Numerical Simulation of Wave in Deck Loading on Offshore Structures

2014 ◽  
Author(s):  
Yu Chen ◽  
Yanling Wu ◽  
Graham Stewart ◽  
Johan Gullman-Strand ◽  
Xin Lu
Keyword(s):  
Free Surface ◽  
Research Programme ◽  
Offshore Structures ◽  
Navier Stokes ◽  
Impact Loads ◽  
Extreme Waves ◽  
Extreme Wave ◽  
Existing Structures ◽  
The Impact ◽  
The Waves

Extreme wave impacts on the decks of offshore structures with insufficient air gap may cause damage or even collapse with safety, economic, and pollution consequences. In this study, the impact loads on a fixed platform deck have been predicted numerically by employing a Navier-Stokes solver with the free-surface captured by the volume of fluid (VOF) method. 3D numerical simulations of wave-deck interactions for long-crested extreme waves were performed. The simulations successfully captured the evolution of impact loads and free surface of the waves during the interaction with the platform deck. A detailed parametric analysis of wave-deck interactions showed significant differences in loads under various situations and confirmed the large magnitudes of the loads to be expected during impact. The results presented include a solid box and a more realistic case of under-deck beams. These provide a useful benchmark for predicting wave loadings on platform decks and through this research programme the longer term aim is to establish improved guidelines for assessing the risk of existing structures.

Wave Impact Loads on the Bottom of Flat Decks

2021 ◽  
Author(s):  
Daniel de Oliveira Costa ◽  
Julia Araújo Perim ◽  
Bruno Guedes Camargo ◽  
Joel Sena Sales Junior ◽  
Antonio Carlos Fernandes ◽  
...  
Keyword(s):  
Scale Effects ◽  
Offshore Structures ◽  
Model Tests ◽  
Analytical Models ◽  
Navier Stokes ◽  
Impact Loads ◽  
Wave Impact ◽  
Wave Channel ◽  
Waves And Currents ◽  
The Impact

Abstract Slamming events due to wave impact on the underside of decks might lead to severe and potentially harmful local and/or global loads in offshore structures. The strong nonlinearities during the impact require a robust method for accessing the loads and hinder the use of analytical models. The use of computation fluid dynamics (CFD) is an interesting alternative to estimate the impact loads, but validation through experimental data is still essential. The present work focuses on a flat-bottomed model fixed over the mean free surface level submitted to regular incoming waves. The proposal is to reproduce previous studies through CFD and model tests in a different reduced scale to provide extra validation and to identify possible non-potential scale effects such as air compressibility. Numerical simulations are performed in both experiments’ scales. The numerical analysis is performed with a marine dedicated flow solver, FINE™/Marine from NUMECA, which features an unsteady Reynolds-averaged Navier-Stokes (URANS) solver and a finite volume method to build spatial discretization. The multiphase flow is represented through the Volume of Fluid (VOF) method for incompressible and nonmiscible fluids. The new model tests were performed at the wave channel of the Laboratory of Waves and Currents (LOC/COPPE – UFRJ), at the Federal University of Rio de Janeiro.

scholarly journals Numerical modelling of extreme waves by Smoothed Particle Hydrodynamics

2011 ◽  
Vol 11 (2) ◽  
pp. 419-429 ◽  
Author(s):  
M. H. Dao ◽  
H. Xu ◽  
E. S. Chan ◽  
P. Tkalich
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Rogue Waves ◽  
Offshore Structures ◽  
Wave Crest ◽  
Extreme Waves ◽  
Coastal Structures ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
The Impact ◽  
The Waves

Abstract. The impact of extreme/rogue waves can lead to serious damage of vessels as well as marine and coastal structures. Such extreme waves in deep water are characterized by steep wave fronts and an energetic wave crest. The process of wave breaking is highly complex and, apart from the general knowledge that impact loadings are highly impulsive, the dynamics of the breaking and impact are still poorly understood. Using an advanced numerical method, the Smoothed Particle Hydrodynamics enhanced with parallel computing is able to reproduce well the extreme waves and their breaking process. Once the waves and their breaking process are modelled successfully, the dynamics of the breaking and the characteristics of their impact on offshore structures could be studied. The computational methodology and numerical results are presented in this paper.

scholarly journals EXTREME WAVE PRESSURES AND LOADS ON A PILE-SUPPORTED WHARF DECK - INFLUENCES OF AIR GAP AND WAVE DIRECTION

2018 ◽  
pp. 5
Author(s):  
Andrew Cornett
Keyword(s):  
Offshore Structures ◽  
Model Tests ◽  
Scale Model ◽  
Extreme Waves ◽  
Wave Direction ◽  
Coastal Structures ◽  
Extreme Wave ◽  
Wave Impact ◽  
The Past ◽  
Water Depths

