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}
Filipe Salvador Lopes, Joel Sena Sales Junior, Emerson Martins de Andrade, A. C. Fernandes
Due to risks involved during the installation of subsea equipment, it is necessary to simulate the installation process to determine a safe operating window. However, most of the software capable of running these kinds of simulations are very expensive, and these simulations usually take a long time to be made. It is then very convenient to develop a simplified model, capable of running these analyses in a short period of time while still providing us with reliable results. This model was developed using the Python programming language, where a fourth-order Runge Kutta method was implemented to solve the equation of motions that governs the manifold’s installation process. The assumptions are that the wave forces are applied to the ship executing the manifold installation. The ship’s motions were applied at the top of the cable, connected to the crane, so the manifold motions underwater and the cable tension could be calculated. Previously, a simplified one-degree of freedom (1DoF) model was developed and compared to other numerical models and experimental data. In this present work, the model was then expanded to motions in a vertical plane, that is, three degrees of freedom (3 DoF), in order to better represent the physics of the real problem. Its results were then compared to the ones obtained by the 1 DoF model and to the experimental results. The 3 DoF model resulted in a dynamic response closer to the ones observed in the experiments, which shows that it is a better representation of the problem.
{"title":"Development of a Simplified Three Degrees of Freedom Model to Represent the Installation of a Subsea Manifold","authors":"Filipe Salvador Lopes, Joel Sena Sales Junior, Emerson Martins de Andrade, A. C. Fernandes","doi":"10.1115/omae2021-62813","DOIUrl":"https://doi.org/10.1115/omae2021-62813","url":null,"abstract":"\u0000 Due to risks involved during the installation of subsea equipment, it is necessary to simulate the installation process to determine a safe operating window. However, most of the software capable of running these kinds of simulations are very expensive, and these simulations usually take a long time to be made. It is then very convenient to develop a simplified model, capable of running these analyses in a short period of time while still providing us with reliable results.\u0000 This model was developed using the Python programming language, where a fourth-order Runge Kutta method was implemented to solve the equation of motions that governs the manifold’s installation process. The assumptions are that the wave forces are applied to the ship executing the manifold installation. The ship’s motions were applied at the top of the cable, connected to the crane, so the manifold motions underwater and the cable tension could be calculated.\u0000 Previously, a simplified one-degree of freedom (1DoF) model was developed and compared to other numerical models and experimental data. In this present work, the model was then expanded to motions in a vertical plane, that is, three degrees of freedom (3 DoF), in order to better represent the physics of the real problem. Its results were then compared to the ones obtained by the 1 DoF model and to the experimental results. The 3 DoF model resulted in a dynamic response closer to the ones observed in the experiments, which shows that it is a better representation of the problem.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"332 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83828346","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}
Crime against women in India Most of the cases in 2021 will be kidnapping and kidnapping, rape, domestic violence, dowry deaths and assaults, the report said. Also, 107 girls were subjected to acid attacks, 1,580 girls were kidnapped, 15 girls were sold and 2,668 girls were victims of cyber crimes. One of the most common crimes in India is rape. Penile rape under the Criminal Law (Amendment) Act, 2013 and defines as non-penile penetration. lady's frame openings without her consent. According to the National Crime Archives, a female is raped every 20 mins in India. For the purposes of this sub-phase, "dowry" means Dowry Prohibition Act, 1961 (28 of 1961) same as in section 2. (2) One who causes loss of life by dowry in 2021; nearly 6.8 thousand cases of dowry death were reported in India. This has been a gradual decline since 2014, when the number was around 8.5 thousand. One of the most common crimes in India is rape. Penile rape under the Criminal Law (Amendment) Act, 2013 and defines as non-penile penetration. PROMETHEE (Priority Ranking System Method for Crime against women in India) About PROMETHEE methods and usage to uncover current research to classify and explain A classification scheme and a comprehensive literature review is presented in this Alternative of Dowry Deaths, Abetment to Suicide of Women, Miscarriage, Acid Attack, Attempt to Acid Attack and Evaluation of parameters in Cases Sent for Trial during the year - Col. (4) 2021, Cases Sent for Trial during the year - Col. (4) 2020, Cases Sent for Trial during the year - Col. (4) 2019, Cases Sent for Trial during the year - Col. (4) 2018, Cases Sent for Trial during the year - Col. (4) 2017. Acid Attack is got the first rank whereas is the Abetment to Suicide of Women is having the Lowest rank.
