Aiming at the nonlinear sloshing in the LNG tank, a three-dimensional elastic model is established to investigate the fluid structure interaction effect. For the transient flow and the tank motion, the direct coupling method is employed to calculate the interaction between the sloshing and the bulkhead. The finite element software ADINA is adopted to do the computation. The sloshing natural frequency is verified with the results of the theoretical formula. Different wall thicknesses, filling ratios and external excitations are considered and the structure natural frequency, surface elevation and sloshing pressure are obtained. The results of the elastic case are further compared with the rigid results and the nonlinear characteristics are extracted to see the hydro-elastic effect. The sloshing natural frequencies are agreed well with the theoretical results. Due to the influence of the fluid structure interaction, the couple frequencies are obviously less than those of the empty tank. With the increase of the wall thickness, the frequencies of the empty tank and the couple frequencies all increase gradually. For the surface elevation, the thinner the bulkhead thickness is, the more the high frequency component is. The free surface is relatively flat and stable in the rigid tank but tend to be chaotic for the elastic one. Due to the fluid structure interaction, the sloshing pressure of the elastic case presents obvious high-frequency fluctuation and the sloshing pressure in the elastic tank is smaller than that in the rigid tank. This model clearly shows the valuable ability to solve the three dimensional sloshing in the elastic tank.
{"title":"Nonlinear Behaviors of Three Dimensional Sloshing in the LNG Elastic Tank","authors":"Zhongchang Wang, Mei-rong Jiang, Yang Yu","doi":"10.1115/omae2021-61679","DOIUrl":"https://doi.org/10.1115/omae2021-61679","url":null,"abstract":"\u0000 Aiming at the nonlinear sloshing in the LNG tank, a three-dimensional elastic model is established to investigate the fluid structure interaction effect. For the transient flow and the tank motion, the direct coupling method is employed to calculate the interaction between the sloshing and the bulkhead. The finite element software ADINA is adopted to do the computation. The sloshing natural frequency is verified with the results of the theoretical formula. Different wall thicknesses, filling ratios and external excitations are considered and the structure natural frequency, surface elevation and sloshing pressure are obtained. The results of the elastic case are further compared with the rigid results and the nonlinear characteristics are extracted to see the hydro-elastic effect. The sloshing natural frequencies are agreed well with the theoretical results. Due to the influence of the fluid structure interaction, the couple frequencies are obviously less than those of the empty tank. With the increase of the wall thickness, the frequencies of the empty tank and the couple frequencies all increase gradually. For the surface elevation, the thinner the bulkhead thickness is, the more the high frequency component is. The free surface is relatively flat and stable in the rigid tank but tend to be chaotic for the elastic one. Due to the fluid structure interaction, the sloshing pressure of the elastic case presents obvious high-frequency fluctuation and the sloshing pressure in the elastic tank is smaller than that in the rigid tank. This model clearly shows the valuable ability to solve the three dimensional sloshing in the elastic tank.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78565134","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 side-by-side moored offloading configuration has relatively stronger hydrodynamic and mechanical interactions compared to a tandem moored offloading configuration. For instance, due to the narrow gap between FLNG and LNG Carrier, the trapped water resonance induces higher relative motions between the FLNG and LNG Carrier. In addition, due to the partial filling conditions during the offloading operations, the sloshing loads excite ship motions which induce higher loading on the offloading arms. In this research, a time domain sloshing-ship motion coupling analysis module has been developed for analyzing interactions of the side-by-side moored multiple floating platforms. This paper presents the numerical modeling, the validation analysis results, and the sloshing-ship motion coupled effects on the side-by-side offloading analysis.
