In head waves, water jet impacts due to run up can occur as a result of the structural configuration of some floating structures, reducing workability. Wave attenuation near the floater may reduce the risk of water jet impacts. This paper presents a numerical study of the performance and attenuation mechanisms of various plate type fixed free surface breakwaters and their ability to prevent water jet impacts on adjacent structures. Simulations are performed in two dimensions with a numerical method based on the Navier–Stokes equations in the presence of a free surface. The breakwater models are evaluated in two irregular sea states in terms of wave transmission, reflection and energy dissipation and by their ability to reduce water jets impacts on adjacent structures. A 60 degree inclined plate is found to induce a large wave energy reduction, little wave transmission and reflection and to experience little wave loading while effectively reducing water jet impacts.
{"title":"Force and water jet impact reduction on adjacent structures by means of free surface breakwaters","authors":"K.J. Holkema, C. Aalbers, P. R. Wellens","doi":"10.3233/isp-230012","DOIUrl":"https://doi.org/10.3233/isp-230012","url":null,"abstract":"In head waves, water jet impacts due to run up can occur as a result of the structural configuration of some floating structures, reducing workability. Wave attenuation near the floater may reduce the risk of water jet impacts. This paper presents a numerical study of the performance and attenuation mechanisms of various plate type fixed free surface breakwaters and their ability to prevent water jet impacts on adjacent structures. Simulations are performed in two dimensions with a numerical method based on the Navier–Stokes equations in the presence of a free surface. The breakwater models are evaluated in two irregular sea states in terms of wave transmission, reflection and energy dissipation and by their ability to reduce water jets impacts on adjacent structures. A 60 degree inclined plate is found to induce a large wave energy reduction, little wave transmission and reflection and to experience little wave loading while effectively reducing water jet impacts.","PeriodicalId":45800,"journal":{"name":"International Shipbuilding Progress","volume":"2 3","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138944703","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}
Robert Wenink, M. van der Eijk, Neil Yorke-Smith, Peter Wellens
Surrogate modelling techniques such as Kriging are a popular means for cheaply emulating the response of expensive Computational Fluid Dynamics (CFD) simulations. These surrogate models are often used for exploring a parameterised design space and identifying optimal designs. Multi-fidelity Kriging extends the methodology to incorporate data of variable accuracy and costs to create a more effective surrogate. This work recognises that the grid convergence property of CFD solvers is currently an unused source of information and presents a novel method that, by leveraging the data structure implied by grid convergence, could further improve the performance of the surrogate model and the corresponding optimisation process. Grid convergence states that the simulation solution converges to the true simulation solution as the numerical grid is refined. The proposed method is tested with realistic multi-fidelity data acquired with CFD simulations. The performance of the surrogate model is comparable to an existing method, and likely more robust. More research is needed to explore the full potential of the proposed method. Code has been made available online at https://github.com/robertwenink/MFK-Extrapolation.
