Pub Date : 2014-11-24DOI: 10.1109/OCEANS-TAIPEI.2014.6964588
Xu Xing-an, Wu Xiong-bin, Pi Xiao-shan, Lu Xiong-jiu
In distributed MIMO (multiple-input-multiple-output)-HFSWR (high frequency surface wave radar), multiple detection modes are introduced to enrich the detection information, however making ionospheric clutter more complicated. In this paper, a distributed MIMO-HFSWR system involving three monostatic radars is introduced. Sea echo and ionospheric clutters from different paths are received simultaneously by MIMO system. Characteristic of ionospheric clutter in range domain and Doppler domain are analyzed with measured data. It is discovered that the correlation of ionospheric clutters from different paths is higher than of sea echoes. Based on this, a novel method for clutter suppression is proposed via adaptive filter using clutters from different paths as secondary data. Experimental results show that the analysis and processing method are feasible and effective.
{"title":"Ionospheric clutter analysis and suppression in a distributed MIMO-HFSWR system","authors":"Xu Xing-an, Wu Xiong-bin, Pi Xiao-shan, Lu Xiong-jiu","doi":"10.1109/OCEANS-TAIPEI.2014.6964588","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964588","url":null,"abstract":"In distributed MIMO (multiple-input-multiple-output)-HFSWR (high frequency surface wave radar), multiple detection modes are introduced to enrich the detection information, however making ionospheric clutter more complicated. In this paper, a distributed MIMO-HFSWR system involving three monostatic radars is introduced. Sea echo and ionospheric clutters from different paths are received simultaneously by MIMO system. Characteristic of ionospheric clutter in range domain and Doppler domain are analyzed with measured data. It is discovered that the correlation of ionospheric clutters from different paths is higher than of sea echoes. Based on this, a novel method for clutter suppression is proposed via adaptive filter using clutters from different paths as secondary data. Experimental results show that the analysis and processing method are feasible and effective.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"160 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134108168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-11-24DOI: 10.1109/OCEANS-TAIPEI.2014.6964496
Bo Wang, B. Chapron, R. Garello
The polarization dependent and independent scattering contributions of the sea surface could be separated using complex scattering matrix better than using the NRCS (Normalized Radar Cross Section) [1]. By achieving this separation, a polarimetric generalized K distribution (Pol-K) motivated by ENL analysis had been established. It is different from traditional speckle models which consider only the direct radar measurements and ignore the different scattering information inside pixel areas. The principle of this statistical modelling is based on the physical generation of speckle for each scattering mechanisms, i.e., polarization dependent Bragg and independent Scalar contributions. K distribution is a special case of PolK when the phase parameter α = 0. For the separated scattering contributions, K distribution describes the `tail' shape of their histograms, but overestimates the peak `height'. This disadvantage disables K distribution for oil slick detection using the separated scattering contributions. In this work, we test the capability of Pol-K distribution for oil slick detection on the RADARSAT-2 sea surface imagery, for which the peak `height' is an important property.
{"title":"Pol-K distribution applied to detect oil slick on RADARSAT-2 sea surface imagery","authors":"Bo Wang, B. Chapron, R. Garello","doi":"10.1109/OCEANS-TAIPEI.2014.6964496","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964496","url":null,"abstract":"The polarization dependent and independent scattering contributions of the sea surface could be separated using complex scattering matrix better than using the NRCS (Normalized Radar Cross Section) [1]. By achieving this separation, a polarimetric generalized K distribution (Pol-K) motivated by ENL analysis had been established. It is different from traditional speckle models which consider only the direct radar measurements and ignore the different scattering information inside pixel areas. The principle of this statistical modelling is based on the physical generation of speckle for each scattering mechanisms, i.e., polarization dependent Bragg and independent Scalar contributions. K distribution is a special case of PolK when the phase parameter α = 0. For the separated scattering contributions, K distribution describes the `tail' shape of their histograms, but overestimates the peak `height'. This disadvantage disables K distribution for oil slick detection using the separated scattering contributions. In this work, we test the capability of Pol-K distribution for oil slick detection on the RADARSAT-2 sea surface imagery, for which the peak `height' is an important property.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114794215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A method for Unmanned Surface Vehicle (USV) to follow linear path is proposed, considering both position error and course error. Based on dynamic model of the USV which is thrust with twin fixed propellers driven by DC electric motors, Cross Track Error and Line of Sight are combined into DIDO controller based on PD. The simulation experiment is conducted and compared with the method using Cross Track Error only. The results show that the proposed method performs better than the method using only Cross Track Error when the heading angle error is large.
