15:30
Fluid structural inter-actions III
Chair: Rene Huijsmans
15:30
30 mins
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HYDROELASTICITY OF A VLFS IN NON-UNIFORM INCIDENT WAVES
Jun Ding, Chao Tian, Yousheng Wu, Zhiwei Li, Zhen Lu, Xiaofeng Wu
Abstract: For the very large floating structure (VLFS) which is deployed near coasts, islands and reefs, the encounter wave conditions will become extremely complex. Therefore, the traditional methods with uniform wave inputs cannot be applied to the hydroelastic analysis of VLFS near coasts, islands and reefs. The actual wave condition in different modules, i.e. the non-uniform incident waves should be considered. Taking into account the effect of non-uniform incident waves, a new analysis procedure THAFTS-NUIW is developed based on the classical three-dimensional hydroelasticity theory. The motion and connector loads of VLFS in the non-uniform regular and irregular waves are studied. Compared with the results calculated by traditional method, significant differences can be found in the hydroelastic results. The theory and results presented in the paper provide a technical foundation for the load determination and structure design of VLFS (including connectors) near coasts, islands and reefs.
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16:00
30 mins
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NUMERICAL ANALYSIS OF HYDROELASTIC EFFECT ON SHIP STRUCTURAL RESPONSE
George Jagite, Xiang-Dong Xu, Xiao-Bo Chen, Sime Malenica
Abstract: In the last years very large floating structures (VLFS) are continuous appearing in the waters of developed coastal cities under different layouts like floating airports, floating bridges, floating storage facilities, mobile offshore structures and even for habitation. Their size is growing up rapidly and the structure become more and more flexible and prone to wave induced vibrations. In case of relatively “soft” floating bodies the springing phenomenon can appear and it represents a steady state dynamic response produced at the resonance case associated with first few structural natural frequencies excited by wave actions. For large floating structures using the classical rigid body seakeeping analysis and modelling the hydro-structure interface by the transfer of the pressure is not sufficient and hydroelastic coupling is necessary to solve the interaction between the surface waves and the rigid-elastic body. This paper is concerned with the importance of analysing the influence of hydroelastic vibratory response on structural fatigue damage for VLFS. The hydro-structure analysis was performed using HOMER software by coupling 3D potential flow code for hydrodynamics and 3D FEM structural model of a very large floating structure [1]. The modal superposition method is used, which means that the total structural response is presented as a series of eigenvalue structural modes pre-calculated by the 3D-FEM structural software. By defining additional boundary value problems for radiation potential associated with dry structural modes the coupling with hydrodynamics model is performed. By resolving the interaction between the surface waves and the floating elastic body the hydroelastic response is obtained. Top-down technique [2] was used to determine the influence of the hydroelastic effect called springing on structural fatigue damage of several fatigue details. In order to clearly evaluate the influence of springing on the overall ship structural response the total structural response is decomposed into quasi-static and dynamic part.
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