Wave-Body Interactions Among an Array of Truncated Vertical Cylinders

2016 ◽  
Author(s):  
Qian Zhong ◽  
Ronald W. Yeung
Keyword(s):  
Velocity Potential ◽  
Wave Radiation ◽  
Fast Computation ◽  
Array Configuration ◽  
Point Absorber ◽  
Exciting Forces ◽  
Wave Exciting Forces ◽  
Matched Eigenfunction Expansions ◽  
Wave Farm ◽  
Vertical Cylinders

A semi-analytical method is developed to investigate water-wave radiation and diffraction by an array of truncated vertical cylinders as a model for a point-absorber wave farm. Each cylinder can have independent movements in six modes. The method of matched eigenfunction expansions is applied to obtain the velocity potential for the fluid. To achieve fast computation, the effects of evanescent modes of locally scattered waves from one cylinder are neglected in the near fields of the neighboring cylinders. Wave-exciting forces and moments on an individual cylinder or a group of cylinders, situated among an array, are evaluated by a new, generalized form of Haskind relation that is applicable to an array configuration. In results, hydrodynamic coefficients and wave-exciting loads are presented for arrays of different configurations. Comparisons between wave-exciting loads obtained from the generalized Haskind relation and those from direct diffraction solutions show excellent agreements.

On the Radiation and Diffraction of Surface Waves by Submerged Spheroids

1989 ◽  
Vol 33 (02) ◽  
pp. 84-92
Author(s):  
G. X. Wu ◽  
R. Eatock Taylor
Keyword(s):  
Degrees Of Freedom ◽  
Velocity Potential ◽  
Three Dimensional ◽  
Added Mass ◽  
Wave Radiation ◽  
Legendre Functions ◽  
Incoming Wave ◽  
Six Degrees Of Freedom ◽  
Damping Coefficients ◽  
Exciting Forces

The problem of wave radiation and diffraction by submerged spheroids is analyzed using linearized three-dimensional potential-flow theory. The solution is obtained by expanding the velocity potential into a series of Legendre functions in a spheroidal coordinate system. Tabulated and graphical results are provided for added mass and damping coefficients of various spheroids undergoing motions in six degrees of freedom. Graphs are also provided for exciting forces and moments corresponding to a range of incoming wave angles.

Forward-Speed Vertical Wave Exciting Forces on Ships

1985 ◽  
Vol 29 (02) ◽  
pp. 105-111
Author(s):  
P. D. Sclavounos
Keyword(s):  
Velocity Potential ◽  
Reverse Flow ◽  
Diffraction Problem ◽  
Three Dimensional ◽  
Forward Speed ◽  
Direct Solution ◽  
Radiation Problem ◽  
Strip Theory ◽  
Exciting Forces ◽  
Wave Exciting Forces

Expressions are derived for the heave and pitch exciting force and moment on a ship advancing in waves. They are obtained in the form of an integral over the ship axis of the outer source strength of the reverse-flow radiation problem multiplied by the value of the incident-wave velocity potential. Their performance is tested for two slender spheroids. Comparisons are made with predictions obtained from a three-dimensional numerical solution at zero speed—the expression common to strip-theory programs which uses the ship hull as the integration surface—and the direct solution of the diffraction problem.

scholarly journals Wave forces on three-dimensional floating bodies with small forward speed

1991 ◽  
Vol 227 ◽  
pp. 135-160 ◽  
Author(s):  
Jan Nossen ◽  
John Grue ◽  
Enok Palm
Keyword(s):  
Velocity Potential ◽  
The Body ◽  
Wave Forces ◽  
Forward Speed ◽  
Floating Bodies ◽  
Wave Drift ◽  
Exciting Forces ◽  
Wave Exciting Forces ◽  
Wave Drift Damping ◽  
The Mean

A boundary-integral method is developed for computing first-order and mean second-order wave forces on floating bodies with small forward speed in three dimensions. The method is based on applying Green's theorem and linearizing the Green function and velocity potential in the forward speed. The velocity potential on the wetted body surface is then given as the solution of two sets of integral equations with unknowns only on the body. The equations contain no water-line integral, and the free-surface integral decays rapidly. The Timman-Newman symmetry relations for the added mass and damping coefficients are extended to the case when the double-body flow around the body is included in the free-surface condition. The linear wave exciting forces are found both by pressure integration and by a generalized far-field form of the Haskind relations. The mean drift force is found by far-field analysis. All the derivations are made for an arbitrary wave heading. A boundary-element program utilizing the new method has been developed. Numerical results and convergence tests are presented for several body geometries. It is found that the wave exciting forces and the mean drift forces are most influenced by a small forward speed. Values of the wave drift damping coefficient are computed. It is found that interference phenomena may lead to negative wave drift damping for bodies of complicated shape.

