scholarly journals A NUMERICAL STUDY ON MULTI-CHAMBER OSCILLATING WATER COLUMNS

2015 ◽  
Vol 3 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Pallav KOIRALA ◽  
Shuichi NAGATA ◽  
Yasutaka IMAI ◽  
Tengen MURAKAMI ◽  
Toshiaki SETOGUCHI
Keyword(s):  
Numerical Study ◽  
Water Columns ◽  
Oscillating Water Columns

Analytical and Numerical Study of Nearshore Multiple Oscillating Water Columns

2013 ◽  
Author(s):  
Kourosh Rezanejad ◽  
Joydip Bhattacharjee ◽  
C. Guedes Soares
Keyword(s):  
Water Depth ◽  
Numerical Study ◽  
Integral Equation Method ◽  
Wave Theory ◽  
Boundary Integral ◽  
Water Columns ◽  
Finite Water Depth ◽  
Cartesian Coordinate ◽  
Oscillating Water Columns ◽  
Good Agreement

In the present study, the performance of two chamber nearshore oscillating water columns (OWCs) in finite water depth is analyzed based on the linearized water wave theory in the two dimensional Cartesian coordinate systems. The barriers are assumed to be fixed and the turbine characteristics are assumed linear with respect to the fluctuations of volume flux and pressure inside the chamber. The free surface inside the chambers is modeled as a non-plane wave surface. Two different mathematical models are employed to solve the hydrodynamic problem; the semi-analytic method of matched eigenfunction expansion and the numerical scheme of Boundary Integral Equation Method (BIEM). The numerical results are compared with the semi-analytic results and show good agreement. The effects of the distance between the barriers and the length of the barriers on the efficiency of the OWC device are investigated. The results of two chambers OWC are also compared with the results for an equivalent single OWC chamber. Further, the effect of the water depth on the capacity of the wave power absorption is discussed.

Analytical and Numerical Study of Nearshore Multiple Oscillating Water Columns

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Kourosh Rezanejad ◽  
Joydip Bhattacharjee ◽  
Carlos Guedes Soares
Keyword(s):  
Water Depth ◽  
Numerical Study ◽  
Integral Equation Method ◽  
Wave Theory ◽  
Boundary Integral ◽  
Water Columns ◽  
Finite Water Depth ◽  
Cartesian Coordinate ◽  
Oscillating Water Columns ◽  
Good Agreement

In the present study, the performance of two chamber nearshore oscillating water columns (OWCs) in finite water depth is analyzed based on the linearized water wave theory in the two-dimensional Cartesian coordinate systems. The barriers are assumed to be fixed and the turbine characteristics are assumed linear with respect to the fluctuations of volume flux and pressure inside the chamber. The free surface inside the chambers is modeled as a nonplane wave surface. Two different mathematical models are employed to solve the hydrodynamic problem: the semi-analytic method of matched eigenfunction expansion and the numerical scheme of boundary integral equation method (BIEM). The numerical results are compared with the semi-analytic results and show good agreement. The effects of the distance between the barriers and the length of the barriers on the efficiency of the OWC device are investigated. The results of two chambers OWC are also compared with the results for an equivalent single OWC chamber. Further, the effect of the water depth on the capacity of the wave power absorption is discussed.

Analytical and numerical study of dual-chamber oscillating water columns on stepped bottom

2015 ◽  
Vol 75 ◽  
pp. 272-282 ◽  
Author(s):  
K. Rezanejad ◽  
J. Bhattacharjee ◽  
C. Guedes Soares
Keyword(s):  
Numerical Study ◽  
Dual Chamber ◽  
Water Columns ◽  
Oscillating Water Columns

scholarly journals Performance Analysis on the Use of Oscillating Water Column in Barge-Based Floating Offshore Wind Turbines

Mathematics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 475
Author(s):  
Payam Aboutalebi ◽  
Fares M’zoughi ◽  
Izaskun Garrido ◽  
Aitor J. Garrido
Keyword(s):  
Wind Turbines ◽  
Positive Impact ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Water Columns ◽  
Numerical Tools ◽  
Oscillating Water Columns ◽  
The Given ◽  
The Waves

Undesired motions in Floating Offshore Wind Turbines (FOWT) lead to reduction of system efficiency, the system’s lifespan, wind and wave energy mitigation and increment of stress on the system and maintenance costs. In this article, a new barge platform structure for a FOWT has been proposed with the objective of reducing these undesired platform motions. The newly proposed barge structure aims to reduce the tower displacements and platform’s oscillations, particularly in rotational movements. This is achieved by installing Oscillating Water Columns (OWC) within the barge to oppose the oscillatory motion of the waves. Response Amplitude Operator (RAO) is used to predict the motions of the system exposed to different wave frequencies. From the RAOs analysis, the system’s performance has been evaluated for representative regular wave periods. Simulations using numerical tools show the positive impact of the added OWCs on the system’s stability. The results prove that the proposed platform presents better performance by decreasing the oscillations for the given range of wave frequencies, compared to the traditional barge platform.

