This paper studies the wave diffraction of a two-dimensional moonpool in a two-layer fluid in finite water depth by using a domain decomposition scheme and an eigenfunction matching method. The formulae of the wave exciting forces, the free surface and internal wave elevations at zero-frequency are derived. Numerical convergence has been assessed by repeating the computations for increasing values of the truncation orders. The present model has been validated by comparing a limiting case with a single-layer fluid case and the comparisons are in general satisfactory. Although the wave exciting forces and free surface wave elevations around resonance frequency are overestimated, the piston mode resonance frequency is well predicted. Two typical configurations with different moonpool widths are selected for computations in both free surface and internal wave modes. It is found that, the wave exciting forces, free surface and internal wave elevations in internal wave mode are much smaller than those in free surface wave mode. In addition, the wave exciting forces in internal wave mode attenuate to zero quickly as incident wave frequency increases. For moonpool with small width, only piston mode resonance can be observed. The piston mode resonance frequencies identified in free surface and internal wave modes are the same. The characteristics of piston mode resonance can also be observed in the horizontal and vertical wave exciting forces. Around the piston mode resonance frequency, the wave exciting forces reach their local maximums. It is revealed that, as moonpool width increases, the piston mode resonance frequency decreases. Meanwhile, it shows that more asymmetric and symmetric sloshing mode resonances appear alternately and occur at higher frequencies than the piston mode resonance. Moreover, the predicted sloshing mode resonance frequencies are compared with those estimated by a simple approximate formula.
{"title":"On Wave Diffraction of a Two-Dimensional Moonpool in a Two-Layer Fluid in Finite Water Depth","authors":"Xingyu Song, Xin Xu, Xinshu Zhang, Y. You","doi":"10.1115/OMAE2018-77528","DOIUrl":"https://doi.org/10.1115/OMAE2018-77528","url":null,"abstract":"This paper studies the wave diffraction of a two-dimensional moonpool in a two-layer fluid in finite water depth by using a domain decomposition scheme and an eigenfunction matching method. The formulae of the wave exciting forces, the free surface and internal wave elevations at zero-frequency are derived. Numerical convergence has been assessed by repeating the computations for increasing values of the truncation orders. The present model has been validated by comparing a limiting case with a single-layer fluid case and the comparisons are in general satisfactory. Although the wave exciting forces and free surface wave elevations around resonance frequency are overestimated, the piston mode resonance frequency is well predicted. Two typical configurations with different moonpool widths are selected for computations in both free surface and internal wave modes. It is found that, the wave exciting forces, free surface and internal wave elevations in internal wave mode are much smaller than those in free surface wave mode. In addition, the wave exciting forces in internal wave mode attenuate to zero quickly as incident wave frequency increases. For moonpool with small width, only piston mode resonance can be observed. The piston mode resonance frequencies identified in free surface and internal wave modes are the same. The characteristics of piston mode resonance can also be observed in the horizontal and vertical wave exciting forces. Around the piston mode resonance frequency, the wave exciting forces reach their local maximums. It is revealed that, as moonpool width increases, the piston mode resonance frequency decreases. Meanwhile, it shows that more asymmetric and symmetric sloshing mode resonances appear alternately and occur at higher frequencies than the piston mode resonance. Moreover, the predicted sloshing mode resonance frequencies are compared with those estimated by a simple approximate formula.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"138 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132435735","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}
Estimating moonpool piston mode response at resonance is important for operation safety. This is a difficult task, in particular, due to nonlinear nature of the moonpool response connected to the damping imposed by the flow separation at the moonpool’s inlet. In the present work, the applicability of a simplified model, based on decomposing the problem into potential and viscous components, is investigated. The moonpool piston mode response is modeled as an additional degree of freedom. The coupling terms between this new degree of freedom and other vessel’s modes of motions are calculated based on potential flow calculations. Radiation and diffraction problems are considered separately. A finite volume solver with linearized boundary conditions is used to obtain the moonpool response under forced vertical motions. A quadratic damping model is fitted to the obtained responses and added to the free-surface condition of the potential flow formulation. The problem is solved both in frequency and time-domain. The validity of the obtained model is investigated by model test comparison for a dummy vessel with moonpool undergoing regular and irregular forced oscillations, as well as an offshore operation vessel with moonpool exposed to irregular waves. The benefits and shortcomings of the model are discussed. It is suggested that this method can be used as a practical tool to address moonpool piston mode response in irregular waves.