{"title":"Sloshing Effects on FLNG and LNGC Side-by-Side Offloading","authors":"Bonjun Koo, E. Auburtin, Hyoungchul Kim","doi":"10.1115/omae2021-63778","DOIUrl":"https://doi.org/10.1115/omae2021-63778","url":null,"abstract":"\u0000 A side-by-side moored offloading configuration has relatively stronger hydrodynamic and mechanical interactions compared to a tandem moored offloading configuration. For instance, due to the narrow gap between FLNG and LNG Carrier, the trapped water resonance induces higher relative motions between the FLNG and LNG Carrier. In addition, due to the partial filling conditions during the offloading operations, the sloshing loads excite ship motions which induce higher loading on the offloading arms. In this research, a time domain sloshing-ship motion coupling analysis module has been developed for analyzing interactions of the side-by-side moored multiple floating platforms. This paper presents the numerical modeling, the validation analysis results, and the sloshing-ship motion coupled effects on the side-by-side offloading analysis.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81584444","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}
W. Pauw, R. Hageman, Joris van den Berg, P. Aalberts, Hironori Yamaji, A. Ong
Integrity of mooring system is of high importance in the offshore industry. In-service assessment of loads in the mooring lines is however very challenging. Direct monitoring of mooring line loads through load cells or inclinometers requires subsea installation work and continuous data transmission. Other solutions based on GPS and motion monitoring have been presented as solutions to overcome these limitations [1]. Monitoring solutions based on GPS and motion data provide good practical benefits, because monitoring can be conducted from accessible area. The procedure relies on accurate numerical models to model the relation between global motions and response of the mooring system. In this paper, validation of this monitoring approach for a single unit will be presented. The unit under consideration is a turret-moored unit operating in Australia. In-service measurements of motions, GPS and line tensions are available. A numerical time-domain model of the mooring system was created. This model was used to simulate mooring line tensions due to measured FPSO motions. Using the measured unit response avoids the uncertainty resulting from a prediction of the hydrodynamic response. Measurements from load cells in various mooring lines are available. These measurements were compared against the results obtained from the simulations for validation of the approach. Three different periods, comprising a total of five weeks of data, were examined in more detail. Two periods are mild weather conditions with different dominant wave directions. The third period features heavy weather conditions. In this paper, the data set and numerical model are presented. A comparison between the measured and numerically calculated mooring line forces will be presented. Differences between the calculated and measured forces are examined. This validation study has shown that in-service monitoring of mooring line loads through GPS and motion data provides a new opportunity for mooring integrity assessment with reduced monitoring system complexity.
{"title":"Validation of Mooring Simulations (for Mooring Integrity Assessment) With In-Service Tension Measurements","authors":"W. Pauw, R. Hageman, Joris van den Berg, P. Aalberts, Hironori Yamaji, A. Ong","doi":"10.1115/omae2021-62772","DOIUrl":"https://doi.org/10.1115/omae2021-62772","url":null,"abstract":"\u0000 Integrity of mooring system is of high importance in the offshore industry. In-service assessment of loads in the mooring lines is however very challenging. Direct monitoring of mooring line loads through load cells or inclinometers requires subsea installation work and continuous data transmission. Other solutions based on GPS and motion monitoring have been presented as solutions to overcome these limitations [1].\u0000 Monitoring solutions based on GPS and motion data provide good practical benefits, because monitoring can be conducted from accessible area. The procedure relies on accurate numerical models to model the relation between global motions and response of the mooring system. In this paper, validation of this monitoring approach for a single unit will be presented.\u0000 The unit under consideration is a turret-moored unit operating in Australia. In-service measurements of motions, GPS and line tensions are available. A numerical time-domain model of the mooring system was created. This model was used to simulate mooring line tensions due to measured FPSO motions. Using the measured unit response avoids the uncertainty resulting from a prediction of the hydrodynamic response.\u0000 Measurements from load cells in various mooring lines are available. These measurements were compared against the results obtained from the simulations for validation of the approach. Three different periods, comprising a total of five weeks of data, were examined in more detail. Two periods are mild weather conditions with different dominant wave directions. The third period features heavy weather conditions.\u0000 In this paper, the data set and numerical model are presented. A comparison between the measured and numerically calculated mooring line forces will be presented. Differences between the calculated and measured forces are examined.\u0000 This validation study has shown that in-service monitoring of mooring line loads through GPS and motion data provides a new opportunity for mooring integrity assessment with reduced monitoring system complexity.