{"title":"PD based DIDO control method for unmanned surface vehicle to follow linear path","authors":"Jianhua Wang, Mengkai Zhao, Xiaoyan Pei, Jianxin Chu","doi":"10.1109/OCEANS-TAIPEI.2014.6964529","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964529","url":null,"abstract":"A method for Unmanned Surface Vehicle (USV) to follow linear path is proposed, considering both position error and course error. Based on dynamic model of the USV which is thrust with twin fixed propellers driven by DC electric motors, Cross Track Error and Line of Sight are combined into DIDO controller based on PD. The simulation experiment is conducted and compared with the method using Cross Track Error only. The results show that the proposed method performs better than the method using only Cross Track Error when the heading angle error is large.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122383381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-11-24DOI: 10.1109/OCEANS-TAIPEI.2014.6964403
Peng Xiao, Kunde Yang, Bo Lei, Honglei Wang
Forward scattering is a special phenomenon for bi-static sonars, and it has received much attention in recent years because it can provide a lot of useful information for estimations. In this paper, two kinds of speed estimation method are proposed for forward scattering. Very simple geometrical principles are used in the two methods, and the complex acoustic field is not needed to be calculated when executing the estimation. The simulation and experiment results proved the validity of these methods.
{"title":"Application of forward scattering phenomenon: Speed estimation for intruder","authors":"Peng Xiao, Kunde Yang, Bo Lei, Honglei Wang","doi":"10.1109/OCEANS-TAIPEI.2014.6964403","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964403","url":null,"abstract":"Forward scattering is a special phenomenon for bi-static sonars, and it has received much attention in recent years because it can provide a lot of useful information for estimations. In this paper, two kinds of speed estimation method are proposed for forward scattering. Very simple geometrical principles are used in the two methods, and the complex acoustic field is not needed to be calculated when executing the estimation. The simulation and experiment results proved the validity of these methods.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116412404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-11-24DOI: 10.1109/OCEANS-TAIPEI.2014.6964489
D. Kitazawa, K. Ouchi
The intensive cultures have expanded rapidly due to their good productivity. However, the sustainability of intensive shrimp culture is increasingly being questioned. Many problems like disease due to virus, excessive nutrient enrichment, and hypoxic condition around the bottom soil are reported in the intensive culture ponds. In order to solve such problems, the water quality of the culture pond is managed every time. A paddle wheel aerator is generally installed per 500 to 1000 m2 in the intensive culture pond. The purposes of the paddle wheel aerator are to supply oxygen in hypoxic water and to transport sludge to the center of the pond. However, a paddle wheel aerator requires much electric power and sometimes occupies the cost more than half of the sales of shrimps. The present study proposes the use of the density current generator, which sucks water from upper and lower layers, and pushes out the mixed water in the middle layer. The purpose of the present study is to analyze numerically the performance of the density current generator for energy-saving shrimp culture. The numerical model is MEC (Marine Environmental Committee) ocean model, which contains the numerical simulation tool of hydrodynamic and ecosystem processes. Aerobic and anaerobic organic matters are considered in the benthic ecosystem model. The vertical profile of water current velocity around a paddle wheel aerator and a density current generator was given from the observations. The effects of shrimps are given as constant values assuming that the density of shrimps is around 40 individuals per square meter, that the feed conversion ratio is 2.5, and that the emission of wastes from shrimps is divided equally into organic and inorganic matters. As a result of numerical simulation, the basic environment in the shrimp culture pond was reproduced when paddle wheel aerators are installed in the pond. Then the performance of paddle wheel aerators and density current generator was compared based on the concentrations of dissolved oxygen and sludge. Sludge can be transported by density current generator using less energy. However, sludge is not eliminated from the pond when the density current generator is used, resulting in requiring more oxygen in water. The present study is the preliminary one to predict the performance of the density current generator. The future study includes the feasibility study in the actual or scale pond, comparing the results of numerical simulation and field investigation.