{"title":"Investigating a Simplified Model for Moonpool Piston Mode Response in Irregular Waves","authors":"Babak Ommani, T. Kristiansen, K. Berget","doi":"10.1115/OMAE2018-78352","DOIUrl":"https://doi.org/10.1115/OMAE2018-78352","url":null,"abstract":"Estimating moonpool piston mode response at resonance is important for operation safety. This is a difficult task, in particular, due to nonlinear nature of the moonpool response connected to the damping imposed by the flow separation at the moonpool’s inlet. In the present work, the applicability of a simplified model, based on decomposing the problem into potential and viscous components, is investigated. The moonpool piston mode response is modeled as an additional degree of freedom. The coupling terms between this new degree of freedom and other vessel’s modes of motions are calculated based on potential flow calculations. Radiation and diffraction problems are considered separately. A finite volume solver with linearized boundary conditions is used to obtain the moonpool response under forced vertical motions. A quadratic damping model is fitted to the obtained responses and added to the free-surface condition of the potential flow formulation. The problem is solved both in frequency and time-domain. The validity of the obtained model is investigated by model test comparison for a dummy vessel with moonpool undergoing regular and irregular forced oscillations, as well as an offshore operation vessel with moonpool exposed to irregular waves. The benefits and shortcomings of the model are discussed. It is suggested that this method can be used as a practical tool to address moonpool piston mode response in irregular waves.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"241 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121342919","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}
Martin L. van Wijngaarden, P. Meijers, T. Raaijmakers, R. Jager, K. Gavin
In current modelling of excess pore pressures (EPPs) below marine structures, the irregular nature of cyclic loads and the real storm development are not taken into account. The effect of the irregular cyclic loading in time is investigated in this paper. The wind, wave and turbine loads on a gravity based foundation (GBF) are derived in the frequency domain. The real storm development is based on the CoastDat dataset. The load input is used in a program which takes the generation and dissipation of pore pressures under cyclic loading into account. Also, densification is included. The results show that the first storm in the lifetime of the GBF results in the highest EPPs. The EPP decreases in time, due to significant dissipation and densification during the build-up of a storm. Therefore, not the storms with the largest cyclic loads but the storms with the fastest build-up result in the highest EPPs, since this limits the process of densification. A large scatter is found in the maximum values of EPPs due to the irregular nature of the loads.
{"title":"Gravity Based Foundations for Offshore Wind Turbines: Cyclic Loading and Liquefaction","authors":"Martin L. van Wijngaarden, P. Meijers, T. Raaijmakers, R. Jager, K. Gavin","doi":"10.1115/OMAE2018-77082","DOIUrl":"https://doi.org/10.1115/OMAE2018-77082","url":null,"abstract":"In current modelling of excess pore pressures (EPPs) below marine structures, the irregular nature of cyclic loads and the real storm development are not taken into account. The effect of the irregular cyclic loading in time is investigated in this paper. The wind, wave and turbine loads on a gravity based foundation (GBF) are derived in the frequency domain. The real storm development is based on the CoastDat dataset. The load input is used in a program which takes the generation and dissipation of pore pressures under cyclic loading into account. Also, densification is included. The results show that the first storm in the lifetime of the GBF results in the highest EPPs. The EPP decreases in time, due to significant dissipation and densification during the build-up of a storm. Therefore, not the storms with the largest cyclic loads but the storms with the fastest build-up result in the highest EPPs, since this limits the process of densification. A large scatter is found in the maximum values of EPPs due to the irregular nature of the loads.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122518445","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}
Assessment of scour below pipelines and gravity based structures in a submarine system is revisited with evaluation of data from two inspections and results for semi-empirical simplified models. Usually semi-empirical models are based on small scale experimental data that normally consider uniform and noncohesive sediments and have been questioned as to their practical applications. Recent local metocean data is used to revisit predictions of onset of scour and scour depth for the system, which are compared to survey statistics.
