Jingyuan Wan, G. Yin, Shengnan Liu, M. Ong, Petter Moen
Glass reinforced plastic (GRP) subsea protection covers are often used to protect offshore pipelines, umbilicals and other important subsea structures from dropped objects released from offshore oil and gas and fishing activities. These covers are often subjected to waves. In the present study, flows around an oscillating GRP subsea cover and oscillatory flows around a stationary subsea cover are investigated using numerical simulations at three different KC numbers of 5, 11 and 20, which are representative for low, medium and large KC number regions. The simulations of flows around an oscillating subsea cover are used to compare with the experiments done by SINTEF Ocean (formerly MARINTEK) and validate the present numerical model. Two-dimensional (2D) simulations are carried out by solving the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations combined with the k-ω Shear Stress Transport (SST) turbulence model. It is found that the hydrodynamic forces for the two cases (flows around the oscillating cover and oscillatory flows around the stationary cover) are almost the same, which verifies that the experimental tests of subsea covers with forced motions can be used to study hydrodynamic forces on the stationary cover subjected to waves. The horizontal and vertical force coefficients and the surrounding flow fields around the covers are discussed.
玻璃钢(GRP)水下保护罩通常用于保护海上管道、脐带缆和其他重要的海底结构免受海上油气和捕鱼活动释放的掉落物的伤害。这些覆盖物经常受到波浪的影响。在本研究中，采用数值模拟的方法，研究了振荡GRP海底覆盖物周围的流动和静止海底覆盖物周围的流动，分别在KC值为5、11和20的3个不同的KC值下，分别代表了低、中、大KC值区域。通过与SINTEF Ocean(以前的MARINTEK)的实验进行比较，验证了目前的数值模型。通过求解非定常reynolds - average Navier-Stokes (URANS)方程并结合k-ω剪切应力输运(SST)湍流模型进行二维(2D)模拟。结果表明，两种情况下(绕振荡盖板流动和绕静止盖板流动)的水动力几乎相同，验证了水下盖板受强迫运动的实验试验可以用于研究波浪作用下静止盖板的水动力。讨论了盖板周围的水平、垂直力系数和流场。
{"title":"Numerical Simulations of Flows Around Subsea Cover","authors":"Jingyuan Wan, G. Yin, Shengnan Liu, M. Ong, Petter Moen","doi":"10.1115/omae2021-66757","DOIUrl":"https://doi.org/10.1115/omae2021-66757","url":null,"abstract":"\u0000 Glass reinforced plastic (GRP) subsea protection covers are often used to protect offshore pipelines, umbilicals and other important subsea structures from dropped objects released from offshore oil and gas and fishing activities. These covers are often subjected to waves. In the present study, flows around an oscillating GRP subsea cover and oscillatory flows around a stationary subsea cover are investigated using numerical simulations at three different KC numbers of 5, 11 and 20, which are representative for low, medium and large KC number regions. The simulations of flows around an oscillating subsea cover are used to compare with the experiments done by SINTEF Ocean (formerly MARINTEK) and validate the present numerical model. Two-dimensional (2D) simulations are carried out by solving the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations combined with the k-ω Shear Stress Transport (SST) turbulence model. It is found that the hydrodynamic forces for the two cases (flows around the oscillating cover and oscillatory flows around the stationary cover) are almost the same, which verifies that the experimental tests of subsea covers with forced motions can be used to study hydrodynamic forces on the stationary cover subjected to waves. The horizontal and vertical force coefficients and the surrounding flow fields around the covers are discussed.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"115 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90910441","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}
An application of cyber-physical testing to the empirical estimation of difference-frequency quadratic transfer functions is presented. As an alternative to today's procedure based on hydrodynamic tests with broad-banded or realistic (e.g., JONSWAP) wave spectra, tests in bichromatic waves are considered. The laboratory setup is the one developed by Sauder & Tahchiev (2020) that enables magnifying the sensitivity of the floater response to the low-frequency wave loading by adjusting the stiffness and damping parameters of a virtual soft mooring system. Bayesian experimental design is proposed to optimize the selection of the control variables (frequencies in the bichromatic wave and properties of the virtual mooring system) for a batch of cyber-physical tests. The experimental design algorithm is based on the recent work of Huan & Marzouk (2013). In a virtual yet realistic case study using an uncertain parametric quadratic transfer function, we demonstrate how the uncertainty of its describing parameters and other calibration parameters (low-frequency added mass and hydrodynamic damping) can be reduced. Results indicate that the proposed procedure has the potential for reducing experimental cost for calibration of hydrodynamic models.
