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.

Wave-in-Deck Loads for an Intricate Pile-Supported Pier and Variation With Deck Clearance

2013 ◽  
Author(s):  
Andrew Cornett ◽  
David Anglin ◽  
Trevor Elliott
Keyword(s):  
Water Waves ◽  
Three Dimensional ◽  
Wave Structure ◽  
Physical Modelling ◽  
Interaction Process ◽  
Air Gap ◽  
Scale Model ◽  
Shallow Water Waves ◽  
Structure Interaction ◽  
Wave Structure Interaction

Many deck structures are located at elevations low enough to be impacted by large waves. However, due to the highly complex and impulsive nature of the interactions between wave crests and intricate deck structures, establishing reliable estimates of extreme pressures and forces for use in design remains challenging. In this paper, results from an extensive set of three-dimensional scale model tests conducted to support the design of a large pile-supported pier (or jetty) are presented and discussed. Relationships between maximum wave-in-deck loads and the deck clearance (air gap) are presented and discussed. Results from numerical simulations of the wave-structure interaction process obtained using the three-dimensional CFD software FLOW-3D® are also presented and discussed. Finally, some initial comparisons between the numerical and physical modelling are also included. This paper provides new insights concerning the character and magnitude of the hydrodynamic pressures and loads exerted on intricate pile-supported deck structures due to impact by non-linear shallow-water waves, and the relationships between the hydrodynamic forcing and the deck clearance or air gap.

Response Behaviour of Perforated Cylinders in Regular Waves

2011 ◽  
Author(s):  
Srinivasan Chandrasekaran ◽  
S. Parameswara Pandian
Keyword(s):  
Outer Cylinder ◽  
Wave Structure ◽  
Offshore Structures ◽  
Experimental Investigations ◽  
Coastal Protection ◽  
Wave Loads ◽  
Wave Impact ◽  
Protection Measures ◽  
Cylindrical Structures ◽  
Perforated Cylinder

In order to reduce the direct wave impact, coastal and offshore structures are often constructed with one or more perforated layers. Several permeable breakwaters and docks have been deployed in coastal protection measures to reduce direct impact due to encountered wave loads and to reduce wave reflection in front of these structures as well; compared with the traditional ones, such structural forms are found to be more economical. Such structures result in lesser surface fluctuation in harbours due to the low reflection, which is vital for loading and unloading of ships. Deploying permeable breakwaters posses other advantages namely: i) increasing water circulation; ii) retaining water quality and iii) enhances coastal protection. Emerged and submerged perforated cylindrical structures reduce wave-structure interactions and scouring problems considerably, but their use on floating structures is scarce in the literature. This study is focused on detailed experimental investigations carried out on impermeable inner cylinder encompassed by a larger outer cylinder with perforatios along its length. By varying the porosity and perforatio diameter, their influence on the hydrodynamic response of the cylindrical member is highlighted through the current study. The conclusions on the comparison of forces in the cylinder with and without perforated cylinder coverage are presented.

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.

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.

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.

Experimental Investigation on the Dynamic Response of a Three Legged Articulated Type Offshore Wind Tower

2016 ◽  
Author(s):  
Chinsu Mereena Joy ◽  
Anitha Joseph ◽  
Lalu Mangal
Keyword(s):  
Dynamic Response ◽  
Wind Turbine ◽  
Renewable Energy Sources ◽  
Offshore Structures ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Experimental Investigations ◽  
Offshore Wind Turbine ◽  
Ocean Engineering ◽  
Study Results

Demand for renewable energy sources is rapidly increasing since they are able to replace depleting fossil fuels and their capacity to act as a carbon neutral energy source. A substantial amount of such clean, renewable and reliable energy potential exists in offshore winds. The major engineering challenge in establishing an offshore wind energy facility is the design of a reliable and financially viable offshore support for the wind turbine tower. An economically feasible support for an offshore wind turbine is a compliant platform since it moves with wave forces and offer less resistance to them. Amongst the several compliant type offshore structures, articulated type is an innovative one. It is flexibly linked to the seafloor and can move along with the waves and restoring is achieved by large buoyancy force. This study focuses on the experimental investigations on the dynamic response of a three-legged articulated structure supporting a 5MW wind turbine. The experimental investigations are done on a 1: 60 scaled model in a 4m wide wave flume at the Department of Ocean Engineering, Indian Institute of Technology, Madras. The tests were conducted for regular waves of various wave periods and wave heights and for various orientations of the platform. The dynamic responses are presented in the form of Response Amplitude Operators (RAO). The study results revealed that the proposed articulated structure is technically feasible in supporting an offshore wind turbine because the natural frequencies are away from ocean wave frequencies and the RAOs obtained are relatively small.

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
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