{"title":"Evaluation of Existing Semi-Empirical Models of Scour at a Submarine System","authors":"V. S. Rego, C. P. D. Santos","doi":"10.1115/OMAE2018-78157","DOIUrl":"https://doi.org/10.1115/OMAE2018-78157","url":null,"abstract":"Assessment of scour below pipelines and gravity based structures in a submarine system is revisited with evaluation of data from two inspections and results for semi-empirical simplified models. Usually semi-empirical models are based on small scale experimental data that normally consider uniform and noncohesive sediments and have been questioned as to their practical applications. Recent local metocean data is used to revisit predictions of onset of scour and scour depth for the system, which are compared to survey statistics.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124662133","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}
Charaf Ouled Housseine, Š. Malenica, G. D. Hauteclocque, Xiaobo Chen
Wave diffraction-radiation by a porous body is investigated here. Linear potential flow theory is used and the associated Boundary Value Problem (BVP) is formulated in frequency domain within a linear porosity condition. First, a semi-analytical solution for a truncated porous circular cylinder is developed using the dedicated eigenfunction expansion method. Then the general case of wave diffraction-radiation by a porous body with an arbitrary shape is discussed and solved through Boundary Integral Equation Method (BIEM). The main goal of these developments is to adapt the existing diffraction-radiation code (HYDROSTAR) for that type of applications. Thus the present study of the porous cylinder consists a validation work of (BIEM) numerical implementation. Excellent agreement between analytical and numerical results is observed. Porosity influence on wave exciting forces, added mass and damping is also investigated.
{"title":"Hydrodynamic Interactions of the Truncated Porous Vertical Circular Cylinder With Water Waves","authors":"Charaf Ouled Housseine, Š. Malenica, G. D. Hauteclocque, Xiaobo Chen","doi":"10.1115/OMAE2018-78221","DOIUrl":"https://doi.org/10.1115/OMAE2018-78221","url":null,"abstract":"Wave diffraction-radiation by a porous body is investigated here. Linear potential flow theory is used and the associated Boundary Value Problem (BVP) is formulated in frequency domain within a linear porosity condition. First, a semi-analytical solution for a truncated porous circular cylinder is developed using the dedicated eigenfunction expansion method. Then the general case of wave diffraction-radiation by a porous body with an arbitrary shape is discussed and solved through Boundary Integral Equation Method (BIEM).\u0000 The main goal of these developments is to adapt the existing diffraction-radiation code (HYDROSTAR) for that type of applications. Thus the present study of the porous cylinder consists a validation work of (BIEM) numerical implementation. Excellent agreement between analytical and numerical results is observed. Porosity influence on wave exciting forces, added mass and damping is also investigated.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117177995","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}
Jack-up rigs are often employed in close proximity to piled platforms, therefore the penetration process of spudcan may have a certain effect on the deformation and bearing capacity of adjacent piles. Firstly, the feasibility of using explicit dynamics algorithm to calculate the bearing capacity of pile is verified in this paper. The optimal result of this algorithm is compared with the results of static implicit algorithm and API specification. Secondly, Arbitrary Lagrangian-Eularian (ALE) adaptive meshing is used to study the penetration process of spudcan. The effects of soil strength, ALE boundary size, mesh size and soil elastic-modulus on calculation results of penetration depth studied in this paper are to determine the optimal numerical scheme. Based on the above analysis, the effect of spudcan penetration on the bearing capacity of adjacent piles with different clearances and its law are under research by using the optimal numerical scheme. The simulation results showing computation efficiency and accuracy can be improved by using this numerical scheme, in which the amount of pile radial mesh is 8, the amount of pile peripheral mesh is 4 and the load speed is 0.1m/s. The spudcan penetration leads to the increment of bearing capacity and this effect reduces with the increment of edge-to-edge clearance between spudcan and pile.