{"title":"Bayesian Experimental Design of Cyber-Physical Tests for Hydrodynamic Model Calibration","authors":"G. Abbiati, T. Sauder","doi":"10.31224/osf.io/bxpr3","DOIUrl":"https://doi.org/10.31224/osf.io/bxpr3","url":null,"abstract":"An application of cyber-physical testing to the empirical estimation of difference-frequency quadratic transfer functions is presented. As an alternative to today's procedure based on hydrodynamic tests with broad-banded or realistic (e.g., JONSWAP) wave spectra, tests in bichromatic waves are considered. The laboratory setup is the one developed by Sauder & Tahchiev (2020) that enables magnifying the sensitivity of the floater response to the low-frequency wave loading by adjusting the stiffness and damping parameters of a virtual soft mooring system. Bayesian experimental design is proposed to optimize the selection of the control variables (frequencies in the bichromatic wave and properties of the virtual mooring system) for a batch of cyber-physical tests. The experimental design algorithm is based on the recent work of Huan & Marzouk (2013). In a virtual yet realistic case study using an uncertain parametric quadratic transfer function, we demonstrate how the uncertainty of its describing parameters and other calibration parameters (low-frequency added mass and hydrodynamic damping) can be reduced. Results indicate that the proposed procedure has the potential for reducing experimental cost for calibration of hydrodynamic models.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75681047","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}
The barge-type foundation with moonpool(s) is a promising type of platform for floating offshore wind turbines, since the moonpool(s) could improve the hydrodynamic performance at particular frequencies and reduce the costs of construction. In this paper, the horizontal mean drift force and yaw drift moment of a barge-type platform with four moonpools are numerically and experimentally investigated. Physical model tests are carried out in a wave tank, where a 2MW vertical-axis wind turbine is modelled in the 1:100 scale. By varying the rotating speed of the turbine and the mass of the blades, the gyroscopic effects due to turbine rotations on the mean drift forces are experimentally examined. The wave diffraction and radiation code WAMIT is used to carry out numerical analysis of wave drift force and moment. The experimental results indicate that the influence of the rotations of a vertical-axis wind turbine on the sway drift force is generally not very significant. The predictions by WAMIT are in reasonable agreement with the measured data. Numerical results demonstrate that the horizontal mean drift force and yaw drift moment at certain frequencies could be reduced by moonpool(s).
{"title":"Mean Wave Drift Force on a Barge-Type Floating Wind Turbine With Moonpools","authors":"L. Tan, T. Ikoma, Y. Aida, K. Masuda","doi":"10.1115/omae2021-62241","DOIUrl":"https://doi.org/10.1115/omae2021-62241","url":null,"abstract":"\u0000 The barge-type foundation with moonpool(s) is a promising type of platform for floating offshore wind turbines, since the moonpool(s) could improve the hydrodynamic performance at particular frequencies and reduce the costs of construction. In this paper, the horizontal mean drift force and yaw drift moment of a barge-type platform with four moonpools are numerically and experimentally investigated. Physical model tests are carried out in a wave tank, where a 2MW vertical-axis wind turbine is modelled in the 1:100 scale. By varying the rotating speed of the turbine and the mass of the blades, the gyroscopic effects due to turbine rotations on the mean drift forces are experimentally examined. The wave diffraction and radiation code WAMIT is used to carry out numerical analysis of wave drift force and moment. The experimental results indicate that the influence of the rotations of a vertical-axis wind turbine on the sway drift force is generally not very significant. The predictions by WAMIT are in reasonable agreement with the measured data. Numerical results demonstrate that the horizontal mean drift force and yaw drift moment at certain frequencies could be reduced by moonpool(s).","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81599137","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}
The produced fluids in a subsea field development can be transported from the subsea well to a floating production unit using pipelines where they are thereafter offloaded to a tanker (surface ship). The flow direction is reversed in the case of CO2 injection into the subsea well. This CO2 offloading process is highly dependent on the weather conditions and it cannot be performed when the conditions are severe. Furthermore, subsea pipeline systems can be expensive to install and maintain. In the present study, a novel subsea freight-glider system is proposed as a suitable, cost-effective, energy-efficient alternative to tanker ships and pipelines. The proposed vehicle is autonomous, 50 m long, has a 1500 DWT displacement, and can carry approximately 800 tons of cargo. The subsea freight-glider uses variable-buoyancy propulsion instead of traditional propellers/thrusters. It changes ballast to provide positive and negative net buoyancy which allows it to glide subsea through the water using hydrodynamic wings. This is an extremely energy efficient way of transporting large amounts of cargo over medium/long distances. Since the subsea freight-glider operates underneath the sea surface, it is not affected by wind and waves and can operate in any weather condition. Furthermore, subsea fields that are not large enough to justify the installation of subsea pipelines can still be developed. Even though the subsea freight-glider is proposed as a vehicle for liquid CO2 transport, it can also transport different types of cargo such as hydrocarbons, injection fluids and gasses, and even carry electrical power using batteries.
