Application of Breather Solutions for the Investigation of Wave/Structure Interaction in High Steep Waves

2012 ◽  
Author(s):  
Günther F. Clauss ◽  
Marco Klein ◽  
Matthias Dudek ◽  
Miguel Onorato
Keyword(s):  
Real World ◽  
Wave Structure ◽  
Model Tests ◽  
Design Stage ◽  
Regular Waves ◽  
Freak Waves ◽  
Structure Interaction ◽  
Steep Waves ◽  
The Impact ◽  
Wave Structure Interaction

During the design process of floating structures, different specifications have to be aligned such as the range of application, the warranty of economical efficiency as well as the reliability and are an inevitable integral part of the evaluation process during the design stage. The validation of the performance by means of model tests in terms of sea state behavior and the associated local and global structural loads are an important milestone within this process. Therefore it is necessary to determine an adequate test procedure which covers all essential areas of interest. Thereby one field of interest are limiting criteria of the design such as maximum local and global loads as well as maximum accelerations due to the impact of extraordinarily high waves, at which the floating structure has to survive. Different alternatives are available to conduct model tests in high, steep waves — transient wave packages, regular waves, irregular waves with random phases or more sophisticated deterministic tailored irregular wave sequences such as reproductions from numerical simulations and real-world measurements. This paper introduces a new approach for the systematic investigation of wave/structure interaction in high, steep waves. Exact solutions of the nonlinear Schrodinger equation — the so called breather solutions — are implemented for the generation of extraordinarily high waves. Three types of breather solutions are investigated in the seakeeping basin and to cover the full range of interest, each solution has been used to generate freak waves at certain frequencies. To evaluate the applicability of breather solutions for model tests two types of ships — a LNG Carrier and a Chemical Tanker — are investigated in the seakeeping basin. The ships are segmented and connected with strain gauges to detect the vertical wave bending moment. Furthermore, green water probes are installed on deck to evaluate the local impact on the bow of the freak waves. The obtained results are compared to investigations in regular waves with certain frequency and steepness as well as in real-world freak wave reproductions.

Application of an Absorbing Boundary Condition in a Wave-Structure Interaction Problem

2012 ◽  
Author(s):  
Bulent Duz ◽  
Rene H. M. Huijsmans ◽  
Mart J. A. Borsboom ◽  
Peter R. Wellens ◽  
Arthur E. P. Veldman
Keyword(s):  
Boundary Condition ◽  
Traditional Approach ◽  
Wave Structure ◽  
Offshore Structures ◽  
Absorbing Boundary Condition ◽  
Design Stage ◽  
Absorbing Boundary ◽  
Structure Interaction ◽  
Interaction Problem ◽  
Wave Structure Interaction

For the design of offshore structures, an accurate assessment of the ability of the structure to survive in extreme sea conditions is of prime importance. Next to scaled model tests on the structure in waves, also CFD capabilities are at the disposal of the designer. However even with the fastest computers available, it is still a challenge to use CFD in the design stage because of the large computational resources they require. In this study we focus our attention on the implementation of an absorbing boundary condition (ABC) in a wave-structure interaction problem. Unlike the traditional approach where the boundaries are located far from the object to avoid reflection, we gradually locate them closer while at the same time observing the influence of the absorbing boundary condition on the solution. Numerical calculations are performed using the CFD simulation tool ComFLOW which is a volume-of-fluid (VOF) based Navier-Stokes solver. Comparisons with experimental results are also provided and the performance of the ABC is discussed.

Modelling of Wave-Structure Interaction of a Cylinder in Regular Sea Waves With Vessel Motions Using Coupled Transient CFD and Diffraction Methodology

2015 ◽  
Author(s):  
David Jia ◽  
Paul Schofield ◽  
Joanne Shen ◽  
Jim Malachowski
Keyword(s):  
Steady State ◽  
Hollow Cylinder ◽  
Cfd Simulation ◽  
Traditional Approach ◽  
Wave Structure ◽  
Sea Waves ◽  
Regular Waves ◽  
Structure Interaction ◽  
Added Masses ◽  
Wave Structure Interaction

This paper is a continuation of our previous paper [1] (OMAE2014-23225) where we did a parametric study for wave-structure interaction of a hollow cylinder in regular sea waves without vessel motions. The effect of waves and current on the motion of the cylinder and the associated forces were evaluated using a state-of-the-art methodology [2] (OMAE2013-11569) for predicting the motions and loads of subsea equipment and structures during offshore operations. In this paper, we extend the solution to include wave – structure interaction in regular sea waves and vessel motions. The 5th order Stokes regular waves in CFD and vessel motions are included in the modeling. This methodology couples the transient CFD with a hydrodynamic motion analysis after diffraction analyses, instead of relying on the traditional approach which uses simplified equations or empirical formulae to estimate hydrodynamic coefficients [3], or using steady-state CFD simulation on stationary equipment and structures to predict drag and added masses on submerged structures. The time domain diffraction simulation is coupled with a multiphase CFD simulation of subsea equipment and structures in waves. A transient CFD model with rigid body motions for the equipment and structures calculates added masses, forces and moments on the equipment and structures for the diffraction analysis, while the diffraction analysis calculates linear and angular velocities for the CFD simulation. In this paper, simulations are performed to investigate effect of the vessel motions on the motion of a hollow cylinder in regular sea waves. The results are compared with that from the traditional approach. This coupled methodology has potential applications in analyses of the motions of subsea equipment and structures in waves during offshore operations. The results in this paper show wave-structure interaction of a hollow cylinder in regular sea waves, and the effect of vessel motions on the motion of the cylinder. The results provide better understanding of structure motion in regular waves with vessel motions using this coupled methodology. The coupled methodology eliminates the inaccuracy inherited from assumed or calculated hydrodynamic properties that are obtained by using simplified equations or empirical formulations, or by using steady-state CFD analyses in traditional decoupled approaches. The results show that the coupled physics of regular sea waves, vessel motions and cylinder motion is captured by using this methodology. The coupled physics is not captured by the traditional approach.

