EVALUATION OF CERAMIC AND MEMBRANE DIFFUSERS UNDER DIFFERENT WATER COLUMNS WITH PULSATING AIRFLOW METHOD

2020 ◽  
Vol 21 (2) ◽  
pp. 145-167 ◽  
Author(s):  
Ahmed Ali Alkhafaji ◽  
Ryoichi Samuel Amano
Keyword(s):  
Water Columns

Comparison of the performance of oscillating water column devices based on arrangements of water columns

2020 ◽  
Vol 14 (3) ◽  
pp. 7082-7093
Author(s):  
Jahirwan Ut Jasron ◽  
Sudjito Soeparmani ◽  
Lilis Yuliati ◽  
Djarot B. Darmadi
Keyword(s):  
Wave Propagation ◽  
Water Column ◽  
Water Depth ◽  
Graphical Form ◽  
Wave Power ◽  
Oscillating Water Column ◽  
Power Absorption ◽  
Water Columns ◽  
Single Column ◽  
Parallel Arrangement

The hydrodynamic performance of oscillating water column (OWC) depends on the depth of the water, the size of the water column and its arrangement, which affects the oscillation of the water surface in the column. An experimental method was conducted by testing 4 water depths with wave periods of 1-3 s. All data recorded by the sensor is then processed and presented in graphical form. The research focused on analyzing the difference in wave power absorption capabilities of the three geometric types of OWC based on arrangements of water columns. The OWC devices designed as single water column, the double water column in a series arrangement which was perpendicular to the direction of wave propagation, and double water column in which the arrangement of columns was parallel to the direction of wave propagation. This paper discussed several factors affecting the amount of power absorbed by the device. The factors are the ratio of water depth in its relation to wavelength (kh) and the inlet openings ratio (c/h) of the devices. The test results show that if the water depth increases in the range of kh 0.7 to 0.9, then the performance of the double chamber oscillating water column (DCOWC) device is better than the single chamber oscillating water column (SCOWC) device with maximum efficiency for the parallel arrangement 22,4%, series arrangement 20.8% and single column 20.7%. However, when referring to c/h, the maximum energy absorption efficiency for a single column is 27.7%, double column series arrangement is 23.2%, and double column parallel arrangement is 29.5%. Based on the results of the analysis, DCOWC devices in parallel arrangement showed the ability to absorb better wave power in a broader range of wave frequencies. The best wave of power absorption in the three testing models occurred in the wave period T = 1.3 seconds.

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.

Seasonal Variability in Middepth Gyral Circulation Patterns in the Central East/Japan Sea as Revealed by Long-Term Argo Data

2016 ◽  
Vol 46 (3) ◽  
pp. 937-946 ◽  
Author(s):  
Sok Kuh Kang ◽  
Young Ho Seung ◽  
Jong Jin Park ◽  
Jae-Hun Park ◽  
Jae Hak Lee ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Seasonal Variability ◽  
Japan Sea ◽  
Circulation Pattern ◽  
Japan Basin ◽  
Wind Stress Curl ◽  
Argo Data ◽  
Circulating Water ◽  
Significant Seasonal Variation ◽  
Water Columns

AbstractTrajectories of Argo floats deployed in the East/Japan Sea from 2001 to 2014 reveal that the middepth gyral circulation pattern of the Japan basin, the central part of the East/Japan Sea, undergoes a seasonal variation. The middepth circulation of the Japan basin is found to be characterized usually by the gyres trapped to the east of the Bogorov Rise (E-gyres) and those extending farther westward into the whole basin (BW-gyres). The E-gyre trajectories are generally associated with the turning of the floats toward deeper regions off the isobaths. This occurs in winter either on the northern or eastern side of the eastern Japan basin. It seems that the upstream part of the otherwise BW-gyre is subject to a strong negative wind stress curl in winter, and there the circulating water columns are driven toward the deeper region, thus triggering the formation of the E-gyre. The topographic effect associated with the Bogorov Rise seems to interfere thereafter in the process of determining the passage of the E-gyre. Otherwise, the water columns continue to flow along the isobaths, hence maintaining the BW-gyre. To the knowledge of the authors, this is the first observational evidence of seasonal variability in the middepth gyral circulation pattern in the East/Japan Sea. It suggests that oceanic middepth circulation, usually known to be quasi steady or slowly varying on climatological time scales, might also undergo a significant seasonal variation as it does in the East/Japan Sea.

