Fundamental Study for Human Dynamic Responses to the Motion of Fishing Vessels in Ocean Waves

Abstract Ocean waves are one of the sustainable resources of renewable energy for carbon-free electricity. For cost-effective commercial-scale projects, Wave Energy Converters (WECs) are deployed in arrays with optimum spacing as an alternative for a large (oscillatory) device in isolation. It has been found that when the wave excitation frequency is close to the resonant frequency of the WEC, the efficiency factor of energy farms, called q-factor, increases with the oscillation amplitude of the device. It has been found that the maximum absorbed energy of WECs depends directly on array configuration as that the radiated and incident wave fields interfere to direct the energy flux in the ocean towards the floating bodies. In this paper, the fully nonlinear interaction between two 3D floating bodies in close proximity and excited near its’ resonance is studied using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH). Apart from the calculations of q factor, hydrodynamic forces acting on the floating bodies and their dynamic responses are also calculated. An optimum array of WECs is proposed.

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Effects of Fish Nets on the Nonlinear Dynamic Performance of a Floating Offshore Wind Turbine Integrated with a Steel Fish Farming Cage

International Journal of Structural Stability and Dynamics ◽

10.1142/s021945542050042x ◽

2020 ◽

Vol 20 (03) ◽

pp. 2050042 ◽

Cited By ~ 2

Author(s):

Y. Lei ◽

S. X. Zhao ◽

X. Y. Zheng ◽

W. Li

Keyword(s):

Wind Turbine ◽

Nonlinear Dynamic ◽

Dynamic Performance ◽

Fish Farming ◽

Ocean Waves ◽

Dynamic Responses ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Floating Offshore Wind Turbine ◽

Wind Sea

This paper aims to study the effects of fish nets on the nonlinear dynamic performance of a floating offshore wind turbine integrated with a steel fish farming cage (FOWT-SFFC). Fully coupled aero-hydro-servo-elastic numerical models of FOWT-SFFC, with and without nets, are constructed to probe the nonlinear time-domain stochastic response. The first-order potential flow model with quadratic drag forces is employed to calculate the hydrodynamic loading on the foundation. The effects of nets on the damping ratios of 6 degree-of-freedom motions and on their displacement response amplitude operators (RAOs) are respectively investigated in numerical decay tests and monochromatic regular waves. The results show that the nets help to increase the damping level for the whole system and reduce motion RAOs when wave periods are around the natural periods of motions, while nets play insignificant role in motions when wave periods are far away from motion natural periods. The dynamic performances of FOWT-SFFC with and without nets under random ocean waves, the combined random wind and random waves as well as current are comprehensively compared and discussed. The simulation results indicate that in wind-sea dominated conditions, the nets tend to slightly increase the dynamic responses of FOWT-SFFC, especially the components corresponding to natural periods. Nonetheless, under sea states that comprise both wind-sea waves and swell, nets help to reduce the dynamic responses of FOWT-SFFC by introducing additional damping.

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Dynamic Response Analysis of Harbor Caisson Structure Under Various Boundary Conditions

Volume 2: Structures, Safety and Reliability ◽

10.1115/omae2009-79294 ◽

2009 ◽

Author(s):

Jeong-Tae Kim ◽

So-Young Lee ◽

Dong-Soo Hong ◽

Jin-Hak Yi ◽

Yoon-Koo Kang

Keyword(s):

Boundary Conditions ◽

Frequency Response ◽

Experimental Tests ◽

Element Model ◽

Dynamic Responses ◽

Scale Model ◽

Small Scale ◽

Response Analysis ◽

Fundamental Study ◽

Various Boundary Conditions

In this study, vibration responses of harbor caisson structures with various boundary conditions are experimentally examined as a fundamental study to develop a health assessment technique for harbor structures. To achieve the objective, four-step approach is implemented. Firstly, a target caisson structure is selected and a small-scale model of the caisson model is constructed in the laboratory. Secondly, a finite element model of the caisson model is generated to analyze dynamic responses of the structure. Thirdly, experimental tests are performed on the caisson model to obtain dynamic responses under various boundary conditions and impact locations. Four different boundary conditions, 1) ‘hanging by crane’, 2) ‘standing on styrofoam block’, 3) ‘standing on sand mat’, and 4) ‘standing on concrete floor’ are considered. Finally, variation of frequency response ratio assurance criterion and correlation coefficients of frequency response functions are analyzed.