{"title":"A Conceptual Large Autonomous Subsea Freight-Glider for Liquid CO2 Transportation","authors":"Y. Xing","doi":"10.1115/omae2021-61924","DOIUrl":"https://doi.org/10.1115/omae2021-61924","url":null,"abstract":"\u0000 The produced fluids in a subsea field development can be transported from the subsea well to a floating production unit using pipelines where they are thereafter offloaded to a tanker (surface ship). The flow direction is reversed in the case of CO2 injection into the subsea well. This CO2 offloading process is highly dependent on the weather conditions and it cannot be performed when the conditions are severe. Furthermore, subsea pipeline systems can be expensive to install and maintain. In the present study, a novel subsea freight-glider system is proposed as a suitable, cost-effective, energy-efficient alternative to tanker ships and pipelines. The proposed vehicle is autonomous, 50 m long, has a 1500 DWT displacement, and can carry approximately 800 tons of cargo. The subsea freight-glider uses variable-buoyancy propulsion instead of traditional propellers/thrusters. It changes ballast to provide positive and negative net buoyancy which allows it to glide subsea through the water using hydrodynamic wings. This is an extremely energy efficient way of transporting large amounts of cargo over medium/long distances. Since the subsea freight-glider operates underneath the sea surface, it is not affected by wind and waves and can operate in any weather condition. Furthermore, subsea fields that are not large enough to justify the installation of subsea pipelines can still be developed. Even though the subsea freight-glider is proposed as a vehicle for liquid CO2 transport, it can also transport different types of cargo such as hydrocarbons, injection fluids and gasses, and even carry electrical power using batteries.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73144352","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}
Accurately determining water surface elevation and wave shapes in the hydraulic laboratory is critical for experimental research and physical understanding of ocean waves. Existing technologies such as wave gauges cannot capture the continuous wave profile across both space and time. This poses an issue, as nonlinear wave characteristics vary as a function of position and cannot be fully described using such point measurements. Furthermore, wave gauges are intrusive to the flow field. Alternative single-camera methods can’t capture wave characteristics in a large field-of-view properly without sacrificing resolution. In this paper, the authors propose an easy-to-use, low-cost method for measuring wave height and shape along the length of the flume over time. The method utilizes stitching of multiple web-cameras and the application of a Canny-based edge detection algorithm with experimentally determined thresholds and additional filters for maximum robustness and efficacy. Additionally, distortion correction is implemented in a computationally efficient manner. Video is acquired by three Logitech C920 PRO HD cameras recording at a resolution of 1280 × 720 at 24fps. The wave generator can generate waves with frequency between 0.1Hz and 1Hz. The experimental results show that wave height measurements can be obtained with a maximum resolution of 0.83mm with a relative error of ±1.5% when compared with a reference wave gauge measurement. This work demonstrates the ability to arbitrarily extend the horizontal field-of-view while providing more accurate measurement results.