scholarly journals Switching Control Strategy for Oscillating Water Columns Based on Response Amplitude Operators for Floating Offshore Wind Turbines Stabilization

2021 ◽  
Vol 11 (11) ◽  
pp. 5249
Author(s):  
Payam Aboutalebi ◽  
Fares M’zoughi ◽  
Itziar Martija ◽  
Izaskun Garrido ◽  
Aitor J. Garrido
Keyword(s):  
Switching Control ◽  
Response Amplitude ◽  
Offshore Wind ◽  
Oscillating Water Column ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Water Columns ◽  
Switching Control Strategy ◽  
Response Amplitude Operators ◽  
Oscillating Water Columns

In this article, a new strategy for switching control has been proposed with the aim of reducing oscillations in floating offshore wind turbines. Such oscillations lead to a shortage in the system’s efficiency, lifespan and harvesting capability of wind and wave energies. In order to study the decreasing of undesired oscillations in the system, particularly in pitch and top tower fore-aft movements, a square-shaped platform barge equipped with four symmetric oscillating water columns has been considered. The oscillating water columns’ air flux valves allow to operate the air columns so that to control the barge movements caused by oscillatory motion of the waves. In order to design the control scheme, response amplitude operators have been used to evaluate the performance of the system for a range of wave frequency profiles. These response amplitude operators analysis makes it possible to implement a switching control strategy to adequately regulate the valves opening/closing transition. The obtained results show that the proposed controlled oscillating water column-based barge present a better performance compared to the traditional barge one. In the case study with the period of 10 s, the results indicate the significant oscillation reduction for the controlled oscillating water column-based system compared to the standard barge system by 30.8% in pitch angle and 25% in fore-aft displacement.

On the Array of Wave Energy Converters: The Case of the Coaxial-Duct OWC

2018 ◽  
Author(s):  
J. C. C. Portillo ◽  
J. C. C. Henriques ◽  
R. P. F. Gomes ◽  
L. M. C. Gato ◽  
A. F. O. Falcão
Keyword(s):  
Wave Energy ◽  
Oscillating Water Column ◽  
Economic Activities ◽  
Energy Converter ◽  
Diverse Range ◽  
Wave Energy Converters ◽  
Large Size ◽  
New Findings ◽  
Water Columns ◽  
Oscillating Water Columns

This work focuses on the initial performance assessment of an array of coaxial-duct (CD) oscillating-water-columns (owc’s) with potential to be used as multipurpose platform for the creation of value in a diverse range of offshore economic activities. The coaxial-duct owc (CD-owc) is an axisymmetric oscillating-water-column wave energy converter that has been studied for both small-size and large-size applications. This work focuses on buoys of 12 meter diameter distributed in an array of five devices, rigidly attached to each other, to form a cluster of owc’s. The objective of the study is to assess the performance of the array with this configuration and estimate the effect of parameters such as distance between devices, various modes of movements, and other constraints on the overall power output of the array. Results of different cases are compared to the performance of an isolated device to determine the interference effect of other devices. Some results validate previous research conclusions and new findings on the behavior coaxial-duct owc are presented.

Numerical Assessment on Primary Wave Energy Conversion of Oscillating Water Columns

2014 ◽  
Author(s):  
Wanan Sheng ◽  
Ray Alcorn ◽  
Tony Lewis
Keyword(s):  
Dynamic System ◽  
Energy Conversion ◽  
Wave Energy ◽  
Primary Wave ◽  
Wave Energy Conversion ◽  
Wave Energy Converters ◽  
Numerical Assessment ◽  
Water Columns ◽  
Oscillating Water Columns ◽  
Energy Converters

Oscillating water column (OWC) wave energy converters (WECs) are probably the simplest and most promising wave energy converters due to their good feasibility, reliability and survivability in practical wave energy conversions and also regarded as the most studied and developed when compared to other types of the wave energy converters. This research aims to develop a reliable numerical tool to assess the performance of the OWC wave energy converters, particularly in the primary wave energy conversion. In the numerical assessment tool, the hydrodynamics of the device and thermodynamics of the air chamber can be studied separately. However, for the complete dynamic system when a power takeoff (PTO) system is applied, these two dynamic systems are fully coupled in time-domain, in which the PTO can have a simple mathematical expression as the relation between the pressure difference across the PTO (the chamber pressure) and its flowrate through the PTO. And the application of a simple PTO pressure-flowrate relation very much simplifies the complicated aerodynamics and thermodynamics in the air turbine system so the whole dynamic system can be simplified. The methodology has been applied to a generic OWC device and the simulation results have been compared to the experimental data. It is shown that the developed numerical method is reliable in and capable of assessing the primary wave energy conversion of oscillating water columns.

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