Hydrodynamic modelling of a direct drive wave energy converter

An improved method of hydrodynamic pressure calculation for circular hollow piers in deep water under earthquake

Based on the methods of variable separation and matching eigenfunction expansion for the velocity potential, an analytical solution is developed for a wave diffraction problem on a submerged vertical cylinder in finite water depth. It is validated by comparison with the results from a higher-order boundary-element method and convergent examinations on the number of expanding models. Numerical examinations are carried out to investigate the influences of submerged depth, cylinder length, and water depth. The wave forces on the submerged cylinder are decreased with the increase of submerged depth. Compared with a floated cylinder, the surge force is always small, whereas the heave force and pitch moment may be larger than those on the floated cylinder at some frequencies. The influence of the cylinder length is also analyzed for surge, heave, and pitch results.

Analytical Solution of a Wave Diffraction Problem on a Submerged Cylinder

In this paper, diffraction problem of a floating vertical circular cylinder is studied. Detailed analytical solution for the boundary value problem to evaluate the wave loads for the cylinder with heave and pitch motions in water of finite depth in the presence of an incident wave, has been presented. Accordingly, diffraction problem for a truncated vertical circular cylinder of radius in water of finite depth has been considered. Incident wave used in this problem, is assumed to be linear with amplitude . In order to calculate the added mass and damping coefficients of the pitch motion of the body, strip theory is applied. For the heave motion, the hydrodynamic coefficients are found by the submerged disk method. Parametric studies of the effects of the wave excitation force on the floating cylinder have been performed for two different cases: 1) constant draft of the cylinder with varying water depth and 2) varying draft of the cylinder with constant water depth.

https://eprints.ncl.ac.uk/file_store/production/249838/29FCEEAA-BAD7-4C38-9CD3-EA040C7EE668.pdf

Determination of the Heave and Pitch Motions of a Floating Cylinder by Analytical Solution of its Diffraction Problem and Examination of the Effects of Geometric Parameters on its Dynamics in Regular Waves

Hydrodynamic properties of two vertical truncated cylinders in waves

On diffraction and radiation problem for a cylinder over a caisson in water of finite depth

A buoy as an offshore structure is often placed over a convex such as a caisson or a submerged island. The hydrodynamic fluid/solid interaction becomes more complex due to the convex compared with that on the flat. Both the buoy and the convex are idealized as vertical cylinders. Linear potential theory is used to investigate the response amplitude and the hydrodynamic force for a buoy over a convex due to diffraction and radiation in water of finite depth. These are derived from the total velocity potential. A set of theoretical added mass, damping coefficient, and exciting force expressions have been proposed. Analytical results of the response amplitude and hydrodynamic force are given. Finally, the numerical results show that the effect of the convex on the response amplitude and hydrodynamic force for the buoy is ignored if the size of the convex is relatively smaller.

Response Amplitude and Hydrodynamic Force for a Buoy over a Convex

The invention provides a floating waver power generating device with double floating bodies, comprising a big floating body floating on the sea surface, which is linked to the sea bottom by anchor chain, and on which sliding way is set; small floating body set on the big floating body, which can slide along the sliding way. The upper end of small floating body is connected to the chain and the chain is winded on the chain wheel. The chain wheel is connected with hydraulic and power generating system in the big floating body by clutch. The invention mainly makes use of the relative movement of big and small floating bodies under the waver effect to distill waver energy. The invention can exist in sea as a single body and also exist in sea with multiple devices connected with each other so as to realize the demand of developing oceanic wave energy at a large scale. Because the oceanic wave energy exists in nature and permanently, once the invention device is used, power can be outputted continuously. Compared with common power generating method with exhaust source, the invention has huge developing advantage.

Floating type double-floater ocean wave power generator

The scattering of linear water waves by an infinitely long rectangular structure parallel to a vertical wall in oblique seas is investigated. Analytical expressions for the diffracted potentials are derived using the method of separation of variables. The unknown coefficients in the expressions are determined through the application of the eigenfunction expansion matching method. The expressions for wave forces on the structure are given. The calculated results are compared with those obtained by the boundary element method. In addition, the influences of the wall, the angle of wave incidence, the width of the structure, and the distance between the structure and the wall on wave forces are discussed. The method presented here can be easily extended to the study of the diffraction of obliquely incident waves by multiple rectangular structures.

Scattering of Linear Water Waves by a Fixed and Infinitely Long Rectangular Structure Parallel to a Vertical Wall in Oblique Seas

A new analytical method is proposed to analyze the force acting on a rectangular oscillating buoy due to linear waves. In the method a new analytical expression for the diffraction velocity potential is obtained first by use of the eigenfunction expansion method and then the wave excitation force is calculated by use of the known incident wave potential and the diffraction potential. Compared with the classical analytical method, it can be seen that the present method is simpler for a two-dimensional problem due to the comparable effort needed for the computation of diffraction potential and for that of radiated potential. To verify the correctness of the method, a classical example in the reference is recomputed and the obtained results are in good accordance with those by use of other methods, which shows that the present method is correct.

Application of the state space model to the system of wave energy conversion - Analytical method for wave forces on single oscillating rectangular buoy

Yonghong Zheng

Papers

On diffraction and radiation problem for a cylinder over a caisson in water of finite depth

Response Amplitude and Hydrodynamic Force for a Buoy over a Convex

Floating type double-floater ocean wave power generator

Scattering of Linear Water Waves by a Fixed and Infinitely Long Rectangular Structure Parallel to a Vertical Wall in Oblique Seas

Application of the state space model to the system of wave energy conversion - Analytical method for wave forces on single oscillating rectangular buoy