{"title":"A Low-Cost Modular Image-Based Approach to Characterize Large-Field Wave Shapes in Glass Wave Flume","authors":"Shuang-xi Fu, M. Vronsky, Mohammad-Reza Alam","doi":"10.1115/omae2021-61864","DOIUrl":"https://doi.org/10.1115/omae2021-61864","url":null,"abstract":"\u0000 Accurately determining water surface elevation and wave shapes in the hydraulic laboratory is critical for experimental research and physical understanding of ocean waves. Existing technologies such as wave gauges cannot capture the continuous wave profile across both space and time. This poses an issue, as nonlinear wave characteristics vary as a function of position and cannot be fully described using such point measurements. Furthermore, wave gauges are intrusive to the flow field. Alternative single-camera methods can’t capture wave characteristics in a large field-of-view properly without sacrificing resolution. In this paper, the authors propose an easy-to-use, low-cost method for measuring wave height and shape along the length of the flume over time. The method utilizes stitching of multiple web-cameras and the application of a Canny-based edge detection algorithm with experimentally determined thresholds and additional filters for maximum robustness and efficacy. Additionally, distortion correction is implemented in a computationally efficient manner. Video is acquired by three Logitech C920 PRO HD cameras recording at a resolution of 1280 × 720 at 24fps. The wave generator can generate waves with frequency between 0.1Hz and 1Hz. The experimental results show that wave height measurements can be obtained with a maximum resolution of 0.83mm with a relative error of ±1.5% when compared with a reference wave gauge measurement. This work demonstrates the ability to arbitrarily extend the horizontal field-of-view while providing more accurate measurement results.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"81 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73376214","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}
This paper presents a Combined Method for the calculation of propeller forces in inhomogeneous inflow. It consists of an extended Goldstein approach based on Lifting Line Theory and a Vortex Lattice Method. After a brief overview of both methods is given, the coupling strategy is described and the additional modifications are explained. A correction factor accounting for the vortex which develops under a separated and later reattached flow on the suction side of the propeller blade is implemented as the first modification. Further, the Lamb-Oseen vortex model is used for the vortices in the free vortex system of the propeller. Finally, some results achieved with the described method are presented and compared to measured values.
{"title":"A Combined Vortex Lattice Lifting Line Method for Unsteady Propeller Calculations","authors":"Andreas Büsken, S. Krüger","doi":"10.1115/omae2021-61807","DOIUrl":"https://doi.org/10.1115/omae2021-61807","url":null,"abstract":"\u0000 This paper presents a Combined Method for the calculation of propeller forces in inhomogeneous inflow. It consists of an extended Goldstein approach based on Lifting Line Theory and a Vortex Lattice Method. After a brief overview of both methods is given, the coupling strategy is described and the additional modifications are explained. A correction factor accounting for the vortex which develops under a separated and later reattached flow on the suction side of the propeller blade is implemented as the first modification. Further, the Lamb-Oseen vortex model is used for the vortices in the free vortex system of the propeller. Finally, some results achieved with the described method are presented and compared to measured values.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77806681","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}
The benchmark experiment research for the maneuverability of a small-scaled ship model is critical for investigating the scaled effect on the maneuvering hydrodynamic derivatives, and validating the CFD technology. Till now, there is little research on the benchmark study and uncertainty analysis for the small-scaled ship which is frequently used in the Circulating Water Channel (CWC). Therefore, an experimental study of the planar motion mechanism (PMM) tests is performed in the CWC of the SJTU. The PMM tests performed in the CWC can avoid some disadvantages of those in the towing tank, such as the limitations on the acquisition time and frequency due to the size of the towing tank, interference of the carriage on the signal acquisition. In addition, the flow field visualization for the tests in the CWC is easier to achieve compared with the experiments in the towing tank, which helps the scholars to understand the characteristic of the wake field during maneuvers. The benchmark ship is the KVLCC2 with a scaled ratio of 1/128.77. The hull forces are recorded and processed to obtain the maneuvering hydrodynamic derivatives. To assess the quality of the acquired data, randomness analysis, stationarity analysis, normality analysis, and statistical convergence are performed for the PMM tests in the CWC for the first time. Finally, the uncertainty analysis (UA) method for the PMM tests performed in the CWC is also developed.