Many deck-on-pile structures are located in shallow water depths at elevations low enough to be inundated by large waves during intense storms or tsunami. Many researchers have studied wave-in-deck loads over the past decade using a variety of theoretical, experimental, and numerical methods. Wave-in-deck loads on various pile supported coastal structures such as jetties, piers, wharves and bridges have been studied by Tirindelli et al. (2003), Cuomo et al. (2007, 2009), Murali et al. (2009), and Meng et al. (2010). All these authors analyzed data from scale model tests to investigate the pressures and loads on beam and deck elements subject to wave impact under various conditions. Wavein- deck loads on fixed offshore structures have been studied by Murray et al. (1997), Finnigan et al. (1997), Bea et al. (1999, 2001), Baarholm et al. (2004, 2009), and Raaij et al. (2007). These authors have studied both simplified and realistic deck structures using a mixture of theoretical analysis and model tests. Other researchers, including Kendon et al. (2010), Schellin et al. (2009), Lande et al. (2011) and Wemmenhove et al. (2011) have demonstrated that various CFD methods can be used to simulate the interaction of extreme waves with both simple and more realistic deck structures, and predict wave-in-deck pressures and loads.

scholarly journals Loads on a Point-Absorber Wave Energy Converter in Regular and Focused Extreme Wave Events

2020 ◽  
Author(s):  
Eirini Katsidoniotaki ◽  
Edward Ransley ◽  
Scott Brown ◽  
Johannes Palm ◽  
Jens Engström ◽  
...  
Keyword(s):  
Wave Energy ◽  
Wave Train ◽  
Offshore Structures ◽  
Wave Energy Converter ◽  
Extreme Waves ◽  
Extreme Wave ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Extreme Loads

Abstract Accurate modeling and prediction of extreme loads for survivability is of crucial importance if wave energy is to become commercially viable. The fundamental differences in scale and dynamics from traditional offshore structures, as well as the fact that wave energy has not converged around one or a few technologies, implies that it is still an open question how the extreme loads should be modeled. In recent years, several methods to model wave energy converters in extreme waves have been developed, but it is not yet clear how the different methods compare. The purpose of this work is the comparison of two widely used approaches when studying the response of a point-absorber wave energy converter in extreme waves, using the open-source CFD software OpenFOAM. The equivalent design-waves are generated both as equivalent regular waves and as focused waves defined using NewWave theory. Our results show that the different extreme wave modeling methods produce different dynamics and extreme forces acting on the system. It is concluded that for the investigation of point-absorber response in extreme wave conditions, the wave train dynamics and the motion history of the buoy are of high importance for the resulting buoy response and mooring forces.

Extreme Load-Response Mechanisms of a Tension Leg Platform due to Larger Wave Crests: Some Results of the ‘CresT’ JIP

2011 ◽  
Author(s):  
Janou Hennig ◽  
Jule Scharnke ◽  
Bas Buchner ◽  
Joris van den Berg
Keyword(s):  
Gulf Of Mexico ◽  
Extreme Event ◽  
Offshore Structures ◽  
Wave Load ◽  
Extreme Wave ◽  
Response Process ◽  
Load Response ◽  
Extreme Load ◽  
The Waves ◽  
Crest Height

For the design of ships and offshore structures the largest crest height which can be expected in their lifetime is of key importance. This was confirmed by several incidences e.g. in hurricanes in the Gulf of Mexico during the recent years. This is why MARIN started up the CresT JIP with a number of partners. The CresT JIP is now completed and some results of the extreme wave load and response mechanisms observed during model tests with a TLP will be presented in this paper. First an overview is given of the loading and response process during the most extreme event observed. As a next step the loading and response is related to the time and spatial characteristics of the waves, as it is not per definition the highest local crest or wave height that results in the most extreme dynamic response. Furthermore, the effect of different TLP design variations and short-crestedness will be discussed.

Wave-in-Deck Load on a Jacket Platform, CFD Calculations Compared With Experiments

2014 ◽  
Author(s):  
Bogdan Iwanowski ◽  
Tone Vestbøstad ◽  
Marc Lefranc
Keyword(s):  
Free Surface ◽  
Industrial Application ◽  
Computational Models ◽  
Cfd Simulation ◽  
Navier Stokes ◽  
Extreme Wave ◽  
Navier Stokes Equation ◽  
Jacket Platform ◽  
Irregular Wave ◽  
Start Up

The paper presents an industrial application of CFD for calculation of Wave-In-Deck load due to an extreme wave. Particular attention is given to flow kinematics initialization that is necessary to start up a CFD simulation. The applied CFD code, ComFLOW, is a Navier-Stokes equation solver with an improved Volume of Fluid (iVOF) method employed to displace and re-construct fluids free surface. For incoming waves high enough for a negative air-gap and therefore with Wave-In-Deck loads, a jacket platform was tested in model basin, for both regular and irregular wave cases. One of goals of these model tests was verification of CFD codes. The experimental and computational models of the structure are exactly the same. In the paper, the measured Wave-In-Deck forces are compared with CFD results.

scholarly journals Simulation of free-surface flow in a tank using the Navier-Stokes model and unstructured finite volume method