{"title":"Numerical analysis of the performance of the density current generator for energy-saving shrimp culture","authors":"D. Kitazawa, K. Ouchi","doi":"10.1109/OCEANS-TAIPEI.2014.6964489","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964489","url":null,"abstract":"The intensive cultures have expanded rapidly due to their good productivity. However, the sustainability of intensive shrimp culture is increasingly being questioned. Many problems like disease due to virus, excessive nutrient enrichment, and hypoxic condition around the bottom soil are reported in the intensive culture ponds. In order to solve such problems, the water quality of the culture pond is managed every time. A paddle wheel aerator is generally installed per 500 to 1000 m2 in the intensive culture pond. The purposes of the paddle wheel aerator are to supply oxygen in hypoxic water and to transport sludge to the center of the pond. However, a paddle wheel aerator requires much electric power and sometimes occupies the cost more than half of the sales of shrimps. The present study proposes the use of the density current generator, which sucks water from upper and lower layers, and pushes out the mixed water in the middle layer. The purpose of the present study is to analyze numerically the performance of the density current generator for energy-saving shrimp culture. The numerical model is MEC (Marine Environmental Committee) ocean model, which contains the numerical simulation tool of hydrodynamic and ecosystem processes. Aerobic and anaerobic organic matters are considered in the benthic ecosystem model. The vertical profile of water current velocity around a paddle wheel aerator and a density current generator was given from the observations. The effects of shrimps are given as constant values assuming that the density of shrimps is around 40 individuals per square meter, that the feed conversion ratio is 2.5, and that the emission of wastes from shrimps is divided equally into organic and inorganic matters. As a result of numerical simulation, the basic environment in the shrimp culture pond was reproduced when paddle wheel aerators are installed in the pond. Then the performance of paddle wheel aerators and density current generator was compared based on the concentrations of dissolved oxygen and sludge. Sludge can be transported by density current generator using less energy. However, sludge is not eliminated from the pond when the density current generator is used, resulting in requiring more oxygen in water. The present study is the preliminary one to predict the performance of the density current generator. The future study includes the feasibility study in the actual or scale pond, comparing the results of numerical simulation and field investigation.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132040652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-11-24DOI: 10.1109/OCEANS-TAIPEI.2014.6964500
Zhongyue Chen, Hui-fang Chen, Wenham Xu
Time synchronization is of great significance in underwater acoustic (UWA) networks. Many functions, such as network protocol stack, sleep-scheduling, and localization, are based on time synchronization. Because underwater sound speed is comparatively slow, synchronization protocols encounter a long propagation latency problem, which differs from those in terrestrial sensor networks. As a result, protocols omitting propagation latency, including reference-broadcast synchronization (RBS) and timing-sync protocol for sensor networks (TPSN), are inappropriate underwater. Time synchronization for high latency acoustic networks (TSHL) is a two-phase protocol dealing with the considerable propagation time and performs better than TPSN and RBS. In this paper, a simplified time synchronization protocol based on tiny-sync is introduced. Tiny-sync features low complexity in network bandwidth, storage and processing, and achieves good accuracy in terrestrial networks. However, tiny-sync is time-consuming in UWA networks. We improve the traditional tiny-sync protocol by intensively scheduling message exchange to overcome high propagation latency problem. Simulation results show that improved tiny-sync has better performance in synchronization time than previous protocols, as well as retaining the advantage of small storage requirement in traditional tiny-sync.