{"title":"Benchmark Study and Uncertainty Assessment of Planar Motion Mechanism Tests on KVLCC2 in a Circulating Water Channel","authors":"Chengqian Ma, N. Ma, X. Gu","doi":"10.1115/omae2021-62671","DOIUrl":"https://doi.org/10.1115/omae2021-62671","url":null,"abstract":"\u0000 The benchmark experiment research for the maneuverability of a small-scaled ship model is critical for investigating the scaled effect on the maneuvering hydrodynamic derivatives, and validating the CFD technology. Till now, there is little research on the benchmark study and uncertainty analysis for the small-scaled ship which is frequently used in the Circulating Water Channel (CWC). Therefore, an experimental study of the planar motion mechanism (PMM) tests is performed in the CWC of the SJTU. The PMM tests performed in the CWC can avoid some disadvantages of those in the towing tank, such as the limitations on the acquisition time and frequency due to the size of the towing tank, interference of the carriage on the signal acquisition. In addition, the flow field visualization for the tests in the CWC is easier to achieve compared with the experiments in the towing tank, which helps the scholars to understand the characteristic of the wake field during maneuvers. The benchmark ship is the KVLCC2 with a scaled ratio of 1/128.77. The hull forces are recorded and processed to obtain the maneuvering hydrodynamic derivatives. To assess the quality of the acquired data, randomness analysis, stationarity analysis, normality analysis, and statistical convergence are performed for the PMM tests in the CWC for the first time. Finally, the uncertainty analysis (UA) method for the PMM tests performed in the CWC is also developed.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"140 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88730448","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}
Z. Y. Tay, J. Hadi, D. Konovessis, De Jin Loh, David Kong Hong Tan, Xiaobo Chen
This paper presents the analysis to reduce carbon emission from tugboat operations by utilizing a proposed unsupervised machine learning operational scoring system. The time-series analysis is performed by transforming data into a common domain for clustering. The data are collected from a tugboat to investigate the correlation between environmental and location data with fuel consumption to achieve fuel efficiency. The relevant parameters that influence the fuel consumption of the tugboat, such as fuel consumption, vessel route, vessel speed and wind metrics are collected from sensors installed onboard the ship and data provider to monitor and to gauge the vessel’s performance. The raw readings are conditioned (data cleaning and data pre-processing) before transformation to Score Dataset: the Raw mass-flowrate readings are cleaned by using the Haar wavelet; the wind raw reading is converted to wind effect data; the Location data is converted to vessel speed data. Together, they form a Score Dataset by applying the time series K-means clustering. The subsequent unsupervised learning identifies the activity labels that describe qualitatively the operations of the vessels and are obtained by using the non-time series K-mean clustering. By using the Hidden Markov Model approach, this paper attempts to explain the stochastic correlation among parameters explained earlier. The correlation is the information of newly discovered knowledge in terms of likelihood matrices, also known as the knowledge base (KB). The KB may be consumed to perform predictions. Hence, it is possible to suggest the optimal ship operation, i.e., speed that produces the optimum fuel consumption. The Score Dataset and clustering that are produced in this paper could also be used in the Artificial Neural Network for future work.
{"title":"Efficient Harbor Craft Monitoring System: Time-Series Data Analytics and Machine Learning Tools to Achieve Fuel Efficiency by Operational Scoring System","authors":"Z. Y. Tay, J. Hadi, D. Konovessis, De Jin Loh, David Kong Hong Tan, Xiaobo Chen","doi":"10.1115/omae2021-62658","DOIUrl":"https://doi.org/10.1115/omae2021-62658","url":null,"abstract":"\u0000 This paper presents the analysis to reduce carbon emission from tugboat operations by utilizing a proposed unsupervised machine learning operational scoring system. The time-series analysis is performed by transforming data into a common domain for clustering. The data are collected from a tugboat to investigate the correlation between environmental and location data with fuel consumption to achieve fuel efficiency. The relevant parameters that influence the fuel consumption of the tugboat, such as fuel consumption, vessel route, vessel speed and wind metrics are collected from sensors installed onboard the ship and data provider to monitor and to gauge the vessel’s performance. The raw readings are conditioned (data cleaning and data pre-processing) before transformation to Score Dataset: the Raw mass-flowrate readings are cleaned by using the Haar wavelet; the wind raw reading is converted to wind effect data; the Location data is converted to vessel speed data. Together, they form a Score Dataset by applying the time series K-means clustering. The subsequent unsupervised learning identifies the activity labels that describe qualitatively the operations of the vessels and are obtained by using the non-time series K-mean clustering. By using the Hidden Markov Model approach, this paper attempts to explain the stochastic correlation among parameters explained earlier. The correlation is the information of newly discovered knowledge in terms of likelihood matrices, also known as the knowledge base (KB). The KB may be consumed to perform predictions. Hence, it is possible to suggest the optimal ship operation, i.e., speed that produces the optimum fuel consumption. The Score Dataset and clustering that are produced in this paper could also be used in the Artificial Neural Network for future work.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87265419","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 hydrodynamic digital twin of vessel can be used to replicate the behaviour and response of the vessel in a virtual environment. In this paper, a real-time simulation model (RTSM) for an azimuth stern-drive (ASD) tug has been developed for simulating the hydrodynamic performance of the vessel under a range of environmental conditions. Based on the framework of a 4-DoF MMG manoeuvring model, the RTSM comprises manoeuvring, propulsion and environmental loads which are parameterised using numerical results from a combination of computational fluid dynamics (CFD) modelling work, including virtual planar motion mechanism (vPMM), seakeeping analysis, wind drag prediction and propulsion modelling. The RTSM is used to demonstrate the manoeuvrability of the vessel in calm water and under external loads from waves, winds and currents.