2005 ◽  
Vol 219 (3) ◽  
pp. 251-266 ◽  
Author(s):  
X Zhang ◽  
N M Sudharsan ◽  
R Ajaykumar ◽  
K Kumar
Keyword(s):  
Free Surface ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Free Surface Flow ◽  
Offshore Structures ◽  
Surface Flow ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Volume Method ◽  
Unstructured Finite Volume Method

Modelling free-surface flow has very important applications in many engineering areas such as oil transportation and offshore structures. Current research focuses on the modelling of free surface flow in a tank by solving the Navier-Stokes equation. An unstructured finite volume method is used to discretize the governing equations. The free surface is tracked by dynamically adapting the mesh and making it always surface conforming. A mesh-smoothing scheme based on the spring analogy is also implemented to ensure mesh quality throughout the computaiton. Studies are performed on the sloshing response of a liquid in an elastic container subjected to various excitation frequencies. Further investigations are also carried out on the critical frequency that leads to large deformation of the tank walls. Another numerical simulation involves the free-surface flow past as submerged obstacle placed in the tank to show the flow separation and vortices. All these cases demonstrate the capability of this numerical method in modelling complicated practical problems.

scholarly journals AN EXPERIMENTAL STUDY OF EXTREME WAVE KINEMATICS ON OPPOSING DEPTH-VARYING CURRENTS

2018 ◽  
pp. 37
Author(s):  
Xuyang Niu ◽  
Yuxiang Ma ◽  
Xiaozhou Ma ◽  
Guohai Dong ◽  
Yongbo Song
Keyword(s):  
Experimental Studies ◽  
Oceanic Circulation ◽  
Extreme Waves ◽  
Extreme Wave ◽  
Wind Force ◽  
Wave Kinematics ◽  
The Past ◽  
Key Factor ◽  
Generation Mechanisms ◽  
The Waves

In the past decades, there are numerous reports on the accidents caused by extremely large waves. A large number of papers have contributed to the study on the physical properties and the generation mechanisms of such large waves. However, most of the research has been carried out without presence of currents. In the real ocean, the waves most likely coexist with currents. In many circumstances, owing to wind force and oceanic circulation, the currents are commonly not uniform and vary with depth, which plays an important role in the evolution of gravity waves (Swan et al., 2001). Wave kinematics is a key factor in designing structures. However, experimental studies of the influence of depth-varying currents on extreme waves are mainly considered for the changing of spatial and temporal geometric characteristics (Yao and Wu, 2006). In the present study, the kinematics of extreme waves on opposing depth-varying currents will be investigated using the PIV technology.

On the Distribution of Wave Impact Loads on Offshore Structures

2017 ◽  
Author(s):  
Thomas B. Johannessen ◽  
Øystein Lande ◽  
Øistein Hagen
Keyword(s):  
Model Test ◽  
Load Distribution ◽  
Impact Load ◽  
Peak Load ◽  
Offshore Structures ◽  
Impact Loads ◽  
Test Results ◽  
Wave Impact ◽  
The Impact ◽  
Crest Height

For offshore structures in harsh environments, horizontal wave impact loads should be taken into account in design. Shafts on GBS structures, and columns on semisubmersibles and TLPs are exposed to impact loads. Furthermore, if the crest height exceeds the available freeboard, the deck may also be exposed to wave impact loads. Horizontal loads due to waves impacting on the structure are difficult to quantify. The loads are highly intermittent, difficult to reproduce in model tests, have a very short duration and can be very large. It is difficult to calculate these loads accurately and the statistical challenges associated with estimating a value with a prescribed annual probability of occurrence are formidable. Although the accurate calculation of crest elevation in front of the structure is a significant challenge, industry has considerable experience in handling this problem and the analysis results are usually in good agreement with model test results. The present paper presents a statistical model for the distribution of horizontal slamming pressures conditional on the incident crest height upwave of the structure. The impact load distribution is found empirically from a large database of model test results where the wave impact load was measured simultaneously at a large number of panels together with the incident crest elevation. The model test was carried out on a circular surface piercing column using long simulations of longcrested, irregular waves with a variety of seastate parameters. By analyzing the physics of the process and using the measured crest elevation and the seastate parameters, the impact load distribution model is made seastate independent. The impact model separates the wave impact problem in three parts: – Given an incident crest in a specified seastate, calculate the probability of the crest giving a wave impact load above a threshold. – Given a wave impact event above a threshold, calculate the distribution of the resulting peak load. – Given a peak load, calculate the distribution of slamming pressures at one spatial location. The development of the statistical model is described and it is shown that the model is appropriate for fixed and floating structures and for wave impact with both columns and the deck box.

Extreme Wave Amplification And Impact Loads On Offshore Structures

2005 ◽  
Author(s):  
C.T. Stansberg ◽  
R. Baarholm ◽  
T. Kristiansen ◽  
E.W.M. Hansen ◽  
G. Rortveit
Keyword(s):  
Offshore Structures ◽  
Impact Loads ◽  
Extreme Wave ◽  
Wave Amplification
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