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hydroelastic analysis of a floating bridge under spatially inhomogeneous waves, with emphasis on the effect of drift force modeling

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APPLIED OCEAN RESEARCH 2023年第1期139卷

作者： Li, Shuai Moan, Torgeir Fu, Shixiao Zhang, Shiyuan Xu, Yuwang Shanghai Jiao Tong Univ State Key Lab Ocean Engn Shanghai 200240 Peoples R China Innovat Ctr Adv ship & Deep Sea Explorat Shanghai 200240 Peoples R China Norwegian Univ Sci & Technol Dept Marine Technol NO-7491 Trondheim Norway Ningbo Univ Fac Maritime & Transportat Ningbo Peoples R China

The pontoon-supported floating bridge is an alternative concept for crossing a fjord with a width of up to 5 km. Due to the huge span, the first two natural periods of the bridge are more than 60 s, indicating that the corresponding modes can be excited by slowly-varying drift forces on the pontoons. A simplified approach for determining the drift forces is to assume that the pontoons are independent of the floating bridge, i.e., fixed or freely floating. However, the first-order motions of the pontoons, which are restricted by the deformation of the floating bridge, have a significant effect on the drift forces. To evaluate the uncertainties implied by the simplification of drift forces, in this study, a second-order beam-connected-discrete-modules (BCDM) hydroelastic method is adopted to assess the effect of different drift force models on the floating bridge. In this method, the first-order response amplitude operators (RAOs) of bridge-restricted pontoons are first solved in the frequency-domain. Based on the RAOs, the mean drift forces for each pontoon are then determined by using potential theory. Considering the spatial inhomogeneity of the wave field, the time series of the first-and second-order wave forces are generated by using the linear transfer functions and Newman's approximation, respectively. Then, the method is applied to investigate the hydroelastic responses of a straight side-anchored floating bridge for the crossing site of Bjornafjord. The results show that the horizontal displacement is very sensitive to the different force models implied by various pontoon boundary conditions, i.e., free, fixed, and bridge-restricted. The drift forces on the bridge-restricted pontoons are approximately 10%-20% larger than those for the fixed pontoons. Moreover, wave inhomogeneity results in increased vertical displacements and weak axis bending moments.

关键词： Floating bridge hydroelastic analysis Beam-connected-discrete-modules method Slowly-varying drift force Inhomogeneous wave field Newman's approximation

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hydroelastic analysis OF FLOATING PHOTOVOLTAIC FLOATER UNDER REGULAR WAVES 43

HYDROELASTIC ANALYSIS OF FLOATING PHOTOVOLTAIC FLOATER UNDER...

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ASME 43rd International Conference on Ocean, Offshore and Arctic Engineering (OMAE)

作者： Leventopoulou, Theano Dai, Jian Jiang, Zhiyu Univ Agder Dept Engn Sci N-4879 Grimstad Norway Oslo Metropolitan Univ Dept Built Environm N-0166 Oslo Norway

ISBN: (纸本)9780791887813

The need for renewable energy is increasing and limited land space for installations has led to the rise of floating photovoltaic (FPV) systems, a promising and relatively new technology for harnessing solar power on water surfaces. Apart from the design and the construction of the FPVs, the hydroelastic problem posed by water waves on plate-like floating structures has a considerable value in the offshore application. This study focuses on the frequency-domain hydroelastic analysis of a recently proposed FPV concept with rope connection. In numerical modelling, each FPV float is simplified as a rectangular plate and modelled by using Mindlin plate elements considering only the vertical degrees of freedom. After a mesh convergence study, the FPV systems with one float and two interconnected floats are studied. Through parametric studies considering different wave headings, periods, and connector stiffness, we compare the distributions of displacement, and bending moments along the float for each system. This study serves as a reference for understanding the hydroelasticity effect of simple FPV systems under different environmental conditions and mechanical connections.

关键词： Floating photovoltaic systems Mindlin plate hydroelastic analysis Frequency domain Structural response

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hydroelastic analysis OF SUBMERSIBLE CIRCULAR SEAWEED PLATFORM 42

HYDROELASTIC ANALYSIS OF SUBMERSIBLE CIRCULAR SEAWEED PLATFO...

