Hydrodynamic Analysis of a Vertical Axisymmetric Oscillating Water Column Device Floating in Finite Depth Waters

2012 ◽  
Author(s):  
Spyros A. Mavrakos ◽  
Dimitrios N. Konispoliatis
Keyword(s):  
Water Column ◽  
Wall Thickness ◽  
Vertical Cylinder ◽  
Finite Depth ◽  
Wave Forces ◽  
Oscillating Water Column ◽  
Wells Turbine ◽  
Present Contribution ◽  
Outer Atmosphere ◽  
Incident Waves

A floating oscillating water column device (OWC) consists of a vertical cylinder, with a finite wall thickness, partly submerged as an open-bottom chamber in which air is trapped above the inner water free surface. The chamber is connected with the outer atmosphere by a duct housing an air turbine. Forced by incident waves from any direction, the water surface inside pushes the dry air above through a Wells turbine system to generate power. In the present contribution the volume flows, the wave forces, the added mass and damping coefficients and the mean second-order loads for various configurations of OWC devices are being presented. Finally, it is tested how differentiations in the device’s geometry (wall thickness, draught, shape of the chamber, turbine characterises) affect the inner pressure and as a result the absorbed power by the device.

scholarly journals Computational Fluid Dynamics Model of Wells Turbine for Oscillating Water Column System: A Review

2021 ◽  
Vol 2053 (1) ◽  
pp. 012013
Author(s):  
N. Abdul Settar ◽  
S. Sarip ◽  
H.M. Kaidi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Water Column ◽  
Cfd Simulation ◽  
Oscillating Water Column ◽  
Wells Turbine ◽  
Flow Problems ◽  
Cfd Models ◽  
Column System ◽  
Cfd Method

Abstract Wells turbine is an important component in the oscillating water column (OWC) system. Thus, many researchers tend to improve the performance via experiment or computational fluid dynamics (CFD) simulation, which is cheaper. As the CFD method becomes more popular, the lack of evidence to support the parameters used during the CFD simulation becomes a big issue. This paper aims to review the CFD models applied to the Wells turbine for the OWC system. Journal papers from the past ten years were summarized in brief critique. As a summary, the FLUENT and CFX software are mostly used to simulate the Wells turbine flow problems while SST k-ω turbulence model is the widely used model. A grid independence test is essential when doing CFD simulation. In conclusion, this review paper can show the research gap for CFD simulation and can reduce the time in selecting suitable parameters when involving simulation in the Wells turbine.

Analysis of the Wells Turbine Structure of an Oscillating Water Column Wave Energy System

2021 ◽  
pp. 53-62
Author(s):  
Mohamed Ali Jemni ◽  
Hamdi Hentati ◽  
Sawsan Elmbarki ◽  
Mohamed Salah Abid
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Energy System ◽  
Oscillating Water Column ◽  
Wells Turbine

Efficiency Optimization in Low Inertia Wells Turbine-Oscillating Water Column Devices

2013 ◽  
Vol 28 (3) ◽  
pp. 553-564 ◽  
Author(s):  
Salvador Ceballos ◽  
Judy Rea ◽  
Iraide Lopez ◽  
Josep Pou ◽  
Eider Robles ◽  
...  
Keyword(s):  
Water Column ◽  
Oscillating Water Column ◽  
Wells Turbine ◽  
Efficiency Optimization

Effect of Oscillating Water Column Chamber Inclination on the Performance of a Savonius Rotor

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Deepak D. Prasad ◽  
M. Rafiuddin Ahmed ◽  
Young-Ho Lee
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Hollow Structure ◽  
Flow Characteristics ◽  
Wave Crest ◽  
Oscillating Water Column ◽  
Sea State ◽  
Wave Condition ◽  
Improved Performance ◽  
Incident Waves

Abstract The power potential in the waves that hit all the coasts worldwide has been estimated to be of the order of 1 TW. Each wave crest transmits 10–50 kW/m of energy, which is 15–20 times higher than wind or solar energies. The availability of wave energy is 90% compared to 30% for wind and solar energies. The oscillating water column (OWC), which is the most investigated wave energy converter consists of a partially submerged hollow structure positioned either vertically or inclined. The bidirectional airflow above the water column drives a turbine. The conventional OWCs experience flow separation at the sharp corners of the chamber. To address this issue, researchers have proposed inclining the chamber at an angle with respect to the incident waves to improve the flow characteristics. In the present work, the effect of OWC inclination on rotor performance is studied using the computational fluid dynamics (CFD) code ansys-cfx. The results highlight that the 55 deg inclined OWC showed improved performance compared to the conventional OWC and modified OWC (optimized in a previous work). The maximum power for the inclined OWC was 13% higher than that for the rotor in the modified OWC and 28% than that in the conventional OWC at mean wave condition. The 55 deg inclined OWC recorded peak rotor power of 23.2 kW with an efficiency of 27.6% at the mean sea state. The peak power and efficiency at maximum sea state were 26.5 kW and 21.5%, respectively.