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Analytical Solution for Static and Dynamic Analysis of Graphene-Based Hybrid Flexoelectric Nanostructures

Journal of Composites Science ◽

10.3390/jcs5030074 ◽

2021 ◽

Vol 5 (3) ◽

pp. 74

Author(s):

Kishor Balasaheb Shingare ◽

Susmita Naskar

Keyword(s):

Lead Zirconate Titanate ◽

Volume Fraction ◽

Plate Theory ◽

Closed Form Solution ◽

Dynamic Responses ◽

Mode Shapes ◽

Piezoelectric Composite ◽

Fundamental Study ◽

Static And Dynamic Analysis ◽

Flexoelectric Effect

Owing to their applications in devices such as in electromechanical sensors, actuators and nanogenerators, the consideration of size-dependent properties in the electromechanical response of composites is of great importance. In this study, a closed-form solution based on the linear piezoelectricity, Kirchhoff’s plate theory and Navier’s solution was developed, to envisage the electromechanical behaviors of hybrid graphene-reinforced piezoelectric composite (GRPC) plates, considering the flexoelectric effect. The governing equations and respective boundary conditions were obtained, using Hamilton’s variational principle for achieving static deflection and resonant frequency. Moreover, the different parameters considering aspect ratio, thickness of plate, different loadings (inline, point, uniformly distributed load (UDL), uniformly varying load (UVL)), the combination of different volume fraction of graphene and piezoelectric lead zirconate titanate are considered to attain the desired bending deflection and frequency response of GRPC. Different mode shapes and flexoelectric coefficients are also considered and the results reveal that the proper addition of graphene percentage and flexoelectric effect on the static and dynamic responses of GRPC plate is substantial. The obtained results expose that the flexoelectric effect on the piezoelastic response of the bending of nanocomposite plates are worth paying attention to, in order to develop a nanoelectromechanical system (NEMS). Our fundamental study sheds the possibility of evolving lightweight and high-performance NEMS applications over the existing piezoelectric materials.

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Wave and wave-current actions on a bridge tower: An experimental study

Advances in Structural Engineering ◽

10.1177/1369433218816523 ◽

2018 ◽

Vol 22 (6) ◽

pp. 1467-1478 ◽

Cited By ~ 2

Author(s):

Chengxun Wei ◽

Daocheng Zhou ◽

Jinping Ou

Keyword(s):

Pile Group ◽

Ocean Waves ◽

Experimental Results ◽

Dynamic Responses ◽

Wave Forces ◽

Base Shear ◽

Shear Forces ◽

Natural Period ◽

Motion Responses ◽

Bridge Tower

With a scale of 1:100, an experimental model was set up to investigate the dynamic responses of a bridge tower subjected to ocean waves and wave-currents. The bridge tower was designed for a sea-crossing bridge. Based on a pile-group foundation, it was designed to be a typical gate-type structure. Wave-induced base shear forces on the foundation and motion responses of the tower were measured and analyzed. The experimental results show that when a wave period is close to the natural period of the structure, an obvious resonance will be induced on the structure. For different wave action angles, the longitudinal incident waves induced the largest longitudinal base shear forces on the foundation and the greatest dynamic motions on the upper tower of the structure. Because of the pile-group effectiveness, the incident directions of the waves and the wave periods affect the acting forces on the foundation of the structure. For wave-current actions, forward currents increase the forward wave forces on the foundation and decrease the backward forces, but do not significantly affect the motion responses of the upper tower. The experimental results can be used as the verification data for numerical calculations. With the structural forms of the pile-group and the gate-type tower being typical, the results given in this study can be used as a reference for similar engineering designs.