{"title":"Multi-fidelity Kriging extrapolation together with CFD for the design of the cross-section of a falling lifeboat","authors":"Robert Wenink, M. van der Eijk, Neil Yorke-Smith, Peter Wellens","doi":"10.3233/isp-230013","DOIUrl":"https://doi.org/10.3233/isp-230013","url":null,"abstract":"Surrogate modelling techniques such as Kriging are a popular means for cheaply emulating the response of expensive Computational Fluid Dynamics (CFD) simulations. These surrogate models are often used for exploring a parameterised design space and identifying optimal designs. Multi-fidelity Kriging extends the methodology to incorporate data of variable accuracy and costs to create a more effective surrogate. This work recognises that the grid convergence property of CFD solvers is currently an unused source of information and presents a novel method that, by leveraging the data structure implied by grid convergence, could further improve the performance of the surrogate model and the corresponding optimisation process. Grid convergence states that the simulation solution converges to the true simulation solution as the numerical grid is refined. The proposed method is tested with realistic multi-fidelity data acquired with CFD simulations. The performance of the surrogate model is comparable to an existing method, and likely more robust. More research is needed to explore the full potential of the proposed method. Code has been made available online at https://github.com/robertwenink/MFK-Extrapolation.","PeriodicalId":45800,"journal":{"name":"International Shipbuilding Progress","volume":"11 5","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138945024","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 colonization of barnacles on surfaces has detrimental effects on shipping, leisure vessels, heat exchangers, oceanographic sensors, and aquaculture systems. One strategy for avoiding barnacle colonization on surfaces is to utilize surface wettability. Silicone-incorporated diamond-like carbon (Si-DLC) has high hardness and a low friction coefficient, and an increase in the incorporation of Si leads to hydrophobicity. By contrast, oxygen plasma treatment produces hydrophilicity in Si-DLC films. The improved surface wettability of Si-DLC may reduce barnacle colonization. However, few studies have been conducted on barnacle larval settlement in relation to Si-DLC films. The aim of this study is to evaluate barnacle larval settlement on Si-DLC films and on oxygen-plasma-treated Si-DLC films. Si-DLC films were prepared by radio-frequency plasma-enhanced chemical vapor deposition and treated with oxygen plasma. The films were characterized using Raman spectroscopy and X-ray photoelectron spectroscopy. Contact angles of the films were measured to evaluate their hydrophobicity. Barnacle cyprid larva settlement was observed on the Si-DLC and oxygen-plasma-treated Si-DLC films. The contact angle of the Si-DLC-0% film was 69.9 ± 3 . 3 ∘ and increased with Si incorporation. Following oxygen plasma treatment, the contact angle of the Si-DLC-0% films decreased to 10.9 ± 4 . 4 ∘ and gradually increased with Si incorporation. The barnacle cyprid larval settlement ratio for the non-coated stainless plate was 36.4%, whereas that of the DLC films was 15.0%, which decreased with Si incorporation. Following oxygen plasma treatment, the ratio of barnacle cyprid larval settlement in Si-DLC films was lower than for the Si-DLC films. The Si-DLC film was effective in avoiding barnacle adhesion, whereas the oxygen-plasma-treated Si-DLC was even more effective. This study demonstrated the feasibility of Si-DLC for antifouling against barnacles.
{"title":"Effects of surface wettability of silicon-incorporated diamond-like carbon films on barnacle larval settlement","authors":"K. Ozeki, S. Nakahara","doi":"10.3233/isp-220008","DOIUrl":"https://doi.org/10.3233/isp-220008","url":null,"abstract":"The colonization of barnacles on surfaces has detrimental effects on shipping, leisure vessels, heat exchangers, oceanographic sensors, and aquaculture systems. One strategy for avoiding barnacle colonization on surfaces is to utilize surface wettability. Silicone-incorporated diamond-like carbon (Si-DLC) has high hardness and a low friction coefficient, and an increase in the incorporation of Si leads to hydrophobicity. By contrast, oxygen plasma treatment produces hydrophilicity in Si-DLC films. The improved surface wettability of Si-DLC may reduce barnacle colonization. However, few studies have been conducted on barnacle larval settlement in relation to Si-DLC films. The aim of this study is to evaluate barnacle larval settlement on Si-DLC films and on oxygen-plasma-treated Si-DLC films. Si-DLC films were prepared by radio-frequency plasma-enhanced chemical vapor deposition and treated with oxygen plasma. The films were characterized using Raman spectroscopy and X-ray photoelectron spectroscopy. Contact angles of the films were measured to evaluate their hydrophobicity. Barnacle cyprid larva settlement was observed on the Si-DLC and oxygen-plasma-treated Si-DLC films. The contact angle of the Si-DLC-0% film was 69.9 ± 3 . 3 ∘ and increased with Si incorporation. Following oxygen plasma treatment, the contact angle of the Si-DLC-0% films decreased to 10.9 ± 4 . 