{"title":"Study on ALE Method for Simulating Spudcan Penetrating Near Piles","authors":"Wang Jiayu, L. Run, Liang Chao, Xiao Hui, Wan Jun","doi":"10.1115/OMAE2018-78493","DOIUrl":"https://doi.org/10.1115/OMAE2018-78493","url":null,"abstract":"Jack-up rigs are often employed in close proximity to piled platforms, therefore the penetration process of spudcan may have a certain effect on the deformation and bearing capacity of adjacent piles. Firstly, the feasibility of using explicit dynamics algorithm to calculate the bearing capacity of pile is verified in this paper. The optimal result of this algorithm is compared with the results of static implicit algorithm and API specification. Secondly, Arbitrary Lagrangian-Eularian (ALE) adaptive meshing is used to study the penetration process of spudcan. The effects of soil strength, ALE boundary size, mesh size and soil elastic-modulus on calculation results of penetration depth studied in this paper are to determine the optimal numerical scheme. Based on the above analysis, the effect of spudcan penetration on the bearing capacity of adjacent piles with different clearances and its law are under research by using the optimal numerical scheme. The simulation results showing computation efficiency and accuracy can be improved by using this numerical scheme, in which the amount of pile radial mesh is 8, the amount of pile peripheral mesh is 4 and the load speed is 0.1m/s. The spudcan penetration leads to the increment of bearing capacity and this effect reduces with the increment of edge-to-edge clearance between spudcan and pile.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126884864","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}
With pile installation being an important part of the total project cost, improving the efficiency of the offshore operations would require resolving the uncertainties in how different installation methods influence pile capacity. This paper describes a programme of testing involving static loading tests on eight 165 mm diameter open-ended steel tubes driven into medium dense siliceous sand at a well-characterized test site in Perth, Western Australia. Six piles were installed by impact driving under two different driving frequencies, and two piles were installed by vibration with the aim of identifying the effects of impact frequency on the response of driven piles to static axial and lateral loading. It was found that the tension capacity of piles measured 1 week after installation was not significantly dependent on the impact frequency and that these piles had approximately the same capacity as the piles installed by vibration. First time load tests performed 4 months after the initial tests indicated that all pile types had a similar set-up characteristic. Inspection of static tests on lateral behavior of vibrated and impact driven piles suggests that installation method has no impact on the lateral capacity.
{"title":"Field Study on the Effects of Impact Frequency on the Axial and Lateral Capacity of Driven Pipe Piles in Sand","authors":"I. Anusic, B. Lehane, G. Eiksund, M. Liingaard","doi":"10.1115/OMAE2018-78428","DOIUrl":"https://doi.org/10.1115/OMAE2018-78428","url":null,"abstract":"With pile installation being an important part of the total project cost, improving the efficiency of the offshore operations would require resolving the uncertainties in how different installation methods influence pile capacity. This paper describes a programme of testing involving static loading tests on eight 165 mm diameter open-ended steel tubes driven into medium dense siliceous sand at a well-characterized test site in Perth, Western Australia. Six piles were installed by impact driving under two different driving frequencies, and two piles were installed by vibration with the aim of identifying the effects of impact frequency on the response of driven piles to static axial and lateral loading. It was found that the tension capacity of piles measured 1 week after installation was not significantly dependent on the impact frequency and that these piles had approximately the same capacity as the piles installed by vibration. First time load tests performed 4 months after the initial tests indicated that all pile types had a similar set-up characteristic. Inspection of static tests on lateral behavior of vibrated and impact driven piles suggests that installation method has no impact on the lateral capacity.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114449375","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. Magee, Aichun Feng, K. Karthikeyan, Xiang Liu, D. Yan
Experimental and numerical studies are carried out to examine the moonpool gap resonance for a drillship at both stationary position and forward speed conditions. The moonpool size and draft are also changed to study their effects for the gap resonance phenomenon. An OpenFOAM based CFD model is developed and the numerical results show good agreement with model tests. Both piston and sloshing modes gap resonances are clearly observed. The study shows that the resonance frequency and RAO of the wave elevation inside the moonpool are subject to the effects of moonpool length, drill ship draft and ship forward speed. The model test shows that moonpool elevation RAO generally significantly increases in head seas and noticeably decreases in following seas condition. It is interesting to notice that the wave flume sidewall significantly depresses the moonpool elevation RAO at a certain frequency regardless of moonpool length and draft. Further study shows that the presence of the flume sidewall results in a trapped mode that coincides with the moonpool piston mode resonance at zero speed. This depresses the peak of the moonpool resonance, which occurs at the same frequency.
