records. It is found that a large majority of events identified by the new parameter turn out to be real critical events also in the response records.

Theoretical and Experimental Analysis of Air Gap Response and Wave-on-Deck Impact of Floating Offshore Structures

2007 ◽  
Author(s):  
Saeid Kazemi ◽  
Atilla Incecik
Keyword(s):  
Experimental Analysis ◽  
Impact Force ◽  
Offshore Structures ◽  
Air Gap ◽  
Wave Impact ◽  
Impact Prediction ◽  
Impact Forces ◽  
Wave Elevation ◽  
Local Wave ◽  
Air Gap Responses

A comparative study between the theoretical and experimental analysis of air gap response and potential wave-on-deck impact forces of floating offshore structures is the main topic of this study. Both motion of the platform and the local wave elevation are important in air gap responses and wave impact forces. So, accurate and efficient computational analysis of wave induced loads and resulting platform’s responses and wave elevation is important in the prediction of air gap and evaluation of possible wave impact force. Numerical modelling for air gap and wave impact prediction is particularly complicated in the case of floating offshore structures because of their large volume, and the resulting effects of wave diffraction and radiation. Therefore, for new floating platforms, the model tests are often performed as part of their design process. The overall aim of this study is to introduce a simplified numerical method with sufficient accuracy suitable for preliminary design stages of a floating offshore platform to predict the air gap response using hybrid method and to evaluate the vertical wave impact force using Wagner-based method. The results obtained from the proposed method have been compared with those obtained from the experiments carried out in the wave tank of the Newcastle University.

scholarly journals Preliminary Evaluation of the Effectiveness of Using Artificial Reefs to Reduce Breaking Wave Impact on Offshore Structures

2017 ◽  
Author(s):  
Charlotte Loedsen Andersen ◽  
Ida Skov Milthers ◽  
Julie Caroee Kristoffersen ◽  
Christos Thomas Georgakis ◽  
Longbin Tao
Keyword(s):  
Artificial Reef ◽  
Breaking Waves ◽  
Offshore Structures ◽  
Artificial Reefs ◽  
Breaking Wave ◽  
Preliminary Evaluation ◽  
Offshore Platforms ◽  
Wave Impact ◽  
Maximum Displacement ◽  
The People

Waves breaking on offshore platforms can have damaging consequences for the structure and for the safety of the people working on it. Recent unexpected extreme wave events have shown the effects that breaking waves have on offshore platforms. In this paper, the results from a scaled experimental investigation conducted the Newcastle University wind, wave and current tank, are presented. With these tests, the effectiveness of using artificial reefs to avoid or lessen the effects of breaking wave activity is examined. Four different types of artificial reefs are tested and their effects are compared to a reference test with no artificial reef. The comparison is based on the changes of the size and location of the maximum wave amplitude, the maximum displacement of a scaled platform and the artificial reef’s ability to dissipate wave energy. Overall, the results show that placing the rectangular reef in the tank produces the most promising results. However, it is also shown that placing any one of the artificial reefs in the tank will affect a change in the wave motion. Thus, this investigation shows that the use of an artificial reef could be a step in securing a higher level of protection for personnel and operations.

Computation of Wave Impact Pressures and Kinematics During Plunging Breaking Wave Interaction With a Vertical Cylinder Using CFD Modelling

2017 ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arntsen
Keyword(s):  
Free Surface ◽  
Vertical Cylinder ◽  
Wave Interaction ◽  
Breaking Waves ◽  
Offshore Wind Turbine ◽  
Breaking Wave ◽  
Total Force ◽  
Wave Impact ◽  
Large Wave ◽  
Surface Deformations

Wave loads from breaking waves on offshore wind turbine (OWT) substructures in shallow waters still remain uncertain. The interaction of breaking waves with structures is characterized by complex free surface deformations, instantaneous impact of the water mass against the structure and consequently large wave forces on the structures. The main objective of the paper is to investigate wave impact pressures and kinematics during the interaction of breaking waves with a vertical cylinder using the open-source CFD model REEF3D. The model is based on the Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the level set method (LSM) and k-ω turbulence model. Three wave impact conditions are considered in the present study. The numerically simulated free surface deformations around the cylinder during the breaking wave interaction are also presented for different wave impact conditions. For three wave impact conditions, the wave impact pressure and the horizontal and vertical components of the particle velocity are computed in front of the cylinder and analyzed. The pressure and velocity profile at their maximum values are also examined and discussed. In addition, the total force is calculated for three breaking conditions and they are correlated with the pressure and kinematics during the interaction.

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