4 ∘ and gradually increased with Si incorporation. The barnacle cyprid larval settlement ratio for the non-coated stainless plate was 36.4%, whereas that of the DLC films was 15.0%, which decreased with Si incorporation. Following oxygen plasma treatment, the ratio of barnacle cyprid larval settlement in Si-DLC films was lower than for the Si-DLC films. The Si-DLC film was effective in avoiding barnacle adhesion, whereas the oxygen-plasma-treated Si-DLC was even more effective. This study demonstrated the feasibility of Si-DLC for antifouling against barnacles.","PeriodicalId":45800,"journal":{"name":"International Shipbuilding Progress","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44583608","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}
Trim optimization improves the energy efficiency of ships, thus reducing operational costs and emissions; however, trim tables are only available for a limited number of ships. There is thus a desire to develop additional, more accurate trim tables without the need for expensive model testing. The objective of this research was to develop a method to decrease fuel consumption by trim optimization, by a dynamic shaft power estimation model based on available operational data. A method that uses noon report data and a grey-box modelling approach is proposed. The grey box model consists of a multi-layer feedforward neural network to estimate the required shaft power, using operational parameters and an initial estimate of the required shaft power. A case study is presented for a modern chemical tanker and sea trials have been conducted to validate the results. The method provides correct trim advice for full load conditions; however, the magnitude of the effect is smaller compared to sea trial results. The model is able to estimate the required power with an average accuracy of over 6% for a random subset of the noon report data. Due to challenges inherent to noon reports as a data source, the actual effect of trim and speed have a bigger magnitude than the extracted trend.
{"title":"A Grey-box model approach using noon report data for trim optimization","authors":"Robert H. Zwart, Jordi Bogaard, A. Kana","doi":"10.3233/isp-220009","DOIUrl":"https://doi.org/10.3233/isp-220009","url":null,"abstract":"Trim optimization improves the energy efficiency of ships, thus reducing operational costs and emissions; however, trim tables are only available for a limited number of ships. There is thus a desire to develop additional, more accurate trim tables without the need for expensive model testing. The objective of this research was to develop a method to decrease fuel consumption by trim optimization, by a dynamic shaft power estimation model based on available operational data. A method that uses noon report data and a grey-box modelling approach is proposed. The grey box model consists of a multi-layer feedforward neural network to estimate the required shaft power, using operational parameters and an initial estimate of the required shaft power. A case study is presented for a modern chemical tanker and sea trials have been conducted to validate the results. The method provides correct trim advice for full load conditions; however, the magnitude of the effect is smaller compared to sea trial results. The model is able to estimate the required power with an average accuracy of over 6% for a random subset of the noon report data. Due to challenges inherent to noon reports as a data source, the actual effect of trim and speed have a bigger magnitude than the extracted trend.","PeriodicalId":45800,"journal":{"name":"International Shipbuilding Progress","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44146923","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}
Jochem de Kwant, R. Hekkenberg, Apostolos Souflis-Rigas, A. Kana
This article examines the potential implications of using iron powder as an alternative fuel on the design and performance of container ships. Iron powder is a relatively new alternative energy carrier and one in which little research has been done into the application on-board vessels as part of the maritime energy transition. The key benefits of iron powder are that it is a circular energy carrier and the combustion process emits no greenhouse gases. Transitioning to iron powder is expected to have far reaching implications for the design and performance of ships. Thus, this paper aims to perform the first study assessing the potential of this concept applied to container ships. To do so, a preliminary design space was explored with a custom parametric design model developed to generate preliminary designs of iron fuelled container ships as a function of the operational profile. Using this parametric design model, it was identified that iron fuelled container ships are weight limited, unlike conventionally fuelled container vessels. Furthermore, iron fuelled container ships are best suited for short voyages at low cruising speed. For these voyages, it was concluded that iron fuelled ships are economically feasible; however, other alternative marine fuels are likely more profitable than iron due to the low efficiency of iron fuelled ships and the high cost of iron per unit energy.