Effect of Oscillating Water Column Chamber Inclination on the Performance of a Savonius Rotor

2018 ◽  
Author(s):  
Deepak D. Prasad ◽  
Mohammed Rafiuddin Ahmed ◽  
Young-Ho Lee
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Hollow Structure ◽  
Flow Characteristics ◽  
Wave Crest ◽  
Oscillating Water Column ◽  
Sea State ◽  
Wave Condition ◽  
Improved Performance ◽  
Incident Waves

The global power potential of the waves that hit all the coasts worldwide has been estimated to be in the order of 1 TW. On an average, each wave crest transmits 10–50 kW/m of energy and this corresponds to 15 to 20 times more energy per meter than wind or solar energies. Wave energy is environmentally friendly and is the most consistent of all the intermittent sources. While wind, solar and wave are all intermittent, wave is the most consistent. Availability of waves is 90% compared to 30% for wind and solar energy. The oscillating water column (OWC) is the most investigated wave energy converter (WEC). OWC is a partially submerged hollow structure positioned, either vertically or at an angle. The bidirectional flow of air above the water column is used to drive a turbine. Majority of the OWC devices have chambers which are perpendicular to the incident waves. These conventional OWCs suffer severely from flow separation that occurs at the sharp corners of the chamber. In order to address this issue, researchers have proposed inclining the chamber at an angle with respect to the incident waves. This improves the flow characteristics. In addition to this, the flow in the chamber which ultimately decides the turbine performance, also increases. In the present study, the effect of OWC inclination on rotor performance was numerically studied using commercial computational fluid dynamics (CFD) code ANSYS CFX. The results highlight that the 55° inclined OWC showed improved performance when compared to the conventional OWC and current OWC. The maximum power for the inclined OWC was 13% higher than that recorded for the rotor in the current OWC and 28% than that recorded in the conventional OWC at mean wave condition. The 55° inclined OWC recorded peak rotor power of 23.2 kW which corresponded to an efficiency of 27.6% at the mean sea state. The peak power and efficiency at maximum sea state was 26.5 kW and 21.5% respectively. Higher oscillation was observed in the 55° inclined OWC. The combination of increased flow rate and energy in the flow lead to better performance of the 55° inclined OWC.

scholarly journals Self-Adaptive Global-Best Harmony Search Algorithm-Based Airflow Control of a Wells-Turbine-Based Oscillating-Water Column

2020 ◽  
Vol 10 (13) ◽  
pp. 4628 ◽  
Author(s):  
Fares M’zoughi ◽  
Izaskun Garrido ◽  
Aitor J. Garrido ◽  
Manuel De La Sen
Keyword(s):  
Water Column ◽  
Search Algorithm ◽  
Harmony Search ◽  
Harmony Search Algorithm ◽  
The Self ◽  
Oscillating Water Column ◽  
Wells Turbine ◽  
Control Scheme ◽  
Tuning Methods ◽  
Self Adaptive

The Harmony Search algorithm has attracted a lot of interest in the past years because of its simplicity and efficiency. This led many scientists to develop various variants for many applications. In this paper, four variants of the Harmony search algorithm were implemented and tested to optimize the control design of the Proportional-Integral-derivative (PID) controller in a proposed airflow control scheme. The airflow control strategy has been proposed to deal with the undesired stalling phenomenon of the Wells turbine in an Oscillating Water Column (OWC). To showcase the effectiveness of the Self-Adaptive Global Harmony Search (SGHS) algorithm over traditional tuning methods, a comparative study has been carried out between the optimized PID, the traditionally tuned PID and the uncontrolled OWC system. The results of optimization showed that the Self-Adaptive Global Harmony Search (SGHS) algorithm adapted the best to the problem of the airflow control within the wave energy converter. Moreover, the OWC performance is superior when using the SGHS-tuned PID.

scholarly journals Control strategies for combining local energy storage with wells turbine oscillating water column devices

2015 ◽  
Vol 83 ◽  
pp. 1097-1109 ◽  
Author(s):  
Salvador Ceballos ◽  
Judy Rea ◽  
Eider Robles ◽  
Iraide Lopez ◽  
Josep Pou ◽  
...  
Keyword(s):  
Energy Storage ◽  
Water Column ◽  
Control Strategies ◽  
Local Energy ◽  
Oscillating Water Column ◽  
Wells Turbine

Design synthesis of oscillating water column wave energy converters: Performance matching

1997 ◽  
Vol 211 (6) ◽  
pp. 489-505 ◽  
Author(s):  
R Curran ◽  
T P Stewart ◽  
T J T Whittaker
Keyword(s):  
Water Column ◽  
Limited Range ◽  
Power Converter ◽  
Analytical Models ◽  
Wave Power ◽  
Oscillating Water Column ◽  
Wells Turbine ◽  
Design Synthesis ◽  
Wave Energy Converters ◽  
Pneumatic Power

The matching of a Wells air turbine to an oscillating water column (OWC) is addressed, with particular reference to design synthesis at the Islay prototype wave power converter. The level of damping applied by the turbine must optimize the hydraulic performance of the OWC in order to facilitate efficient conversion from wave power to pneumatic power. Furthermore, a Wells turbine is only able to convert pneumatic power to mechanical power over a limited range of flow coefficients. Therefore, the efficient operational range of the turbine must extend over a sufficient and optimal proportion of the range of flow coefficients generated by the OWC. Suitable analytical models that describe the behaviour of the system are presented and subsequently the wave conditions and conversion performance at the Islay plant are outlined in order to exemplify the design synthesis to be achieved.

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