{"title":"Simplified time synchronization for underwater acoustic sensor networks with high propagation latency","authors":"Zhongyue Chen, Hui-fang Chen, Wenham Xu","doi":"10.1109/OCEANS-TAIPEI.2014.6964500","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964500","url":null,"abstract":"Time synchronization is of great significance in underwater acoustic (UWA) networks. Many functions, such as network protocol stack, sleep-scheduling, and localization, are based on time synchronization. Because underwater sound speed is comparatively slow, synchronization protocols encounter a long propagation latency problem, which differs from those in terrestrial sensor networks. As a result, protocols omitting propagation latency, including reference-broadcast synchronization (RBS) and timing-sync protocol for sensor networks (TPSN), are inappropriate underwater. Time synchronization for high latency acoustic networks (TSHL) is a two-phase protocol dealing with the considerable propagation time and performs better than TPSN and RBS. In this paper, a simplified time synchronization protocol based on tiny-sync is introduced. Tiny-sync features low complexity in network bandwidth, storage and processing, and achieves good accuracy in terrestrial networks. However, tiny-sync is time-consuming in UWA networks. We improve the traditional tiny-sync protocol by intensively scheduling message exchange to overcome high propagation latency problem. Simulation results show that improved tiny-sync has better performance in synchronization time than previous protocols, as well as retaining the advantage of small storage requirement in traditional tiny-sync.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132542397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-11-24DOI: 10.1109/OCEANS-TAIPEI.2014.6964327
S. Sato, S. Tabeta, M. Ozaki
A new cooling water system for power plant is proposed in which the cooling medium circulates in the closed duct system between the condenser and the heat exchanger installed at deep sea. This cooling system could improve power generation efficiency since deep sea water has lower temperature than surface water. It is also expected that the environmental impacts on the ocean surface layer will be greatly reduced because there is no warm water discharge. On the other hand, the influences of heat brought to the deep ocean have to be investigated. In the present study, the upwelling phenomena due to heat input in the bottom layer of the ocean with stratification and background current are investigated by hydraulic model experiments and numerical simulations. The upwelling height can be expressed by using non-dimensional parameters regarding the thermal input rate, the stratification gradient, and the velocity of background current.
{"title":"A fundamental study on upwelling due to heat input at deep sea","authors":"S. Sato, S. Tabeta, M. Ozaki","doi":"10.1109/OCEANS-TAIPEI.2014.6964327","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964327","url":null,"abstract":"A new cooling water system for power plant is proposed in which the cooling medium circulates in the closed duct system between the condenser and the heat exchanger installed at deep sea. This cooling system could improve power generation efficiency since deep sea water has lower temperature than surface water. It is also expected that the environmental impacts on the ocean surface layer will be greatly reduced because there is no warm water discharge. On the other hand, the influences of heat brought to the deep ocean have to be investigated. In the present study, the upwelling phenomena due to heat input in the bottom layer of the ocean with stratification and background current are investigated by hydraulic model experiments and numerical simulations. The upwelling height can be expressed by using non-dimensional parameters regarding the thermal input rate, the stratification gradient, and the velocity of background current.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125704909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-11-24DOI: 10.1109/OCEANS-TAIPEI.2014.6964530
Jianhua Wang, Yu Ping Wu, Yongsheng Yang, W. Gu, Jianying Mo
This paper discusses the sway of a spilled oil recovery apparatus mounted on the unmanned surface vehicle (USV) when it is lifted up off water surface. The dynamic model is established considering the pitch of the USV, and simulation experiment is conducted under the condition of no wind disturbance. The results show that the amplitude and frequency of the pitch are main factors influencing the sway of the oil recovery apparatus, and the effect of rope length on the sway is much smaller than amplitude and frequency of the pitch.
{"title":"Analysis on sway of spilled oil recovery apparatus lifted up from unmanned surface vehicle","authors":"Jianhua Wang, Yu Ping Wu, Yongsheng Yang, W. Gu, Jianying Mo","doi":"10.1109/OCEANS-TAIPEI.2014.6964530","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964530","url":null,"abstract":"This paper discusses the sway of a spilled oil recovery apparatus mounted on the unmanned surface vehicle (USV) when it is lifted up off water surface. The dynamic model is established considering the pitch of the USV, and simulation experiment is conducted under the condition of no wind disturbance. The results show that the amplitude and frequency of the pitch are main factors influencing the sway of the oil recovery apparatus, and the effect of rope length on the sway is much smaller than amplitude and frequency of the pitch.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116881093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-11-24DOI: 10.1109/OCEANS-TAIPEI.2014.6964335
Yaozhen Wu, Yixin Yang, Can Tao, Feng Tian, Long Yang
Feature vector extraction is measured as major step in development of underwater target recognition. To improve robustness of the performance of feature vector extraction, we proposed a novel approach for robust underwater target recognition applying the auditory cepstral coefficients (ACC) based on auditory filter and cubic-log compression instead of Mel filter and logarithmic compression in Mel-frequency cepstral coefficients (MFCC). Our experimental results show that the ACC feature represents considerably better than conventional acoustic features, and the ACC feature is used for underwater target recognition system to yield promising recognition performance.