{"title":"Exploring the potential of iron powder as fuel on the design and performance of container ships","authors":"Jochem de Kwant, R. Hekkenberg, Apostolos Souflis-Rigas, A. Kana","doi":"10.3233/isp-220012","DOIUrl":"https://doi.org/10.3233/isp-220012","url":null,"abstract":"This article examines the potential implications of using iron powder as an alternative fuel on the design and performance of container ships. Iron powder is a relatively new alternative energy carrier and one in which little research has been done into the application on-board vessels as part of the maritime energy transition. The key benefits of iron powder are that it is a circular energy carrier and the combustion process emits no greenhouse gases. Transitioning to iron powder is expected to have far reaching implications for the design and performance of ships. Thus, this paper aims to perform the first study assessing the potential of this concept applied to container ships. To do so, a preliminary design space was explored with a custom parametric design model developed to generate preliminary designs of iron fuelled container ships as a function of the operational profile. Using this parametric design model, it was identified that iron fuelled container ships are weight limited, unlike conventionally fuelled container vessels. Furthermore, iron fuelled container ships are best suited for short voyages at low cruising speed. For these voyages, it was concluded that iron fuelled ships are economically feasible; however, other alternative marine fuels are likely more profitable than iron due to the low efficiency of iron fuelled ships and the high cost of iron per unit energy.","PeriodicalId":45800,"journal":{"name":"International Shipbuilding Progress","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44585063","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 two-dimensional (2D) boundary element method is developed for the rapid assessment of the hydrodynamic performance of floating structures in waves. The boundary element method is based on potential flow and has panels along all boundaries of the fluid domain – not only along the boundary of the floater – to make the extension to second order feasible. Panels along all boundaries requires the development of generating absorbing boundary conditions for use at radiation boundaries to send incident waves into the domain while absorbing waves originating from the floating body at the same boundary, at the same time. The model is verified by means of conservation of energy of a heaving wave energy converter, and by means of the propagation of second-order waves. The performance in terms of conservation of energy with 12 panels per wave length is good, the generating absorbing boundary condition works according to expectation and the second-order wave propagation corresponds to theory.
{"title":"A two-dimensional boundary element method with generating absorbing boundary condition for floating bodies of arbitrary shape in the frequency domain","authors":"Maarten Gabriel, P. Wellens","doi":"10.3233/isp-210007","DOIUrl":"https://doi.org/10.3233/isp-210007","url":null,"abstract":"A two-dimensional (2D) boundary element method is developed for the rapid assessment of the hydrodynamic performance of floating structures in waves. The boundary element method is based on potential flow and has panels along all boundaries of the fluid domain – not only along the boundary of the floater – to make the extension to second order feasible. Panels along all boundaries requires the development of generating absorbing boundary conditions for use at radiation boundaries to send incident waves into the domain while absorbing waves originating from the floating body at the same boundary, at the same time. The model is verified by means of conservation of energy of a heaving wave energy converter, and by means of the propagation of second-order waves. The performance in terms of conservation of energy with 12 panels per wave length is good, the generating absorbing boundary condition works according to expectation and the second-order wave propagation corresponds to theory.","PeriodicalId":45800,"journal":{"name":"International Shipbuilding Progress","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43830599","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}
Wu Hao, Lu Cong Hong, Liu Qiang, Yu Xin, Fan Wei, Peng Bi Ye
Background: The green ship technologies are gaining in importance in diverse areas of ship design. Objective: To explore the energy-saving and environmentally friendly ship during the primary ship designs stage. Methods: A hull form optimization method based on the full parametric modeling is proposed, in which the Computational Fluid Dynamic (CFD) analysis is integrated, and the algorithms of Sobol and NSGA-II are used. Taking a 674 m3 single trawler as an example, the full parametric modeling of forebody hull form is adopted by employing an F-spline curve with the software CAESES and the total resistance of the full-scale ship is computed by the integrated software SHIPFLOW numerically. Results: It is proved that the presented optimization method can engage well in the automation process of the hull form design under the constraints of displacement and longitudinal center of buoyancy. Compared with the initial hull form, the total resistance of the optimal ship at the design speed of 11.5 kn decreases 12.2%. Conclusions: It indicates that the proposed method of hull form optimization based on full parametric modeling proposed in this paper has better engineering applicability and broad application prospect in practical ship design practices.
