Effects of blade parameters on the hydrodynamic performance of an impulse turbine of oscillation water column wave energy

2021 ◽  
Vol 224 ◽  
pp. 108760
Author(s):  
Xiu Wang ◽  
Yan Yan ◽  
Wen-Quan Wang
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Hydrodynamic Performance ◽  
Impulse Turbine

Performance of a Shore Fixed Oscillating Water Column Device for Different Bottom Slopes and Front Wall Drafts: A Study Based on Computational Fluid Dynamics and BIEM

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Piyush Mohapatra ◽  
K. G. Vijay ◽  
Anirban Bhattacharyya ◽  
Trilochan Sahoo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Water Column ◽  
Wave Energy ◽  
High Efficiency ◽  
Boundary Integral ◽  
Hydrodynamic Performance ◽  
Chamber Pressure ◽  
Front Wall ◽  
Oscillating Water Column

Abstract Oscillating water column (OWC) wave energy converters are one of the most widely researched devices for ocean wave energy harvesting. This study investigates the hydrodynamic performance of a shore-fixed OWC device for different bottom slopes using two numerical approaches, namely, computational fluid dynamics (CFD) and boundary integral equation method (BIEM). In the BIEM method, the boundary value problem is solved in two-dimensional Cartesian coordinates using the linear water wave theory. The CFD model uses a numerical wave tank (NWT) built using the volume of fluid (VOF) method. Numerical computations are carried out for different sloped bottom geometries and front wall drafts to analyze the hydrodynamic efficiency. There is a general agreement between CFD and BIEM results in terms of resonating behavior of the device. It is observed that the front wall draft has a more significant effect, a lower draft leading to a wider frequency band for optimum conversion at high efficiency. While the BIEM-based analysis resulted in improved performance curve for few of the steeper slopes, the CFD study predicted a lower peak efficiency for the same slopes due to the consideration of real fluid characteristics. Detailed performance comparisons are presented using the time histories of free surface elevation, chamber pressure, and streamlines at different time instants within the OWC chamber.

scholarly journals Optimal design of air turbines for oscillating water column wave energy systems: A review

2017 ◽  
Vol 8 (1) ◽  
pp. 37-49 ◽  
Author(s):  
Tapas Kumar Das ◽  
Paresh Halder ◽  
Abdus Samad
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Guide Vane ◽  
Optimization Techniques ◽  
Maximum Efficiency ◽  
Oscillating Water Column ◽  
Peak Efficiency ◽  
Wells Turbine ◽  
Impulse Turbine ◽  
Operating Range

Oscillating water column wave energy harvesting system uses pneumatic power to run a turbine and generate power. Both reaction (mainly Wells turbine) and impulse type turbines are tested in oscillating water column system and the performances are investigated. Reaction turbines are easy to install, and the operating range is narrow and possesses higher peak efficiency. On the contrary, impulse turbines have the wider operating range and lower peak efficiency. Some of the key parameters for Wells turbine are solidity, tip clearance, and the hub-to-tip ratio. Significant performance improvement is possible by redesigning the turbines using optimization techniques. Till date, surrogate modeling and an automated optimization library OPAL are commonly used in optimization of oscillating water column air turbines. In this article, various types of oscillating water column turbines are reviewed, and optimization techniques applied to such turbines are discussed. The Wells turbine with guide vane has the maximum efficiency, whereas the axial-impulse turbine with pitch-controlled guide vane has the widest operating range. Turbines with optimized geometry have better overall performance than other turbines.

Numerical investigation of front-wall inclination effects on the hydrodynamic performance of a fixed oscillation water column wave energy converter

2018 ◽  
Vol 233 (2) ◽  
pp. 262-271
Author(s):  
M Anbarsooz ◽  
H Rashki ◽  
A Ghasemi
Keyword(s):  
Water Column ◽  
Wave Height ◽  
Wave Energy ◽  
Nonlinear Waves ◽  
Absorption Efficiency ◽  
Hydrodynamic Performance ◽  
Front Wall ◽  
Oscillating Water Column ◽  
Wave Tank ◽  
Highly Nonlinear

One of the main geometrical parameters of the fixed oscillating water column wave energy converters is the inclination angle of front wall. In this study, the effects of this parameter on the hydrodynamic performance of an oscillating water column is investigated using a fully nonlinear two-dimensional numerical wave tank, which is developed using the Ansys Fluent 15.0 commercial software. The accuracy of the developed wave tank is first examined by simulating an oscillating water column, having a front wall normal to the water-free surface, subjected to linear, small amplitude incident waves. The resultant absorption efficiencies are compared with available analytical data in the literature, where a good agreement was observed. Next, the simulations are performed for strongly nonlinear waves, up to the wave steepness of 0.069 ( H/L = 0.069), where H is the wave height and L is the wave length. Results show that the absorption efficiency of the oscillating water column decreases considerably as the wave height increases. Moreover, the maximum wave energy absorption efficiency for the highly nonlinear waves occurs at a pneumatic damping coefficient lower than that of the linear theory. Then, the absorption efficiency of the oscillating water column is determined for eight various front wall configurations at various incident wave periods. Results show that, the front walls that are slightly bent towards the inner region of the oscillating water column chamber are more efficient at some wave periods in comparison with the cases studied in this paper.

A Tethered Multiple Oscillating Water Column Wave Energy Device: From Concept to Deployment

2002 ◽  
Author(s):  
John Chudley ◽  
Y. Ming Dai ◽  
Fraser Johnson
Keyword(s):  
Engineering Design ◽  
Water Column ◽  
Wave Energy ◽  
Phase Locking ◽  
Wave Climate ◽  
Oscillating Water Column ◽  
Impulse Turbine ◽  
Energy Device ◽  
Local Wave ◽  
The Individual

This paper discusses the research and design methodology employed in the development of a tethered Multiple Oscillating Water Column (MOWC) wave energy device – from concept to deployment. The fundamental aim of the project was the design and deployment of a scaled floating MOWC wave energy device capable of generating physical data from sea trials. The MOWC collector component incorporated oscillating columns connected to a self-rectifying impulse turbine via individual settling chambers. The device has a water draught of 12m and an air draught of 3m. It is of cylindrical design with an overall diameter of 4.4m, displacing 10t The present unit is rated to at 5 kW power output through restrictions of the internal airflows. Research indicates that a full-scale unit 5 times bigger than the scaled device would be capable of generating 500 – 750 kW in a moderately rough sea. The paper addresses the complex problems associated with floating MOWC devices and suggests methods to enable accurate modeling and matching of internal components. Topics discussed include: concept recognition, hydrodynamic motion interaction with OWC, local resource evaluation, turbine selection, power generation and dissipation, moorings, data monitoring, telemetry and performance evaluation. Mathematical simulations and tank testing were used to develop the concept to a stage where an engineering design could be generated. The use of mathematical modelling presented the project with several specific problems that have been highlighted within the paper. Tank testing enabled the project to overcome these difficulties and developed an engineering design tuned to the local wave climate. Initial research has indicated that the combination of individual Oscillating Water Columns (OWC) of different draughts increases the efficiency of this design when compared to a typical single OWC device. Results also indicated that the channeling of individual air masses through a self-rectifying impulse turbine would produce a self-regulated electrical output via phase locking of the individual columns.

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