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ASME 42nd International Conference on Ocean, Offshore and Arctic Engineering (OMAE)

作者： Nguyen, H. P. Wang, C. M. Tullberg, R. Zhang, X. von Herzen, B. Univ Queensland Sch Civil Engn St Lucia Qld 4072 Australia Blue Econ Cooperat Res Ctr Launceston Tas Australia Climate Fdn Stanmore Qld Australia

ISBN: (纸本)9780791886922

This paper presents hydroelastic analysis of a novel submersible circular platform for farming red seaweeds such as Gracilaria dura, Kappahycus alvarezii and Eucheuma. The platform comprises a circular HDPE collar, a system of mooring lines and buoys, and seaweed tube nets. The platform can be submerged during storms to avoid strong surface wave action by filling the collars' compartments with water and be raised to the surface by injecting compressed air into the collars' compartments to displace the water. The platform is modelled by using the software AquaSim, where the collar is modelled by using beam elements, and mooring lines are modelled as truss elements. The wave load acting on the platform is estimated by using the Morison equation. hydroelastic responses of the platform in the floating and submerged modes are investigated. It is found that seaweed tube nets may increase mooring forces significantly and hence the drag forces due to the tube nets cannot be neglected. In addition, by submerging the seaweed platform to an appropriate depth, the deformation of the platform, the von Mises stress and mooring line forces can be reduced considerably as demonstrated herein. Future studies will focus on physical model tests to confirm these findings obtained from numerical simulations.

关键词： seaweed cultivation hydroelastic analysis floating platform submersible platform

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Application of quadratic pressure drop condition in hydroelastic analysis of floating structures protected by perforated barrier

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ENGINEERING analysis WITH BOUNDARY ELEMENTS 2023年第1期157卷 59-70页

作者： Luong, Van Hai Nguyen, H. P. Ho Chi Minh City Univ Technol HCMUT Fac Civil Engn 268 Ly Thuong Kiet St Ho Chi Minh City Vietnam Vietnam Natl Univ Ho Chi Minh City Linh Trung Ward Ho Chi Minh City Vietnam Univ Queensland Sch Civil Engn St Lucia Qld 4072 Australia

This paper presents the application of the quadratic pressure drop condition in hydroelastic analysis of large floating structures protected by perforated barrier. An iterative procedure is proposed to incorporate the quadratic pressure drop condition into the recently developed finite element - dual boundary element method. Numerical examples are carried out to compare the proposed quadratic model with the existing model involving the conventional linear pressure drop condition. It is found that the proposed quadratic model agrees rather well with the linear model for small wave amplitudes. However, for strong waves, there are significant differences between the quadratic model and linear model in terms of the resulting excitation force on the barrier and hydroelastic responses of floating structures. The excitation force from the quadratic model may be up to 100% higher than that from the linear model.

关键词： hydroelastic analysis Floating structure Perforated barrier Quadratic pressure drop condition Dual boundary element method

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hydroelastic analysis of Pontoon-Type Very Large Floating Structures with Multiple Perforated Barrier Attachments

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INTERNATIONAL JOURNAL OF STRUCTURAL STABILITY AND DYNAMICS 2024年第0期

作者： Nguyen, H. P. Nguyen-Thoi, T. Lang Univ Inst Computat Sci & Artificial Intelligence Lab Computat Civil Engn Ho Chi Minh City Vietnam Lang Univ Fac Civil Engn Sch Technol Ho Chi Minh City Vietnam Lang Univ Inst Computat Sci & Artificial Intelligence Lab Appl & Ind Math Ho Chi Minh City Vietnam Lang Univ Fac Mech Elect & Comp Engn Sch Technol Ho Chi Minh City Vietnam

This paper presents a hydroelastic analysis of a pontoon-type Very Large Floating Structure (VLFS) with multiple barriers of varying porosities. The Mindlin plate theory is applied to model the VLFS, while the linear potential wave theory is used to model fluid motions. For interactions between the fluid and impermeable solid surfaces, a boundary condition equating normal fluid and structural velocities is imposed. For fluid interactions with perforated barriers, an empirical model is adopted, where the pressure of fluid passing through the barriers is assumed to drop in a quadratic relationship with the fluid velocity. The mathematical model is solved using an iterative numerical framework based on the finite element method and dual boundary element method. Numerical examples of VLFSs with single and multiple barriers of different porosities are presented. The numerical results indicate that the number and porosity of barrier attachments can be optimized to minimize the hydroelastic responses of the VLFS under specific wave conditions. A combination of a perforated barrier placed in front of an impermeable barrier demonstrates good performance in mitigating the VLFS's hydroelastic responses, with reasonable horizontal forces on the mooring system as compared to other possible combinations of barrier porosities.