{"title":"Experimental and Numerical Study for Gap Resonance of Drillship Moonpool in Waves With/Without Forward Speed","authors":"A. Magee, Aichun Feng, K. Karthikeyan, Xiang Liu, D. Yan","doi":"10.1115/OMAE2018-78561","DOIUrl":"https://doi.org/10.1115/OMAE2018-78561","url":null,"abstract":"Experimental and numerical studies are carried out to examine the moonpool gap resonance for a drillship at both stationary position and forward speed conditions. The moonpool size and draft are also changed to study their effects for the gap resonance phenomenon. An OpenFOAM based CFD model is developed and the numerical results show good agreement with model tests. Both piston and sloshing modes gap resonances are clearly observed. The study shows that the resonance frequency and RAO of the wave elevation inside the moonpool are subject to the effects of moonpool length, drill ship draft and ship forward speed. The model test shows that moonpool elevation RAO generally significantly increases in head seas and noticeably decreases in following seas condition. It is interesting to notice that the wave flume sidewall significantly depresses the moonpool elevation RAO at a certain frequency regardless of moonpool length and draft. Further study shows that the presence of the flume sidewall results in a trapped mode that coincides with the moonpool piston mode resonance at zero speed. This depresses the peak of the moonpool resonance, which occurs at the same frequency.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132015554","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 study, a new type of suction pile foundation for floating structures, namely group suction piles, was proposed to improve the shortcomings of conventional single suction piles. Small-scale model tests were performed to estimate the horizontal behavior of single suction piles and group suction piles with different pile spacing (2, 3 and 4 times the pile diameter). The horizontal behavior of group suction piles with different pile spacing was analyzed for various loading locations based on the model tests. For the given group pile configurations (a group pile having 9 component piles with a pile formation of 3 × 3), the horizontal resistance increased with increasing pile spacing. The maximum ultimate horizontal resistances were found at the loading locations of 50% of the embedded depth. Unlikely in the single suction pile case, the significantly maintained residual resistances were found for group suction piles. The residual resistances of group suction piles were at least higher than 40% of the corresponding ultimate horizontal resistances.
{"title":"An Experimental Comparison of Horizontal Resistance of Single Suction Pile and Group Suction Piles","authors":"Juhyung Lee, Hakman Kim, Jinwoo Cho","doi":"10.1115/OMAE2018-77192","DOIUrl":"https://doi.org/10.1115/OMAE2018-77192","url":null,"abstract":"In this study, a new type of suction pile foundation for floating structures, namely group suction piles, was proposed to improve the shortcomings of conventional single suction piles. Small-scale model tests were performed to estimate the horizontal behavior of single suction piles and group suction piles with different pile spacing (2, 3 and 4 times the pile diameter). The horizontal behavior of group suction piles with different pile spacing was analyzed for various loading locations based on the model tests. For the given group pile configurations (a group pile having 9 component piles with a pile formation of 3 × 3), the horizontal resistance increased with increasing pile spacing. The maximum ultimate horizontal resistances were found at the loading locations of 50% of the embedded depth. Unlikely in the single suction pile case, the significantly maintained residual resistances were found for group suction piles. The residual resistances of group suction piles were at least higher than 40% of the corresponding ultimate horizontal resistances.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131979322","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}
Understanding the physics of sloshing wave impacts is necessary for the improvement of sloshing assessment methodology based on sloshing model tests, for LNG membrane tanks on floating structures. The phase change between natural gas and liquefied natural gas is one of the physical phenomena involved during a LNG wave impact but is not taken into account during sloshing model tests. In this paper, some recent numerical and analytical works on the influence of phase change are summarized and discussed. For the impact of an ideally shaped wave, phase change influences two different steps of the impact in different ways: during the gas escape phase, phase change leads to a higher impact velocity; for entrapped gas pockets, phase change causes a reduction of the pressure in the gas pocket. However, this influence is quantitatively small. The generalization to more realistic wave shapes (including e.g. liquid aeration) should be the focus of future works.
{"title":"Numerical Study of Phase Change Influence on Wave Impact Loads in LNG Tanks on Floating Structures","authors":"M. Ancellin, L. Brosset, J. Ghidaglia","doi":"10.1115/OMAE2018-78643","DOIUrl":"https://doi.org/10.1115/OMAE2018-78643","url":null,"abstract":"Understanding the physics of sloshing wave impacts is necessary for the improvement of sloshing assessment methodology based on sloshing model tests, for LNG membrane tanks on floating structures. The phase change between natural gas and liquefied natural gas is one of the physical phenomena involved during a LNG wave impact but is not taken into account during sloshing model tests.\u0000 In this paper, some recent numerical and analytical works on the influence of phase change are summarized and discussed. For the impact of an ideally shaped wave, phase change influences two different steps of the impact in different ways: during the gas escape phase, phase change leads to a higher impact velocity; for entrapped gas pockets, phase change causes a reduction of the pressure in the gas pocket. However, this influence is quantitatively small.\u0000 The generalization to more realistic wave shapes (including e.g. liquid aeration) should be the focus of future works.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124833791","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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