The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)最新文献

{"title":"Physics-based and Machine learning predictions of maneuvering forces in unsteady inflow conditions","authors":"Rodrigo Vilumbrales Garcia, G. Weymouth, B. Ganapathisubramani","doi":"10.2218/marine2021.6832","DOIUrl":"https://doi.org/10.2218/marine2021.6832","url":null,"abstract":"Multi-vessel coordination and controlled maneuvering through upstream wakes is important to a wide range of marine applications; from surface ships to autonomous underwater vehicles. In this work we study the predictive performance of physics-based and machine-learning (ML) models for unsteady inflow maneuvering forces using tandem flapping foils as a model system. Two physics-based approaches, one following simple quasi-steady assumptions and another that modifies classical Theodorsen, are found to perform fairly well when there are only mild interactions with the upstream wake, with minimum error levels of around 6%. However, this error increases to 40% when there is strong wake interaction. Three ML models were trained and tested; a Long Short-Term Memory (LSTM) model, a Neural Ordinary Differential Equations (NODE) model, and a Sparse Identification of Nonlinear Dynamics (SINDy) approach. We find that all three models can match the low error of the physics-based for mild inflow unsteadiness and are capable of improving the predictions in the case of strong interactions, reducing the error levels below 20%. While these ML models require substantial training data and care in choosing their meta-parameters, their predictions do prove to be more reliable for a wider range of unsteadiness conditions as well as potentially still producing human-interpretable models (in the case of SINDy), making them an interesting research direction for further study.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132271620","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}

{"title":"Analysis of biomimetic stream energy device based on flapping foils","authors":"Iro Malefaki, D. Anevlavi, K. Belibassakis","doi":"10.2218/marine2021.6841","DOIUrl":"https://doi.org/10.2218/marine2021.6841","url":null,"abstract":". In this work, the performance of biomimetic device that consists of including a rotating, vertically mounted, biomimetic wing, supported by an arm linked at a pivot point on the mid-chord is evaluated using a numerical model is considered and results are presented concerning the performance. Activated by a controllable self-pitching motion, the system performs angular oscillations around the vertical axis in incoming flow. The performance of the above flapping-foil, biomimetic flow energy harvester, is calculated and the results are compared against experimental data. By systematical application of the model the power extraction and efficiency of the system is presented for various cases including different geometric, mechanical, and kinematic parameters, and the optimal performance of the system is determined. Also comparisons of the calculated performance are presented against predictions for other tidal energy devices, such as the stream energy converters based on the vortex-induced angular oscillations of a cylinder.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115643216","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}

{"title":"Wave calibration in numerical wave tanks using AI methods","authors":"C. Gillan, P. Schmitt, C. Finnegan","doi":"10.2218/marine2021.6826","DOIUrl":"https://doi.org/10.2218/marine2021.6826","url":null,"abstract":"Analytical solutions for numerical wavetanks are limited presently to a simple bathymetry and third order accuracy. Furthermore, tanks are generally characterised using linear transfer functions to relate the wavemaker forcing amplitude to wave elevation at a probe located in the wavetank. This paper reports on a numerical wavetank implemented using the OpenFOAM software package. The aim of the research is to train neural networks to represent non-linear transfer functions mapping a desired wave surface-elevation time-trace at a probe to the wavemaker input required to create it.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116709653","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}

{"title":"Numerical prediction of propeller induced hull pressure pulses using RANS and IDDES","authors":"M. Ge, U. Svennberg, R. Bensow","doi":"10.2218/marine2021.6860","DOIUrl":"https://doi.org/10.2218/marine2021.6860","url":null,"abstract":"","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123946848","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}

{"title":"Stability and transition of the wake of a hydrokinetic axial-flow turbine","authors":"A. Posa, R. Broglia","doi":"10.2218/marine2021.6797","DOIUrl":"https://doi.org/10.2218/marine2021.6797","url":null,"abstract":"A Large-Eddy Simulation study is reported on the wake generated by the rotor of an axial-flow hydrokinetic turbine. The resolution of the computational grid, composed of about 1.9 billion points, enabled us to capture in detail the phenomena of instability of the tip vortices, including long-wave and short-wave instabilities and mutual inductance. We found that these phenomena trigger the process of wake recovery, starting when the coherence of the tip vortices is lost. This allows the free-stream momentum to penetrate into the wake core via both radial inward flows and turbulent mixing.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125787149","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}

{"title":"Geometric Convolutional Neural Networks – A Journey to Surrogate Modelling of Maritime CFD","authors":"Asad Abbas, A. Rafiee, M. Haase, A. Malcolm","doi":"10.2218/marine2021.6838","DOIUrl":"https://doi.org/10.2218/marine2021.6838","url":null,"abstract":". Computational Fluid Dynamics (CFD) has become an indispensable tool in the field of engineering design evaluation and optimisation. Existing numerical simulation methods are computationally expensive, memory demanding and time-consuming, thus limiting design space exploration and forbid generative design. In order to overcome these challenges, we propose a deep learning based surrogate modeling in-lieu of CFD simulations. Our proposed framework can predict flow fields (e.g pressure field) on the surface of the geometry as well as any overall scalar parameters (e.g drag force) given a three-dimensional shape input. It can also provide uncertainty quantification over predictions. Finally, we demonstrate that our proposed surrogate modelling does not require pre-processing of the input geometry and also outperforms state-of-the-art models in prediction accuracy. When comparing a dataset on aerodynamic drag of car geometries, we show that our model reduced the error standard deviation by a factor of ≈ 2 . 5 compared to a Gaussian Process-based surrogate model.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130580166","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}