关键词： Very Large Floating Structure (VLFS) mitigation method perforated barrier hydroelastic analysis quadratic pressure drop condition dual boundary element method

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A novel coupled finite element method for hydroelastic analysis of FG-CNTRC floating plates under moving loads

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STEEL AND COMPOSITE STRUCTURES 2022年第2期42卷 243-256页

作者： Vu X Nguyen Qui X Lieu Tuan A Le Thao D Nguyen Suzuki, Takayuki Van Hai Luong Ho Chi Minh City Univ Technol HCMUT Fac Civil Engn 268 Ly Thuong Kiet StWard 14Dist 10 Ho Chi Minh City Vietnam Vietnam Natl Univ Ho Chi Minh City VNU HCM Ho Chi Minh City Vietnam Yokohama Natl Univ Dept Civil Engn Hodogaya Ku 79-5 Tokiwadai Yokohama Kanagawa 2408501 Japan

A coupled finite element method (FEM)-boundary element method (BEM) for analyzing the hydroelastic response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) floating plates under moving loads is firstly introduced in this article. For that aim, the plate displacement field is described utilizing a generalized shear deformation theory (GSDT)-based FEM, meanwhile the linear water-wave theory (LWWT)-relied BEM is employed for the fluid hydrodynamic modeling. Both computational domains of the plate and fluid are coincidentally discretized into 4-node Hermite elements. Accordingly, the C1-continuous plate element model can be simply captured owing to the inherent feature of third-order Hermite polynomials. In addition, this model is also completely free from shear correction factors, although the shear deformation effects are still taken into account. While the fluid BEM can easily handle the free surface with a lower computational effort due to its boundary integral performance. Material properties through the plate thickness follow four specific CNT distributions. Outcomes gained by the present FEM-BEM are compared with those of previously released papers including analytical solutions and experimental data to validate its reliability. In addition, the influences of CNT volume fraction, different CNT configurations, water depth, and load speed on the hydroelastic behavior of FG-CNTRC plates are also examined.

关键词： boundary finite element (BEM) finite element method (FEM) functionally graded carbon nanotube-reinforced composite (FG-CNTRC) hydroelastic analysis moving loads

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Second-order sum-frequency hydroelastic analysis of a flexible structure in bichromatic waves

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OCEAN ENGINEERING 2023年第1期269卷

作者： Li, Shuai Fu, Shixiao Zhang, Shiyuan Xu, Yuwang Shanghai Jiao Tong Univ State Key Lab Ocean Engn Shanghai 200240 Peoples R China Collaborat Innovat Ctr Adv Ship & Deep Sea Explora Shanghai 200240 Peoples R China

Due to the complexity of the second-order boundary value problem (BVP) considered in the generalized mode, the second-order hydroelasticity analysis is still challenging. Based on the beam-connected-discrete-modules (BCDM) method, this study proposes a second-order hydroelastic method for floating structures in the frequency domain. In this method, the second-order BVP for flexible structures is replaced by multi-rigid-body hydrodynamics which has been extensively studied. The first-order hydroelastic responses of a hemisphere and the second-order sum-frequency forces using the proposed method are verified against the results obtained by general commercial software and published data. Then, the effect of flexural rigidity on the second-order hydrodynamic forces and responses is investigated. The results show that the second-order forces are dominated by the first-order springing, especially for the quadratic product force component. Additionally, due to the discrete property of the BCDM method for hydrodynamics, the present method can be directly extended to inhomogeneous wave conditions.

关键词： hydroelastic analysis Beam-connected-discrete-modules method Sum-frequency excitation Springing Quadratic transfer function (QTF)

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Finite element-Multi-domain boundary element method for hydroelastic analysis of large floating pontoons with perforated plates

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OCEAN ENGINEERING 2022年 246卷 110659-110659页

作者： Nguyen, H. P. Wang, C. M. Univ Queensland Sch Civil Engn St Lucia Qld 4072 Australia