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

Exploratory analyses of trichlorofluoromethane (F-11) in North Atlantic water columns

1978 ◽  
Vol 5 (8) ◽  
pp. 645-648 ◽  
Author(s):  
Paul M. Hammer ◽  
J. M. Hayes ◽  
W. J. Jenkins ◽  
R. B. Gagosian
Keyword(s):  
North Atlantic ◽  
Atlantic Water ◽  
Water Columns ◽  
North Atlantic Water

Distribution of Haloacetic Acids in the Water Columns of the Laurentian Great Lakes and Lake Malawi

2002 ◽  
Vol 36 (9) ◽  
pp. 1893-1898 ◽  
Author(s):  
Brian F. Scott ◽  
Christine Spencer ◽  
Christopher H. Marvin ◽  
David C. MacTavish ◽  
Derek C. G. Muir
Keyword(s):  
Great Lakes ◽  
Lake Malawi ◽  
Haloacetic Acids ◽  
Laurentian Great Lakes ◽  
Water Columns

Isotopic evidence for the origin of dimethylsulfide and dimethylsulfoniopropionate-like compounds in a warm, monomictic freshwater lake

2016 ◽  
Vol 13 (2) ◽  
pp. 340 ◽  
Author(s):  
Michal Sela-Adler ◽  
Ward Said-Ahmad ◽  
Orit Sivan ◽  
Werner Eckert ◽  
Ronald P. Kiene ◽  
...  
Keyword(s):  
Sulfur Compound ◽  
Sulfur Cycle ◽  
Freshwater Lake ◽  
Aquatic Environments ◽  
Dissimilatory Sulfate Reduction ◽  
Biogeochemical Processes ◽  
Multiple Sources ◽  
Isotopic Signatures ◽  
Isotopic Evidence ◽  
Water Columns

Environmental context The volatile sulfur compound, dimethylsulfide (DMS), plays a major role in the global sulfur cycle by transferring sulfur from aquatic environments to the atmosphere. Compared to marine environments, freshwater environments are under studied with respect to DMS cycling. The goal of this study was to assess the formation pathways of DMS in a freshwater lake using natural stable isotopes of sulfur. Our results provide unique sulfur isotopic evidence for the multiple DMS sources and dynamics that are linked to the various biogeochemical processes that occur in freshwater lake water columns and sediments. Abstract The volatile methylated sulfur compound, dimethylsulfide (DMS), plays a major role in the global sulfur cycle by transferring sulfur from aquatic environments to the atmosphere. The main precursor of DMS in saline environments is dimethylsulfoniopropionate (DMSP), a common osmolyte in algae. The goal of this study was to assess the formation pathways of DMS in the water column and sediments of a monomictic freshwater lake based on seasonal profiles of the concentrations and isotopic signatures of DMS and DMSP. Profiles of DMS in the epilimnion during March and June 2014 in Lake Kinneret showed sulfur isotope (δ34S) values of +15.8±2.0 per mille (‰), which were enriched by up to 4.8 ‰ compared with DMSP δ34S values in the epilimnion at that time. During the stratified period, the δ34S values of DMS in the hypolimnion decreased to –7.0 ‰, close to the δ34S values of coexisting H2S derived from dissimilatory sulfate reduction in the reduced bottom water and sediments. This suggests that H2S was methylated by unknown microbial processes to form DMS. In the hypolimnion during the stratified period DMSP was significantly 34S enriched relative to DMS reflecting its different S source, which was mostly from sulfate assimilation. In the sediments, δ34S values of DMS were depleted by 2–4 ‰ relative to porewater (HCl-extracted) DMSP and enriched relative to H2S. This observation suggests two main formation pathways for DMS in the sediment, one from the degradation of DMSP and one from methylation of H2S. The present study provides isotopic evidence for multiple sources of DMS in stratified water bodies and complex DMSP–DMS dynamics that are linked to the various biogeochemical processes within the sulfur cycle.

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