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"340 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78609850","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 time-domain S-N fatigue analysis and an approach to reliable and robust engineering criticality assessments to supplement or provide an alternative to S-N fatigue assessments of offshore platform structures based on time domain structural response analysis. It also provides recommendations for industry standards to improve guidance for structural integrity assessments of offshore platforms using fracture mechanics. Demand continues to grow in the offshore industry to attain value from captured operational data for a number of purposes, including the reduction of uncertainties in structural integrity assessments during design and over the operational lifetime of floating offshore platforms. Recent advances in time domain structural analysis technology demonstrate substantially more accurate assessments of non-linear platform loadings and responses with enhanced computational efficiency. The current S-N approach for fatigue design and integrity assessments calculates a fatigue damage factor that does not address how loading occurs over time (ABS, DNVGL-RP-C203). For the present study, engineering criticality assessments (ECAs) based on fracture mechanics theory (BS 7910) are applied utilizing time-domain loading information theory. The ECA returns the smallest initial flaws that can grow to a critical size during a design lifetime, which can serve as an indicator of acceptability during design, a technical basis for in-service inspection intervals and facilitates asset integrity and life extension assessments. Critical initial flaws are calculated using the Paris Law (BS 7910) and cumulative fatigue crack growth in two ways: with and without an integrated and consistent check for fracture instability. The results are compared with those from S-N fatigue analyses and recommendations are provided.
{"title":"Engineering Criticality Assessments of Floating Offshore Platforms Based on Time Domain Structural Response Analysis","authors":"J. O’Donnell, J. Kyoung, Sagar Samaria, A. Sablok","doi":"10.1115/omae2021-63796","DOIUrl":"https://doi.org/10.1115/omae2021-63796","url":null,"abstract":"\u0000 This paper presents a time-domain S-N fatigue analysis and an approach to reliable and robust engineering criticality assessments to supplement or provide an alternative to S-N fatigue assessments of offshore platform structures based on time domain structural response analysis. It also provides recommendations for industry standards to improve guidance for structural integrity assessments of offshore platforms using fracture mechanics.\u0000 Demand continues to grow in the offshore industry to attain value from captured operational data for a number of purposes, including the reduction of uncertainties in structural integrity assessments during design and over the operational lifetime of floating offshore platforms. Recent advances in time domain structural analysis technology demonstrate substantially more accurate assessments of non-linear platform loadings and responses with enhanced computational efficiency. The current S-N approach for fatigue design and integrity assessments calculates a fatigue damage factor that does not address how loading occurs over time (ABS, DNVGL-RP-C203).\u0000 For the present study, engineering criticality assessments (ECAs) based on fracture mechanics theory (BS 7910) are applied utilizing time-domain loading information theory. The ECA returns the smallest initial flaws that can grow to a critical size during a design lifetime, which can serve as an indicator of acceptability during design, a technical basis for in-service inspection intervals and facilitates asset integrity and life extension assessments. Critical initial flaws are calculated using the Paris Law (BS 7910) and cumulative fatigue crack growth in two ways: with and without an integrated and consistent check for fracture instability. The results are compared with those from S-N fatigue analyses and recommendations are provided.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"231 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89238462","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}
Negative air gap and wave slamming load on the deck box of drilling semi-submersible units in severe storm have received a great deal of attention, due to the COSL Innovator accident in 2015. Equally important is vertical slamming load on the MODU underdeck, which is less reported in the literature. The present paper attempts to derive characteristic vertical slamming pressure on the deck bottom, based on an extensive model test program for a drilling semi-submersible unit, CM-SD1000. A total of 96 3-hour wave impact tests were conducted including 4 sea states selected along the DNV steepness criterion curve in 3 wave headings. Two critical sea states were identified and each was tested with 16 random realizations in both the head and the beam waves. 8 force panels were installed on the under-deck to capture vertical wave impact events. It is found that the peak slamming pressures obtained can be fitted well with both Weibull and Gumbel probability function. The extreme vertical impact pressure predicted are of the same order of magnitude as the extreme horizontal impact pressure. The present study also shows that rise velocities of the wave surface relative to the deck bottom have a remarkable correlation with the wave slamming pressure in terms of probability distribution. The relative rise velocities can be properly derived from wave probe measurements. This offers an alternative approach to estimate the vertical impact pressure without resort to force panels. In contrast to horizontal wave slamming, the magnitude and frequency of vertical ones simply increases with significant wave height and wave steepness has much less effect. It is found that the extreme vertical impact pressure can be approximated well by a linear function of the significant wave height. The linear relationship, if validated by more tests, may help evaluate structural strength of the deck bottom before wave basin model testing.