{"title":"Hydrodynamic hull form optimization of a single trawler based on full parametric modeling","authors":"Wu Hao, Lu Cong Hong, Liu Qiang, Yu Xin, Fan Wei, Peng Bi Ye","doi":"10.3233/isp-220006","DOIUrl":"https://doi.org/10.3233/isp-220006","url":null,"abstract":"Background: The green ship technologies are gaining in importance in diverse areas of ship design. Objective: To explore the energy-saving and environmentally friendly ship during the primary ship designs stage. Methods: A hull form optimization method based on the full parametric modeling is proposed, in which the Computational Fluid Dynamic (CFD) analysis is integrated, and the algorithms of Sobol and NSGA-II are used. Taking a 674 m3 single trawler as an example, the full parametric modeling of forebody hull form is adopted by employing an F-spline curve with the software CAESES and the total resistance of the full-scale ship is computed by the integrated software SHIPFLOW numerically. Results: It is proved that the presented optimization method can engage well in the automation process of the hull form design under the constraints of displacement and longitudinal center of buoyancy. Compared with the initial hull form, the total resistance of the optimal ship at the design speed of 11.5 kn decreases 12.2%. Conclusions: It indicates that the proposed method of hull form optimization based on full parametric modeling proposed in this paper has better engineering applicability and broad application prospect in practical ship design practices.","PeriodicalId":45800,"journal":{"name":"International Shipbuilding Progress","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48627150","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}
R. W. Bos, M. van der Eijk, J.H. den Besten, P. Wellens
Loads due to wave impacts are a limiting factor in the design of liquefied natural gas (LNG) tankers and their insulation. The current methodology considers the load independent from the response of the tank. Better tanks can be designed by knowing the effect of the interaction between the wave loads and the response, however predicting these effects is computationally expensive. In this paper a new application of the non-hydrostatic shallow water equations are presented, namely as a reduced order model (ROM) for fluid structure interaction for wave impacts. Our ROM is compared to a high fidelity model. The proposed ROM is fast and accurately predicts the total impulse and added mass, and therefore the general behaviour of the structure during the free vibration phase. It does however not always accurately predict the maximum force. It is therefore considered an appropriate tool for a first screening of the loads for which fluid-structure interaction is important, after which a more accurate method can be used to evaluate the most interesting cases. A sensitivity study is performed for various impact angles and velocities, showing that the importance of fluid structure interaction depends highly on the specific situation.
{"title":"A reduced order model for FSI of tank walls subject to wave impacts during sloshing","authors":"R. W. Bos, M. van der Eijk, J.H. den Besten, P. Wellens","doi":"10.3233/isp-220003","DOIUrl":"https://doi.org/10.3233/isp-220003","url":null,"abstract":"Loads due to wave impacts are a limiting factor in the design of liquefied natural gas (LNG) tankers and their insulation. The current methodology considers the load independent from the response of the tank. Better tanks can be designed by knowing the effect of the interaction between the wave loads and the response, however predicting these effects is computationally expensive. In this paper a new application of the non-hydrostatic shallow water equations are presented, namely as a reduced order model (ROM) for fluid structure interaction for wave impacts. Our ROM is compared to a high fidelity model. The proposed ROM is fast and accurately predicts the total impulse and added mass, and therefore the general behaviour of the structure during the free vibration phase. It does however not always accurately predict the maximum force. It is therefore considered an appropriate tool for a first screening of the loads for which fluid-structure interaction is important, after which a more accurate method can be used to evaluate the most interesting cases. A sensitivity study is performed for various impact angles and velocities, showing that the importance of fluid structure interaction depends highly on the specific situation.","PeriodicalId":45800,"journal":{"name":"International Shipbuilding Progress","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2022-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48296686","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：