{"title":"Development of a Real-Time Simulation Model for an ASD Tug","authors":"Yuting Jin, Yingying Zheng, L. Yiew, A. Magee","doi":"10.1115/omae2021-63052","DOIUrl":"https://doi.org/10.1115/omae2021-63052","url":null,"abstract":"\u0000 A hydrodynamic digital twin of vessel can be used to replicate the behaviour and response of the vessel in a virtual environment. In this paper, a real-time simulation model (RTSM) for an azimuth stern-drive (ASD) tug has been developed for simulating the hydrodynamic performance of the vessel under a range of environmental conditions. Based on the framework of a 4-DoF MMG manoeuvring model, the RTSM comprises manoeuvring, propulsion and environmental loads which are parameterised using numerical results from a combination of computational fluid dynamics (CFD) modelling work, including virtual planar motion mechanism (vPMM), seakeeping analysis, wind drag prediction and propulsion modelling. The RTSM is used to demonstrate the manoeuvrability of the vessel in calm water and under external loads from waves, winds and currents.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90145479","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}
In this paper, the CFD framework REEF3D is utilized to investigate the hydrodynamics of a large offshore fish farm in waves. The solver consists of a rigid body dynamics solver for the frame structure coupled to a fluid solver including the shielding effects of the nets. The solver and the grid independence are validated using a 2D numerical wave tank, a free decay test, and a study of the wave loads on a rigid net panel. Then, the effects of regular wave parameters, the thickness of the vertical outer columns of the structure, and varies aspect ratios on the loads, response and maximum mooring tensions are investigated. It is concluded that the response is sensitive to the wave period rather than the wave height and that the net system accounts for about 30% of the total drag but does not influence the structural response to a larger extend. The effect of the aspect ratio on the hydrodynamics is more distinct than that of the frame thickness especially. Thus, the first step towards a systemic evaluation of the importance of different structural parts of an offshore fish cage for the expected responses is presented in this paper.
{"title":"A Numerical Study of the Hydrodynamics of an Offshore Fish Farm Using REEF3D","authors":"G. Wang, T. Martin, Liu-yi Huang, H. Bihs","doi":"10.1115/omae2021-62012","DOIUrl":"https://doi.org/10.1115/omae2021-62012","url":null,"abstract":"\u0000 In this paper, the CFD framework REEF3D is utilized to investigate the hydrodynamics of a large offshore fish farm in waves. The solver consists of a rigid body dynamics solver for the frame structure coupled to a fluid solver including the shielding effects of the nets. The solver and the grid independence are validated using a 2D numerical wave tank, a free decay test, and a study of the wave loads on a rigid net panel. Then, the effects of regular wave parameters, the thickness of the vertical outer columns of the structure, and varies aspect ratios on the loads, response and maximum mooring tensions are investigated. It is concluded that the response is sensitive to the wave period rather than the wave height and that the net system accounts for about 30% of the total drag but does not influence the structural response to a larger extend. The effect of the aspect ratio on the hydrodynamics is more distinct than that of the frame thickness especially. Thus, the first step towards a systemic evaluation of the importance of different structural parts of an offshore fish cage for the expected responses is presented in this paper.","PeriodicalId":23784,"journal":{"name":"Volume 6: Ocean Engineering","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80701275","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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