{"title":"Underdeck Wave Slamming Model Tests for a Drilling Semi-Submersible Unit","authors":"Li-xin Xu, X. Teng, Jinguang Wang, Sing-Kwan Lee, Jiancheng Liu, Yi-zhi Guo, Longfei Xiao","doi":"10.1115/omae2021-61270","DOIUrl":"https://doi.org/10.1115/omae2021-61270","url":null,"abstract":"\u0000 Negative air gap and wave slamming load on the deck box of drilling semi-submersible units in severe storm have received a great deal of attention, due to the COSL Innovator accident in 2015. Equally important is vertical slamming load on the MODU underdeck, which is less reported in the literature. The present paper attempts to derive characteristic vertical slamming pressure on the deck bottom, based on an extensive model test program for a drilling semi-submersible unit, CM-SD1000.\u0000 A total of 96 3-hour wave impact tests were conducted including 4 sea states selected along the DNV steepness criterion curve in 3 wave headings. Two critical sea states were identified and each was tested with 16 random realizations in both the head and the beam waves. 8 force panels were installed on the under-deck to capture vertical wave impact events. It is found that the peak slamming pressures obtained can be fitted well with both Weibull and Gumbel probability function. The extreme vertical impact pressure predicted are of the same order of magnitude as the extreme horizontal impact pressure.\u0000 The present study also shows that rise velocities of the wave surface relative to the deck bottom have a remarkable correlation with the wave slamming pressure in terms of probability distribution. The relative rise velocities can be properly derived from wave probe measurements. This offers an alternative approach to estimate the vertical impact pressure without resort to force panels.\u0000 In contrast to horizontal wave slamming, the magnitude and frequency of vertical ones simply increases with significant wave height and wave steepness has much less effect. It is found that the extreme vertical impact pressure can be approximated well by a linear function of the significant wave height. The linear relationship, if validated by more tests, may help evaluate structural strength of the deck bottom before wave basin model testing.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","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":"91157117","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}
Jang-Whan Kim, Hyunchul Jang, S. Yeon, Hyunjoe Kim
Wind load is one of the major design load considerations for the hull and mooring of offshore floating facilities. The first step to minimize the uncertainties in wind load is generating an accurate wind profile that satisfies design requirements. Recently, there was a joint-industry effort to develop CFD modeling practices on wind-load estimation in SNAME OC-8 CFD Task Force (OMAE2018-78699). The Task Force developed the modeling practice for the NPD (Norwegian Petroleum Directorate) model commonly used for offshore platform design, and several independent participants in the Task Force successfully validated the practice for a topsides of a semi-submersible platform. The sustainable wind profile was able to be generated within 1% tolerance of the target wind profile, and the calculated wind loads on the topsides from CFD simulations were close to the model test data with low uncertainty levels. In the present study, the numerical modeling for the sustainable ABL is extended to other popular wind models such as the ESDU (Engineering Science Data Unit) and the power-law models. The study is a part of a joint-development project between TechnipFMC, Chevron, and Samsung Heavy Industries. The analytic or numerical formulae of wind speed and turbulent quantities for several RANS (Reynolds-Averaged Navier-Stokes) models are derived for the wind models, and the sustainability of wind profiles are verified.
