Numerical Study on the Optimal Shape and Performance of an Oscillating Water Column Using Analytic Air Damping Coefficients and Numerical Wave Tank

For the stability of offshore structures, such as offshore wind foundations, extreme wave conditions need to be taken into account. Waves from extreme events are critical from the design perspective. In a numerical wave tank, extreme waves can be modeled using focused waves. Here, linear waves are generated from a wave spectrum. The wave crests of the generated waves coincide at a preselected location and time. Focused wave generation is implemented in the numerical wave tank module of REEF3D, which has been extensively and successfully tested for various wave hydrodynamics and wave–structure interaction problems in particular and for free surface flows in general. The open-source computational fluid dynamics (CFD) code REEF3D solves the three-dimensional Navier–Stokes equations on a staggered Cartesian grid. Higher order numerical schemes are used for time and spatial discretization. For the interface capturing, the level set method is selected. In order to test the generated waves, the time series of the free surface elevation are compared with experimental benchmark cases. The numerically simulated free surface elevation shows good agreement with experimental data. In further computations, the impact of the focused waves on a vertical circular cylinder is investigated. A breaking focused wave is simulated and the associated kinematics is investigated. Free surface flow features during the interaction of nonbreaking focused waves with a cylinder and during the breaking process of a focused wave are also investigated along with the numerically captured free surface.

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MOTION OF FLOATING CAISSON USING 3D NUMERICAL WAVE TANK

Journal of Japan Society of Civil Engineers Ser B2 (Coastal Engineering) ◽

10.2208/kaigan.77.2_i_775 ◽

2021 ◽

Vol 77 (2) ◽

pp. I_775-I_780

Author(s):

Atsushi TAKAGI ◽

Masashi WATANABE ◽

Taro ARIKAWA

Keyword(s):

Numerical Wave Tank ◽

Wave Tank ◽

Numerical Wave

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Evaluation of 3-D Computational Model of Oscillating Water Column Converter with Constructal Design with Three Degrees of Freedom and Limited Chimney Height

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.407.128 ◽

2021 ◽

Vol 407 ◽

pp. 128-137

Author(s):

Vinícius Bloss ◽

Camila Fernandes Cardozo ◽

Flávia Schwarz Franceschini Zinani ◽

Luiz Alberto Oliveira Rocha

Keyword(s):

Water Column ◽

Wave Energy ◽

Degrees Of Freedom ◽

Numerical Study ◽

Mechanical Energy ◽

Ocean Waves ◽

Response Surfaces ◽

Oscillating Water Column ◽

Promising Source ◽

Three Degrees Of Freedom

Theoretically, ocean waves contain enough mechanical energy to supply the entire world’s demand and, as of late, are seen as a promising source of renewable energy. To this end, several different technologies of Wave Energy Converters (WEC) have been developed such as Oscillating Water Column (OWC) devices. OWCs are characterized by a chamber in which water oscillates inside and out in a movement similar to that of a piston. This movement directs air to a chimney where a turbine is attached to convert mechanical energy. The analysis conducted was based on the Constructive Design Method, in which a numerical study was carried out to obtain the geometric configuration that maximized the conversion of wave energy into mechanical energy. Three degrees of freedom were used: the ratio of height to length of the hydropneumatic chamber (H1/L), the ratio of the height of the chimney to its diameter (H2/d) and the ratio of the width of the hydropneumatic chamber to the width of the wave tank (W/Z). A Design of Experiments (DoE) technique coupled with Central Composite Design (CCD) allowed the simulation of different combinations of degrees of freedom. This allowed the construction of Response Surfaces and correlations for the efficiency of the system depending on the degrees of freedom (width and height of the chamber), as well as the optimization of the system based on the Response Surfaces.

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