This paper presents a Finite Element-Multi-Domain Boundary Element (FE-MDBE) method for the hydroelastic analysis of large floating pontoon structures with perforated plates. The structure is modelled by the shell theory while the fluid motion is modelled by using the linear wave theory. When fluid flows through the perforated plates, it is assumed that the velocity is unchanged but the fluid pressure drops by an amount that is determined by an empirical relationship involving the fluid velocity and the porosity of the perforated plate. The equations governing the fluid-structure interaction are solved by using the Finite Element Method (FEM) and Multi-Domain Boundary Element Method (MDBEM). In the MDBEM, the fluid domain is imaginarily decomposed into interior and exterior domains so as to avoid the singularity that arises when using the conventional BEM for solving hydroelastic problems involving thin submerged structures. The proposed FE-MDBE method is verified by comparing its results with experimental results obtained for a flexible platform and a fixed cylinder with perforated sidewall. The verified method is used for the hydrodynamic and hydroelastic analyses of floating breakwaters and large floating platforms with vertical perforated plates at their fore and/or aft.

关键词： Finite element method Multi-domain boundary element method hydroelastic analysis Perforated plates Large floating platform Floating breakwater

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hydroelastic analysis of surface-piercing propeller through one-way and two-way coupling approaches

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART M-JOURNAL OF ENGINEERING FOR THE MARITIME ENVIRONMENT 2019年第3期233卷 844-856页

作者： Javanmardi, Nasrin Ghadimi, Parviz Amirkabir Univ Technol Dept Maritime Engn 424 Hafez Ave Tehran 158754413 Iran

Semi-submerged operation of surface-piercing propellers can cause severe structural stress and deflection due to the high-rate variation of the hydrodynamic loads on each blade in one cycle of revolution. Therefore, a proper hydroelastic analysis regarding these propellers seems imperative. Accordingly, in this article, hydrodynamic performance of a surface-piercing propeller is studied by considering the structural flexibility. The one-way and two-way coupled unsteady Reynolds-averaged Navier-Stokes equations (finite volume method used for the fluid analysis) and direct finite element method (used for the structural analysis) are utilized to analyze an 821-b surface-piercing propeller model. The obtained ventilation patterns and hydrodynamic loads on a single blade of this propeller are compared with the published experimental data. ANSYS multiphysics solvers are used to conduct the targeted simulations. The results are presented for different velocity ratios in the range of [0.8, 1.2] and Froude number Fr = 6.0. The blade maximum deformation and von Mises stress are presented in one cycle of revolution. Based on the obtained results, one may conclude that both the adopted approaches predict the propeller transient hydrodynamic characteristics with good accuracy, compared with the experimental data. However, the two-way approach displays lower maximum structural displacement and stress than one-way simulation. This is attributed to the fact that the two-way approach takes into consideration the added mass and damping effects of the surrounding fluid around the blade.

关键词： Surface-piercing propeller hydroelastic analysis ventilation pattern one-way fluid-structure interaction analysis two-way fluid-structure interaction analysis added mass damping effect

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hydroelastic analysis of surface piercing hydrofoil during initial water entry phase

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SCIENTIA IRANICA 2019年第1期26卷 295-310页

作者： Javanmardi, N. Ghadimi, P. Amirkabir Univ Technol Dept Marine Technol Hales Ave 424POB 15875-4413 Tehran Iran

In the current paper, numerical simulations of Fluid Structure Interaction (FSI) of a SP (Surface Piercing) hydrofoil are conducted in order to study the influence of elasticity on the initial water entry ventilation. Using ANSYS multi physics solvers, two-way FSI analyses are conducted by the implicit coupling of URANS (Unsteady Reynolds Averaged Navier-Stokes) equations with a finite-element method. Numerical results are validated by the well-known rigid and elastic wedge water entry problems. Subsequently, computational results are presented for ranges of different velocity ratios (0.38, 0.64) and elasticity factor [0,4]. Similar to the Surface Piercing Propeller (SPP), performance curves of a wedge water entry are defined. The obtained similar trend of propeller and wedge performance curves in fully ventilated, transition, and partially cavitated operation modes shows that the adopted approach (2D-study) can be appropriate for future related studies. FSI simulation results indicate that structural deformation can highly affect the location of transition point and shift it toward the fully ventilated part at high Froude number and elasticity factor. The overall efficiency loss due to the increase of foil elasticity is observed, and overshoot time of the foil deformation related to the variation of Froude number and elasticity factor is evaluated. (C) 2019 Sharif University of Technology. All rights reserved.

关键词： Surface piercing hydrofoil Oblique water entry hydroelastic analysis Characteristic curves

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