风荷载是海上浮式设施船体和系泊设计荷载的主要考虑因素之一。最小化风荷载不确定性的第一步是生成满足设计要求的准确风廓线。最近，在SNAME OC-8 CFD Task Force (OMAE2018-78699)中，有一个联合行业努力开发风荷载估计的CFD建模实践。工作组开发了NPD(挪威石油理事会)模型的建模实践，该模型通常用于海上平台设计，工作组的几个独立参与者成功地验证了半潜式平台顶部的实践。可持续风廓线能够在目标风廓线1%的容差范围内生成，CFD模拟计算的上层风荷载与模型试验数据接近，不确定性较低。在本研究中，将可持续ABL的数值模拟扩展到其他流行的风模型，如ESDU(工程科学数据单元)和幂律模型。该研究是TechnipFMC、雪佛龙和三星重工业共同开发项目的一部分。推导了几种RANS (reynolds - average Navier-Stokes)模型的风速和湍流量的解析或数值公式，并验证了风廓线的可持续性。
{"title":"Numerical Modeling of Sustainable Atmospheric Boundary Layer for Offshore Floaters","authors":"Jang-Whan Kim, Hyunchul Jang, S. Yeon, Hyunjoe Kim","doi":"10.1115/omae2021-63807","DOIUrl":"https://doi.org/10.1115/omae2021-63807","url":null,"abstract":"\u0000 Wind load is one of the major design load considerations for the hull and mooring of offshore floating facilities. The first step to minimize the uncertainties in wind load is generating an accurate wind profile that satisfies design requirements.\u0000 Recently, there was a joint-industry effort to develop CFD modeling practices on wind-load estimation in SNAME OC-8 CFD Task Force (OMAE2018-78699). The Task Force developed the modeling practice for the NPD (Norwegian Petroleum Directorate) model commonly used for offshore platform design, and several independent participants in the Task Force successfully validated the practice for a topsides of a semi-submersible platform. The sustainable wind profile was able to be generated within 1% tolerance of the target wind profile, and the calculated wind loads on the topsides from CFD simulations were close to the model test data with low uncertainty levels.\u0000 In the present study, the numerical modeling for the sustainable ABL is extended to other popular wind models such as the ESDU (Engineering Science Data Unit) and the power-law models. The study is a part of a joint-development project between TechnipFMC, Chevron, and Samsung Heavy Industries. The analytic or numerical formulae of wind speed and turbulent quantities for several RANS (Reynolds-Averaged Navier-Stokes) models are derived for the wind models, and the sustainability of wind profiles are verified.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73742918","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}
Xiangbo Liu, C. T. Liong, Nitesh Kumar, Kie Hian Chua, A. Magee, Y. Choo
This paper presents verification of a deep water FPSO with a semi-taut mooring system using model tests and numerical modelling commonly referred to as the hybrid method. The vessel under investigation is a FPSO of 310m in length and 47m in beam with an internal turret mooring system of 12 lines in 2000m water depth. Two configurations of the mooring systems i.e. inline and bisecting are investigated for sea-states up to 1000yr return period. A full depth mooring system has been developed for the FPSO and model tests will be carried out to verify the model. Due to limitations to the size of the model basins, the model tests will be carried out for a truncated mooring setup. Non-linear horizontal stiffness of a single mooring line and the complete mooring system with truncation is compared to that of the existing full depth mooring system. Discrepancies in the vertical forces due to truncation of line length will be discussed in the paper. A numerical model of the truncated set-up will be calibrated using model test results.