An Analytical Solution of Wave Exciting Loads on CALM Buoy with Skirt

2013 ◽  
Vol 477-478 ◽  
pp. 254-258 ◽  
Author(s):  
Dong Jiao Wang ◽  
Shi Peng Sun
Keyword(s):  
Analytical Solution ◽  
Decomposition Method ◽  
Domain Decomposition Method ◽  
Wave Theory ◽  
Finite Depth ◽  
Validation Process ◽  
Exciting Forces ◽  
Wave Exciting Forces ◽  
Matched Eigenfunction Expansions ◽  
Truncated Cylinder

Linearized potential wave theory is applied to calculate the wave exciting loads on a CALM buoy in water of finite depth. The solution is based on the domain decomposition method and the unknown constants in the velocity potentials are determined by matched eigenfunction expansions. A comparison of the analytical solution with published experimental results on a vertical truncated cylinder is performed as part of the validation process. The effects of the disk on the wave exciting forces are discussed.

Theory of Short Wave Excitation

1986 ◽  
Vol 30 (03) ◽  
pp. 147-152
Author(s):  
Yong Kwun Chung
Keyword(s):  
Incident Wave ◽  
Characteristic Length ◽  
Finite Depth ◽  
Short Wave ◽  
The Body ◽  
Wave Number ◽  
Floating Body ◽  
Wave Excitation ◽  
Exciting Forces ◽  
Wave Exciting Forces

When the wavelength of the incident wave is short, the total surface potential on a floating body is found to be 2∅ i & O (m-l∅ i) on the lit surface and O (m-l∅ j) on the shadow surface where ~b i is the potential of the incident wave and m the wave number in water of finite depth. The present approximation for wave exciting forces and moments is reasonably good up to X/L ∅ 1 where h is the wavelength and L the characteristic length of the body.

scholarly journals Wave Exciting Forces on Groups of Floating Bodies

1979 ◽  
Vol 1979 (145) ◽  
pp. 79-87 ◽  
Author(s):  
Akira Masumoto ◽  
Yoshio Yamagami ◽  
Ryuji Sakata
Keyword(s):  
Floating Bodies ◽  
Exciting Forces ◽  
Wave Exciting Forces

scholarly journals Enhancement of a 3-DOF submerged wave energy device using bistability

2020 ◽  
Vol 3 (2) ◽  
pp. 73-82
Author(s):  
Benjamin Schubert ◽  
William S. P. Robertson ◽  
Benjamin S. Cazzolato
Keyword(s):  
Wave Energy ◽  
Degrees Of Freedom ◽  
Phase Relationship ◽  
Bistable System ◽  
Viscous Drag ◽  
Regular Waves ◽  
Point Absorber ◽  
Exciting Forces ◽  
Bistable Mechanism ◽  
The Impact

The dynamic response of a submerged CETO shaped quasi-point absorbing wave energy converter coupled to a bistable power take off is presented in this study. Whilst the impact of bistability has been shown in a limited number of situations to improve the amount of power generated, many models have been restricted to a single degree of freedom and often ignore drag effects. To overcome these model limitations, a submerged single tether point absorber with a bistable power take off was modelled using both 1 and 3 degrees of freedom. The device was subjected to regular waves and included a simple model of viscous drag. The bistable mechanism was provided by a magnetic dipole model quantified by a dimensionless parameter applicable to any bistable system. The performance of the device was is assessed by the theoretical power generated. Over each model, the previously observed benefit of bistability was not consistently obtained. Simulations of regular waves demonstrated an increase in generated power for suboptimal conditions for some frequencies, while a reduction in generated power was observed in optimal conditions. The performance increase showed strong correlation to the phase relationship between the motion and exciting forces as a result of bistability.

scholarly journals Ocean Wave-Structure Interaction of Two Wave Energy Converters in Malaysian Water

2018 ◽  
Vol 203 ◽  
pp. 01010
Author(s):  
Ng ChengYee ◽  
Tuhaijan Siti Nor Adha ◽  
Velluruzhathil John Kurian ◽  
Lim Wai Loon
Keyword(s):  
Renewable Energy ◽  
Wave Energy ◽  
Wave Structure ◽  
Separation Distance ◽  
Ocean Wave ◽  
Mooring Lines ◽  
Rapid Urbanization ◽  
Array Configuration ◽  
Point Absorber ◽  
Heave Motion

Due to rapid urbanization and industrialization, the consumption of electricity in the world is expected to increase, thus leads to the fast development of the renewable energy industry. In 2016, 24.5% of the electricity is produced by renewable energy. There are several types of renewable energy, e.g. solar, wind, and ocean wave. The ocean wave energy is identified to have the greatest potential for electricity generation. There are various types of wave energy converter (WEC) that have been designed for harnessing the wave energy, e.g. the oscillating water column, salter duck, point absorber, water dagon etc. Due to the smaller dimension, the point absorber is the most suitable WEC to be deployed in an array configuration, whereby each isolated WEC interacts and alters the vicinity of the wave formation by absorbing, radiating, and diffracting the wave. Subsequently, the wave interference will also affect the WEC’s performance. The objective of the present study is to investigate the optimum separation distance, d, that would resulting to an optimum performance between two WECs in an array configuration using a computational fluid dynamics (CFD) software. The analysis considered an isolated WEC and two WECs, i.e. the heaving point absorbers with three point catenary mooring lines. The influence of the separation distance towards diffraction and response amplitude operator (RAO) of an array of two WECs was evaluated. The optimum production of the wave energy by the heaving point absorber is observed to be highly dependant on the relative heave motion of the two WECs [1]. In the present study, it shows that the optimum distance between two WECs in an array configuration is 20 m, whereby the maximum heave RAO were identified.

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