{"title":"Numerical and experimental investigation of the integrated system of floating wind and wave energy converters","authors":"Ling Wan","doi":"10.2218/marine2021.6776","DOIUrl":"https://doi.org/10.2218/marine2021.6776","url":null,"abstract":"","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127710390","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}

{"title":"CFD verification and validation of added resistance and seakeeping response in regular oblique waves with varying wave length","authors":"H. Mikkelsen, Yanlin Shao, Jens Honoré Walther","doi":"10.2218/marine2021.6786","DOIUrl":"https://doi.org/10.2218/marine2021.6786","url":null,"abstract":"The importance of CFD is increasing in marine hydrodynamics in studying seakeeping and added resistance of ships. While extensive numerical studies have been reported for various ships in head seas in the literature, much fewer CFD studies are found for oblique waves, which in practice is very important in, for instance, estimating required power and manoeuvrability of ships in realistic sea states. In this paper, the added resistance and motion responses for the KCS container ship in regular waves are studied and validated systematically for five wave headings and six wavelengths using CFD. The ship is free to heave, pitch, and roll. Implementations to the commercial CFD code are made to fix the yaw and surge motions. Extensive verification of the CFD model finds the estimated spatial and temporal discretization errors to be less than 5 %. Results of the verified CFD model are compared with up to three sets of experimental data sets, Potential Flow (PF) and existing CFD results from the literature. In general, the present CFD results show significantly better agreement with the experiments than previously published CFD results. The agreement between the present CFD model and experiments is better for the headings, where the uncertainties of the experiments are smallest. Present CFD results confirm previous published numerical findings that the experimental roll motion is excessive for the 45 ◦ heading. and validation of seakeeping responses and added resistance of the KCS container ship in regular oblique waves by using a CFD approach with turbulence modelling. Convergence studies of both the temporal and spatial discretization errors are presented. Discussions are made to determine affordable time steps and mesh sizes while to keep the discretization errors acceptable. The yaw and surge motions are constrained by user-implementations in the commercial software, which consist of additions of springs and concentrated forces/moment to cancel the fluid forces and moments. The mesh and time step convergence studies shows that the sum of the spatial and temporal discretization errors for an affordable calculation is less than 5 %, which is smaller than the average standard deviation of the experiments by (Sanada et al., 2021). A study of","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130794902","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}

{"title":"Numerical studies of offshore performance of floating protective barriers in waves and currents","authors":"A. Knysh, John W. Coyle, J. Decew, Andrew Drach, M. Swift, I. Tsukrov","doi":"10.2218/marine2021.6844","DOIUrl":"https://doi.org/10.2218/marine2021.6844","url":null,"abstract":"Finite element modeling was applied to evaluate the performance of Triton® floating protective barrier designed by HALO Maritime Defense Systems (US) and used to provide essential protection to critical governmental, commercial, and private assets vulnerable to water-borne intrusion, such as liquefied natural gas terminals, tankers, etc. The numerical model created with Hydro-FE software was validated by physical tests and field deployment observations. Physical tests of a scaled barrier model were conducted in Chase Ocean Engineering Laboratory wave tank at the University of New Hampshire to measure response of the structure and its mooring to different single-frequency waves directed parallel and normal to the model. The field deployment of the full-scale barrier performed south-southwest of White Island, Isles of Shoals, New Hampshire, provided information on its dynamic behavior under monitored environmental conditions. Good correspondence between numerical, physical and field studies was observed. The validated numerical model of the barrier was then used to investigate its performance and seaworthiness in other current and wave conditions with different mooring pretension scenarios.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122845087","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}

{"title":"Analysis of a floating wave energy converter interaction with waves using the Overset framework","authors":"G. Barajas, Javier L. Lara, B. Di Paolo, I. Losada","doi":"10.2218/marine2021.6791","DOIUrl":"https://doi.org/10.2218/marine2021.6791","url":null,"abstract":". The aim of this work is to validate and analyze with the numerical model OpenFOAM, the nonlinear interaction of a WEC under regular waves using the Overset framework. Previous techniques, such as deforming grid approaches, present problems to handle large body motions when modelling wave-structure interactions. Therefore, by means of the Overset mesh technique, the interaction of a moored floating wave energy converter in free and moored decay tests and under regular waves are analyzed. Numerical results are compared with experimental data for validation and discussed. MooDy Library is used to compute the mooring restraints.","PeriodicalId":367395,"journal":{"name":"The 9th Conference on Computational Methods in Marine Engineering (Marine 2021)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124537126","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}