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Integration of Wave Energy Harnessing Technologies to the Needs of Coastal Societies in North Carolina

Volume 1: Fuels, Combustion, and Material Handling; Combustion Turbines Combined Cycles; Boilers and Heat Recovery Steam Generators; Virtual Plant and Cyber-Physical Systems; Plant Development and Construction; Renewable Energy Systems ◽

10.1115/power2018-7389 ◽

2018 ◽

Author(s):

Akshith Subramanian ◽

Gagee Raut ◽

Navid Goudarzi

Keyword(s):

North Carolina ◽

Wave Energy ◽

Reference Model ◽

Ocean Waves ◽

The Body ◽

Department Of Energy ◽

Dynamic Responses ◽

Stable Form ◽

Energy Potential ◽

Wave Data

Wave Energy is a predictable and stable form of renewable energies. In this work, the wave energy potential along the North Carolina shore is calculated using six-year (2012–2017) National Buoy Database (NDBC). The wave data from two buoys (US 192 and US 430) were collected and the average significant wave height (HS) and corresponding time period (T) were determined. The Reference Model 3 (RM3) defined by Department of Energy (DOE) was used to explore the potential power generation from wave energy. Simulations were setup on WEC-Sim, an open-source code based on MATLAB developed by the DOE. A six-degree of freedom solver was used to obtain the results for heave and pitch forces for the float. Dynamic responses were calculated by solving equations of motion based on Cummins’ equation about the body center of gravity. Waves were modeled as irregular ocean waves using North Carolina shore wave data. The preliminary results obtained the heave and surge forces on RM3 and the body reaction forces. The results from this work can be used for determination of RM3 performance for NC shore.

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Dynamic Responses of a Multilayered Transversely Isotropic Poroelastic Seabed Subjected to Ocean Waves and Currents

Journal of Marine Science and Engineering ◽

10.3390/jmse10010073 ◽

2022 ◽

Vol 10 (1) ◽

pp. 73

Author(s):

Xi Chen ◽

Qi Zhang ◽

Xiang Yuan Zheng ◽

Yu Lei

Keyword(s):

Young’S Modulus ◽

Young's Modulus ◽

Dynamic Stiffness ◽

Transversely Isotropic ◽

Ocean Waves ◽

Offshore Structures ◽

Dynamic Responses ◽

Vertical Shear ◽

Waves And Currents ◽

Poroelastic Seabed

In this study, a semi-analytical solution to the dynamic responses of a multilayered transversely isotropic poroelastic seabed under combined wave and current loadings is proposed based on the dynamic stiffness matrix method. This solution is first analytically validated with a single-layered and a two-layered isotropic seabed and then verified against previous experimental results. After that, parametric studies are carried out to probe the effects of the soil’s anisotropic characteristics and the effects of ocean waves and currents on the dynamic responses and the maximum liquefaction depth. The results show that the dynamic responses of a transversely isotropic seabed are more sensitive to the ratio of the soil’s vertical Young’s modulus to horizontal Young’s modulus (Ev/Eh) and the ratio of the vertical shear modulus to Ev (Gv/Ev) than to the vertical-to-horizontal ratio of the permeability coefficient (Kv/Kh). A lower degree of quasi-saturation, higher porosity, a shorter wave period, and a following current all result in a greater maximum liquefaction depth. Moreover, it is revealed that the maximum liquefaction depth of a transversely isotropic seabed would be underestimated under the isotropic assumption. Furthermore, unlike the behavior of an isotropic seabed, the transversely isotropic seabed tends to liquefy when fully saturated in nonlinear waves. This result supplements and reinforces the conclusions determined in previous studies. This work affirms that it is necessary for offshore engineering to consider the transversely isotropic characteristics of the seabed for bottom-fixed and subsea offshore structures.

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