{"title":"Hybrid Verification of a Deepwater FPSO Using Truncated Model Tests and Numerical Simulations","authors":"Xiangbo Liu, C. T. Liong, Nitesh Kumar, Kie Hian Chua, A. Magee, Y. Choo","doi":"10.1115/omae2021-62670","DOIUrl":"https://doi.org/10.1115/omae2021-62670","url":null,"abstract":"\u0000 This paper presents verification of a deep water FPSO with a semi-taut mooring system using model tests and numerical modelling commonly referred to as the hybrid method. The vessel under investigation is a FPSO of 310m in length and 47m in beam with an internal turret mooring system of 12 lines in 2000m water depth. Two configurations of the mooring systems i.e. inline and bisecting are investigated for sea-states up to 1000yr return period. A full depth mooring system has been developed for the FPSO and model tests will be carried out to verify the model. Due to limitations to the size of the model basins, the model tests will be carried out for a truncated mooring setup. Non-linear horizontal stiffness of a single mooring line and the complete mooring system with truncation is compared to that of the existing full depth mooring system. Discrepancies in the vertical forces due to truncation of line length will be discussed in the paper. A numerical model of the truncated set-up will be calibrated using model test results.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90631060","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}
B. Bouscasse, A. Califano, Young-Myung Choi, Xu Haihua, Jang-Whan Kim, Young Jun Kim, Sang Hun Lee, H. Lim, Dong-Min Park, M. Peric, Zhi-rong Shen, S. Yeon
There is increasing interest in numerical wave simulations as a tool to design offshore structures, especially for the prediction of stochastic nonlinear wave loads like those related to air-gap and wave impact. Though the simulations cannot replace all experiments, they are now competitive on some topics such as the computations of wind and current coefficients. To proceed further it is necessary to improve the procedure to account for another complex environmental factor, wave motion. This paper addresses an industrial collaboration to develop modeling practices and qualification criteria of CFD-based numerical wave tank for offshore applications. As a part of the effort to develop reliable numerical wave modeling practices in the framework of the “Reproducible Offshore CFD JIP”, qualification criteria are formulated for the wave solutions generated from either potential-flow based codes in Part 1 of this work. Part 2 presents first a set of solutions for forcing the qualified waves obtained with the potential codes in the CFD domain. Those solutions follow a set of coupling protocols previously proposed in the JIP framework. Two potential codes and two CFD solvers are combined, so that four possible methods of generating waves and modalities are described. Two different potential models are considered, one using the higher order spectral method for numerical wave tank (HOS-NWT), and another using the finite-element method in the horizontal direction and a modal expansion after a sigma transform in the vertical direction (solver is called TPNWT). Both are equipped with a breaking model to generate extreme sea states. The two CFD solvers tested are Simcenter STAR-CCM+ and OpenFOAM. Simulation setups are proposed for both software. Simulation results from eight academic or industrial partners are presented for two sets of 2D test cases in deep water, one with regular waves and one with irregular waves, both with one very steep condition (ratio of wave height over wavelength of 10% for regular waves and 1000 year return period for Gulf of Mexico for irregular waves). The irregular waves are simulated for 10 sets of 3 hours to apply a stochastic approach to verify the quality of the waves generated in the numerical domain. Attention is given to the wave spectrum and the ensemble probability of the crest distribution, both obtained from the wave elevation at the center of the domain.