scholarly journals Investigation of a Stochastic Inverse Method to Estimate an External Force: Applications to a Wave-Structure Interaction

2012 ◽  
Vol 2012 ◽  
pp. 1-25 ◽  
Author(s):  
S. L. Han ◽  
Takeshi Kinoshita
Keyword(s):  
External Force ◽  
Inverse Method ◽  
Inverse Function ◽  
Wave Structure ◽  
Dynamic Responses ◽  
Structure Interaction ◽  
External Forces ◽  
Interaction Problem ◽  
Wave Structure Interaction

The determination of an external force is a very important task for the purpose of control, monitoring, and analysis of damages on structural system. This paper studies a stochastic inverse method that can be used for determining external forces acting on a nonlinear vibrating system. For the purpose of estimation, a stochastic inverse function is formulated to link an unknown external force to an observable quantity. The external force is then estimated from measurements of dynamic responses through the formulated stochastic inverse model. The applicability of the proposed method was verified with numerical examples and laboratory tests concerning the wave-structure interaction problem. The results showed that the proposed method is reliable to estimate the external force acting on a nonlinear system.

scholarly journals Efficient Solution of the 3D Laplace Problem for Nonlinear Wave-Structure Interaction

2008 ◽  
Author(s):  
Harry B. Bingham ◽  
Allan P. Engsig-Karup
Keyword(s):  
Nonlinear Wave ◽  
Efficient Solution ◽  
Wave Structure ◽  
Finite Difference Schemes ◽  
Surface Boundary ◽  
Computational Domain ◽  
Problem Size ◽  
Structure Interaction ◽  
Nonlinear Wave Structure ◽  
Wave Structure Interaction

This contribution presents our recent progress on developing an efficient solution for fully nonlinear wave-structure interaction. The approach is to solve directly the three-dimensional (3D) potential flow problem. The time evolution of the wave field is captured by integrating the free-surface boundary conditions using a fourth-order Runge-Kutta scheme. A coordinate-transformation is employed to obtain a time-constant spatial computational domain which is discretized using arbitrary-order finite difference schemes on a grid with one stretching in each coordinate direction. The resultant linear system of equations is solved by the GMRES iterative method, preconditioned using a multigrid solution to the linearized, lowest-order version of the matrix. The computational effort and required memory use are shown to scale linearly with increasing problem size (total number of grid points). Preliminary examples of nonlinear wave interaction with variable bottom bathymetry and simple bottom mounted structures are given.

scholarly journals Wave–structure interaction in hybrid wave farms

2018 ◽  
Vol 83 ◽  
pp. 386-412 ◽  
Author(s):  
Siming Zheng ◽  
Yongliang Zhang ◽  
Gregorio Iglesias
Keyword(s):  
Wave Structure ◽  
Hybrid Wave ◽  
Structure Interaction ◽  
Wave Structure Interaction

Practical Structural Assessment of Offshore Structures for Wave Slap

2012 ◽  
Author(s):  
Joong Soo Moon ◽  
Tae Hyun Park ◽  
Woo Seung Sim ◽  
Hyun Soo Shin
Keyword(s):  
Static Pressure ◽  
Impact Load ◽  
Offshore Structures ◽  
Model Tests ◽  
Design Stage ◽  
Load Prediction ◽  
Structural Assessment ◽  
Pressure Impulse ◽  
The Impact ◽  
Design Pressure

By the combination of theoretical and empirical approach, the methodology for practical structural assessment of offshore structures for wave slap is proposed. It is developed for engineers in the sense that the precise design pressure is easily obtainable and quickly applicable in early and detail design stage. For impact load prediction, the Pressure-Impulse theory that was well developed and validated in coastal engineering field is applied. The impact pressures are classified into three types (traditional, sharp, and immersed slap) according to model tests and BP Schiehallion FPSO’s bow monitoring. The time histories of impact pressures for the classified impact types are generated with the pressure impulse predicted by the Pressure-Impulse theory. Nonlinear transient structural analyses are performed using the time series of impact pressures to obtain equivalent static pressure factors. Finally, the design pressure is determined by multiplying the maximum peak pressure by the equivalent static pressure factor. The results are validated through the comparison with model tests and dedicated reports.

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