EFFECTS OF NUMERICAL DISSIPATION AND DISPERSION ON ACOUSTIC PREDICTIONS FROM A TIME-DOMAIN FINITE DIFFERENCE TECHNIQUE FOR NON-LINEAR WAVE DYNAMICS

This paper presents the findings from using several commercial computational fluid dynamics codes in a joint numerical and experimental project to simulate WRASPA, a new wave energy converter (WEC) device. A series of fully 3D non-linear simulations of WRASPA are presented. Three commercial codes STAR-CCM, CFX and FLOW-3D are considered for simulating the WRASPA device and final results are presented based on the use of Flow-3D. Results are validated by comparison to experimental data obtained from small scale tank tests undertaken at Lancaster University (LU). The primary aim of the project is to use numerical simulation to optimize the collector geometry for power production over a range of likely wave climates. A secondary aim is to evaluate the ability of commercial codes to simulate rigid body motion in linear and non-linear wave climates in order to choose the optimal code with respect to compute speed and ease of problem setup. Issues relating to the ability of a code in terms of numerical dissipation of waves, wave absorption, wave breaking, grid generation and moving bodies will all be discussed. The findings of this paper serve as a basis for an informed choice of commercial package for such simulations. However the capability of these commercial codes is increasing with every new release.

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Genetic Optimization of Shape and Control of Non-Linear Wave Energy Converters

Volume 9: Ocean Renewable Energy ◽

10.1115/omae2020-19156 ◽

2020 ◽

Author(s):

Jiajun Song ◽

Ossama Abdelkhalik ◽

Shangyan Zou

Keyword(s):

Wave Energy ◽

Time Domain ◽

Optimization Approach ◽

Linear Wave ◽

Variable Size ◽

Wave Energy Converters ◽

Hydrostatic Force ◽

Non Linear ◽

The Time Domain ◽

Energy Converters

Abstract This paper presents an optimization approach to design ax-isymmetric wave energy converters (WECs) based on a nonlinear hydrodynamic model. This paper shows optimal nonlinear shapes of buoy can be generated by combing basic shapes in an optimal sense. The time domain non-linear Froude-Krylov force can be computed for a complex buoy shape, by adopting analytical formulas of its basic shape components. The time domain Forude-Krylov force is decomposed into its dynamic and static components, and then contribute to the calculation of the excitation force and the hydrostatic force. A non-linear control is assumed in the form of the combination of linear and nonlinear damping terms. A variable size genetic algorithm (GA) optimization tool is developed to search for the optimal buoy shape along with the optimal control coefficients simultaneously. Chromosome of the GA tool is designed to improve computational efficiency and to leverage variable size genes to search for the optimal non-linear buoy shape. Different criteria of wave energy conversion can be implemented by the variable size GA tool. Simulation results presented in this paper show that it is possible to find non-linear buoy shapes and non-linear controllers that take advantage of non-linear hydrodynamics to improve energy harvesting efficiency with out adding reactive terms to the system.

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Large deflection of plates and beams obeying non-linear stress—strain laws

Journal of Strain Analysis ◽

10.1243/03093247v093178 ◽

1974 ◽

Vol 9 (3) ◽

pp. 178-184 ◽

Cited By ~ 1

Author(s):

K R Rushton ◽

P M Hook

Keyword(s):

Finite Difference ◽

Large Deflection ◽

Experimental Results ◽

Large Deflections ◽

Rectangular Plates ◽

Dynamic Relaxation ◽

Stress Strain ◽

Finite Difference Technique ◽

Non Linear ◽

Alternative Solutions

The large deflections of rectangular plates and beams obeying a non-linear stress-strain law are examined. Solutions are obtained by use of dynamic relaxation, a numerical finite-difference technique. Comparisons are made with alternative solutions and experimental results. The effects of varying parameters in the non-linear expressions are considered.

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