{"title":"Qualification Criteria and the Verification of Numerical Waves: Part 2: CFD-Based Numerical Wave Tank","authors":"B. Bouscasse, A. Califano, Young-Myung Choi, Xu Haihua, Jang-Whan Kim, Young Jun Kim, Sang Hun Lee, H. Lim, Dong-Min Park, M. Peric, Zhi-rong Shen, S. Yeon","doi":"10.1115/omae2021-63710","DOIUrl":"https://doi.org/10.1115/omae2021-63710","url":null,"abstract":"\u0000 There is increasing interest in numerical wave simulations as a tool to design offshore structures, especially for the prediction of stochastic nonlinear wave loads like those related to air-gap and wave impact. Though the simulations cannot replace all experiments, they are now competitive on some topics such as the computations of wind and current coefficients. To proceed further it is necessary to improve the procedure to account for another complex environmental factor, wave motion.\u0000 This paper addresses an industrial collaboration to develop modeling practices and qualification criteria of CFD-based numerical wave tank for offshore applications. As a part of the effort to develop reliable numerical wave modeling practices in the framework of the “Reproducible Offshore CFD JIP”, qualification criteria are formulated for the wave solutions generated from either potential-flow based codes in Part 1 of this work. Part 2 presents first a set of solutions for forcing the qualified waves obtained with the potential codes in the CFD domain. Those solutions follow a set of coupling protocols previously proposed in the JIP framework.\u0000 Two potential codes and two CFD solvers are combined, so that four possible methods of generating waves and modalities are described. Two different potential models are considered, one using the higher order spectral method for numerical wave tank (HOS-NWT), and another using the finite-element method in the horizontal direction and a modal expansion after a sigma transform in the vertical direction (solver is called TPNWT). Both are equipped with a breaking model to generate extreme sea states. The two CFD solvers tested are Simcenter STAR-CCM+ and OpenFOAM. Simulation setups are proposed for both software.\u0000 Simulation results from eight academic or industrial partners are presented for two sets of 2D test cases in deep water, one with regular waves and one with irregular waves, both with one very steep condition (ratio of wave height over wavelength of 10% for regular waves and 1000 year return period for Gulf of Mexico for irregular waves).\u0000 The irregular waves are simulated for 10 sets of 3 hours to apply a stochastic approach to verify the quality of the waves generated in the numerical domain. Attention is given to the wave spectrum and the ensemble probability of the crest distribution, both obtained from the wave elevation at the center of the domain.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"66 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80621578","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}
Giuseppe Blasioli, F. Marchesani, Maurizio Badalini, Vincenzo Luci, Tove Bekkeheien, Arne Ingvar Helland
The transport of CO2 through offshore pipelines is one of the last business that the Operators are beginning to face, in line with the coming needs for climate change mitigations. The scenario for CO2 Capture, Transport and Storage anticipates capture and treatment at local plants, the transportation by ships in a liquid phase at low temperatures (close to −30 °C) to a terminal for the following offshore submarine transportation in a pipeline up to an injection well, for the final (and permanent) storage underground. In order to optimize the operating costs for CO2 transport via pipeline, and to reduce energy consumptions, no heating is applied from ship to pipeline inlet. In such case, the pipeline will reach approximately a temperature of −30 °C in the initial landfall section. The design of the offshore pipeline subject to this operating conditions, very cold fluid inside and a sea water temperature slightly over 0°C outside (North Sea), must face the possibility of ice formation around the pipe. For the Northern Lights project, this possibility has been analyzed and the HDD (Horizontal Directional Drilling) at landfall resulted the only section where the ice formation could jeopardize the pipeline integrity. Detailed assessment for both normal operating conditions and contingency cases has been performed. In the former case, a steady state thermal analysis with analytical method (thermal resistances) has been applied to calculate both the longitudinal, along the pipeline axis, and radial temperature profile: all the water inside the HDD freezes. Therefore, a water circulation system has been studied to prevent the ice formation. The pumping system required to ensure enough water flow has been dimensioned considering pressure losses inside the HDD. Power consumption in the order of 3 kW is expected. The breakdown of the pumps has been analyzed in order to determine the available time before the sea water freeze inside the HDD obstructing any circulation. A transient analysis has been carried out simulating the temperature after water circulation arrest. Both analytical and Finite Element Model have been used to calculate the transient process causing water freezing.