{"title":"Robust underwater target recognition using auditory cepstral coefficients","authors":"Yaozhen Wu, Yixin Yang, Can Tao, Feng Tian, Long Yang","doi":"10.1109/OCEANS-TAIPEI.2014.6964335","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964335","url":null,"abstract":"Feature vector extraction is measured as major step in development of underwater target recognition. To improve robustness of the performance of feature vector extraction, we proposed a novel approach for robust underwater target recognition applying the auditory cepstral coefficients (ACC) based on auditory filter and cubic-log compression instead of Mel filter and logarithmic compression in Mel-frequency cepstral coefficients (MFCC). Our experimental results show that the ACC feature represents considerably better than conventional acoustic features, and the ACC feature is used for underwater target recognition system to yield promising recognition performance.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114281981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964556
S. Tully, D. Ingram
This paper presents preliminary results from turbulence modelling in channels. Identifying key characteristics of turbulence within tidal flows and providing a basis for further study of turbine specific turbulence behaviour. Numerical simulations have been performed using Code_Saturne [1], EDFs open source finite-volume code. Comparisons of Large Eddy Simulation and unsteady-averaged Navier Stokes methods for capturing the turbulence signatures present in empty channel flow are presented. Paying particular attention to resolved power spectral density distributions of turbulence. As well as vorticity isoplane analysis. Synthetic eddy inlet conditions [2] were used to model fully turbulent flow at the inlet. Results of numerical simulations of a test flume are presented using three turbulence modelling techniques - LES, Rij - ε SSG and k - ε. It is found that the k - ε model performed most poorly at resolving the turbulent eddies. Whilst the Rij - ε SSG model is proven to be a possible alternative to the more computationally expensive LES model when looking at large to mid scale turbulence. Analysis of viscosity isoplanes indicates that both the Rij - ε SSG and k - ε turbulence models dampened out large scale turbulence at a greater rate than the LES model - though a reasonably similar distribution of turbulent eddies still propagated downstream with the Rij - ε SSG model. Whilst the results from all three models could benefit from further mesh refinement the turbulent forces acting across a hypothetical turbine region is show to be anti-symmetric. This anti-symmetry across the rotor plane requires further study and inclusion in wake-mixing models used in tidal farm layout tools.
{"title":"Modelling tidal channels preliminary results in turbulence","authors":"S. Tully, D. Ingram","doi":"10.1109/OCEANS-TAIPEI.2014.6964556","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964556","url":null,"abstract":"This paper presents preliminary results from turbulence modelling in channels. Identifying key characteristics of turbulence within tidal flows and providing a basis for further study of turbine specific turbulence behaviour. Numerical simulations have been performed using Code_Saturne [1], EDFs open source finite-volume code. Comparisons of Large Eddy Simulation and unsteady-averaged Navier Stokes methods for capturing the turbulence signatures present in empty channel flow are presented. Paying particular attention to resolved power spectral density distributions of turbulence. As well as vorticity isoplane analysis. Synthetic eddy inlet conditions [2] were used to model fully turbulent flow at the inlet. Results of numerical simulations of a test flume are presented using three turbulence modelling techniques - LES, Rij - ε SSG and k - ε. It is found that the k - ε model performed most poorly at resolving the turbulent eddies. Whilst the Rij - ε SSG model is proven to be a possible alternative to the more computationally expensive LES model when looking at large to mid scale turbulence. Analysis of viscosity isoplanes indicates that both the Rij - ε SSG and k - ε turbulence models dampened out large scale turbulence at a greater rate than the LES model - though a reasonably similar distribution of turbulent eddies still propagated downstream with the Rij - ε SSG model. Whilst the results from all three models could benefit from further mesh refinement the turbulent forces acting across a hypothetical turbine region is show to be anti-symmetric. This anti-symmetry across the rotor plane requires further study and inclusion in wake-mixing models used in tidal farm layout tools.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123181538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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