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.

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.

Numerical and Experimental Investigation of Wave-Structure Interactions on Coastal Highways and Levees

2012 ◽  
Author(s):  
Ning Zhang ◽  
Zhuang Li ◽  
Alan Davis ◽  
Puxuan Li ◽  
Anpeng He
Keyword(s):  
Gulf Coast ◽  
Wave Structure ◽  
Storm Surges ◽  
Pressure Data ◽  
Coastal Structures ◽  
Structure Interaction ◽  
Frequency Components ◽  
Simulation Results ◽  
Interaction Problem ◽  
Wave Structure Interaction

Erosion due to storm surges and wave actions damages coastal highway and levee systems in Gulf coast. During previous hurricanes, a large portion of coastal highways were damaged by the storm surge. The damages are often on the downstream shoulder of the highways. In this study, numerical and experimental analyses were conducted to uncover the erosion-causing flow physics, which aims to improve the erosion-resistant design of coastal structures. The impacts of wave actions, especially frequency components, on the coastal structures were investigated. A test levee was built, and was placed on a Gulf beach for experiment. Real time wave action pressure data on the surface of the test levee were collected and analyzed. The frequency components of the pressure data agree with numerical simulation results. Numerically, FLUENT was used to simulate this wave-structure interaction problem.

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.

A New Coupled Model for the Assessment of Offshore Structures in Non-Gaussian Seas

2020 ◽  
Author(s):  
Griet Decorte ◽  
Alessandro Toffoli ◽  
Geert Lombaert ◽  
Jaak Monbaliu
Keyword(s):  
Coupled Model ◽  
Wave Interaction ◽  
Wave Structure ◽  
Offshore Structures ◽  
Higher Order ◽  
Structure Interaction ◽  
Cfd Models ◽  
Non Gaussian ◽  
Wave Structure Interaction ◽  
Interaction Phenomena

Abstract Although wave-wave interaction phenomena in random seas have shown to lead to a departure from Gaussian statistics and therefore to a higher occurrence of extreme waves, they are usually not taken along in the assessment of the dynamic behaviour of offshore structures. Supported by a rapid increase of computational resources, the use of Computational Fluid Dynamics (CFD) models has become viable for studying the above mentioned wave-structure interaction phenomena. Still, these models remain computationally expensive, which impedes their use for the large domains and the long periods of time necessary for studying non-Gaussian seas. Therefore, a one-way domain decomposition strategy is proposed, which takes advantage of the recent advances in CFD as well as of the computational benefits of the higher-order spectral (HOS) models previously used to assess non-Gaussian seas. The unidirectional non-Gaussian sea obtained by this coupled HOS-CFD model shows excellent agreement with the target wave field generated by the higher-order spectral numerical wave tank. In addition, the wave-structure interaction for a simplified monopile, which is excited by a non-Gaussian sea, seems to be captured well.

Experimental Investigation of Dynamic Response of Tension Leg Platform With Perforated Members

2013 ◽  
Author(s):  
Vishruth Srinath ◽  
Srinivasan Chandrasekaran
Keyword(s):  
Dynamic Response ◽  
Wave Structure ◽  
Offshore Structures ◽  
Scale Model ◽  
Experimental Investigations ◽  
Cylindrical Structures ◽  
Structure Interaction ◽  
Near Shore ◽  
Outer Cover ◽  
Wave Structure Interaction

Perforated cylindrical structures are extensively used in near-shore breakwaters to reduce wave-structure interaction and scouring; however use of perforated members on floating offshore structures is not widespread. Current study investigates the influence of perforated members on the dynamic response of Tension Leg Platforms (TLP) through model testing. Detailed experimental investigations are carried out on the scale model of TLP with and without porous outer cover, under unidirectional regular waves. Based on studies conducted, it is shown that fluid-structure interaction is reduced in the presence of outer perforated covers; as a result, surge and pitch responses decrease.

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