{"title":"Northern Light Offshore Pipeline – Negative Transport Temperature Inside the HDD","authors":"Giuseppe Blasioli, F. Marchesani, Maurizio Badalini, Vincenzo Luci, Tove Bekkeheien, Arne Ingvar Helland","doi":"10.1115/omae2021-63713","DOIUrl":"https://doi.org/10.1115/omae2021-63713","url":null,"abstract":"\u0000 The transport of CO2 through offshore pipelines is one of the last business that the Operators are beginning to face, in line with the coming needs for climate change mitigations.\u0000 The scenario for CO2 Capture, Transport and Storage anticipates capture and treatment at local plants, the transportation by ships in a liquid phase at low temperatures (close to −30 °C) to a terminal for the following offshore submarine transportation in a pipeline up to an injection well, for the final (and permanent) storage underground.\u0000 In order to optimize the operating costs for CO2 transport via pipeline, and to reduce energy consumptions, no heating is applied from ship to pipeline inlet. In such case, the pipeline will reach approximately a temperature of −30 °C in the initial landfall section.\u0000 The design of the offshore pipeline subject to this operating conditions, very cold fluid inside and a sea water temperature slightly over 0°C outside (North Sea), must face the possibility of ice formation around the pipe.\u0000 For the Northern Lights project, this possibility has been analyzed and the HDD (Horizontal Directional Drilling) at landfall resulted the only section where the ice formation could jeopardize the pipeline integrity. Detailed assessment for both normal operating conditions and contingency cases has been performed.\u0000 In the former case, a steady state thermal analysis with analytical method (thermal resistances) has been applied to calculate both the longitudinal, along the pipeline axis, and radial temperature profile: all the water inside the HDD freezes. Therefore, a water circulation system has been studied to prevent the ice formation. The pumping system required to ensure enough water flow has been dimensioned considering pressure losses inside the HDD. Power consumption in the order of 3 kW is expected.\u0000 The breakdown of the pumps has been analyzed in order to determine the available time before the sea water freeze inside the HDD obstructing any circulation. A transient analysis has been carried out simulating the temperature after water circulation arrest. Both analytical and Finite Element Model have been used to calculate the transient process causing water freezing.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"306 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79840552","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}
Nowadays, zero speed fin stabilizer has been initially applied in ship. Whether zero speed fin stabilizer can generate enough lift moment to resist rolling moment or not, determines the anti-rolling effect of ship at zero speed. In the present paper, numerical model is proposed to calculate the lift force and moment of zero speed fin stabilizer. The results of numerical calculation are verified by model test results and the hydrodynamic performance of zero speed fin stabilizer are studied. The numerical results are in good agreement with the model test results. For different swing angular velocity of a zero speed fin stabilizer, the lift force and moment of zero speed fin stabilizer reach the maximum at the same swing angle. For the same swing angle of a zero speed fin stabilizer, the lift force and moment of zero speed fin stabilizer are proportional to the square of angular velocity.
{"title":"Research on the Hydrodynamic Performance of Zero Speed Fin Stabilizer","authors":"Yuefeng Wei, Yi Yang","doi":"10.1115/omae2021-62889","DOIUrl":"https://doi.org/10.1115/omae2021-62889","url":null,"abstract":"\u0000 Nowadays, zero speed fin stabilizer has been initially applied in ship. Whether zero speed fin stabilizer can generate enough lift moment to resist rolling moment or not, determines the anti-rolling effect of ship at zero speed. In the present paper, numerical model is proposed to calculate the lift force and moment of zero speed fin stabilizer. The results of numerical calculation are verified by model test results and the hydrodynamic performance of zero speed fin stabilizer are studied. The numerical results are in good agreement with the model test results. For different swing angular velocity of a zero speed fin stabilizer, the lift force and moment of zero speed fin stabilizer reach the maximum at the same swing angle. For the same swing angle of a zero speed fin stabilizer, the lift force and moment of zero speed fin stabilizer are proportional to the square of angular velocity.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88267091","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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