{"title":"A Study for Different Crime against women in India by using PROMETHEE Methods","authors":"","doi":"10.46632/rmc/1/1/23","DOIUrl":"https://doi.org/10.46632/rmc/1/1/23","url":null,"abstract":"Crime against women in India Most of the cases in 2021 will be kidnapping and kidnapping, rape, domestic violence, dowry deaths and assaults, the report said. Also, 107 girls were subjected to acid attacks, 1,580 girls were kidnapped, 15 girls were sold and 2,668 girls were victims of cyber crimes. One of the most common crimes in India is rape. Penile rape under the Criminal Law (Amendment) Act, 2013 and defines as non-penile penetration. lady's frame openings without her consent. According to the National Crime Archives, a female is raped every 20 mins in India. For the purposes of this sub-phase, \"dowry\" means Dowry Prohibition Act, 1961 (28 of 1961) same as in section 2. (2) One who causes loss of life by dowry in 2021; nearly 6.8 thousand cases of dowry death were reported in India. This has been a gradual decline since 2014, when the number was around 8.5 thousand. One of the most common crimes in India is rape. Penile rape under the Criminal Law (Amendment) Act, 2013 and defines as non-penile penetration. PROMETHEE (Priority Ranking System Method for Crime against women in India) About PROMETHEE methods and usage to uncover current research to classify and explain A classification scheme and a comprehensive literature review is presented in this Alternative of Dowry Deaths, Abetment to Suicide of Women, Miscarriage, Acid Attack, Attempt to Acid Attack and Evaluation of parameters in Cases Sent for Trial during the year - Col. (4) 2021, Cases Sent for Trial during the year - Col. (4) 2020, Cases Sent for Trial during the year - Col. (4) 2019, Cases Sent for Trial during the year - Col. (4) 2018, Cases Sent for Trial during the year - Col. (4) 2017. Acid Attack is got the first rank whereas is the Abetment to Suicide of Women is having the Lowest rank.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"420 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75024816","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}
India is undergoing economic change. Cities now have better quality of life, and they are now crucial hubs for human existence. The increase in urbanization of Indian cities was facilitated by this influx of people. Prosperity and changing lifestyles brought about by a booming economy made reliance on private vehicles essential. The total demand for travel has accelerated along with population expansion and increased car ownership, but the supply side has lagged behind demand and there are numerous external variables associated to transportation, such as accidents, congestion, pollution, inequality, etc. Promoting and promoting sustainability is important in the contemporary urban transportation environment, sustainable transportation policies. These policies' principal goal is to change people's travel habits, or, in other words, to alter the travel environment. However, many of these rules' ramifications are unclear or complicated. As a result, it is critical that decision-makers are informed of the effects of such policies before adopting and putting them into practice. Models of travel demand can be used in this situation to forecast future travel demand under various policy scenarios. In order to analyze sustainable transportation strategies, this study analyses the possibilities of travel demand models already in use in India. The study discovered that the trip-based, four-step aggregate method used in India as the standard model system was nsufficient for studying sustainable transportation policy. An analysis of an alternative strategy known as activity-based travel demand modeling revealed that it could manage such policies better than traditional models and was useful in selecting the best combination of policies for particular circumstances. Since India has not yet created an operational activity-based travel demand modeling system, the study concludes by proposing a conceptual framework for an integrated activity-based demand model based on the needs identified within the review's framework. In accordance with people's current activity-travel behavior, it can be utilized to create modified and verified applications for existing travel demand models. The final result is done by using the EDAS method. Delhi is highest Value and Agra is lowest value.
{"title":"A Study on Impact of Sustainable Transportation Systems Indian Cities Using For EDAS Methods","authors":"","doi":"10.46632/rmc/1/1/22","DOIUrl":"https://doi.org/10.46632/rmc/1/1/22","url":null,"abstract":"India is undergoing economic change. Cities now have better quality of life, and they are now crucial hubs for human existence. The increase in urbanization of Indian cities was facilitated by this influx of people. Prosperity and changing lifestyles brought about by a booming economy made reliance on private vehicles essential. The total demand for travel has accelerated along with population expansion and increased car ownership, but the supply side has lagged behind demand and there are numerous external variables associated to transportation, such as accidents, congestion, pollution, inequality, etc. Promoting and promoting sustainability is important in the contemporary urban transportation environment, sustainable transportation policies. These policies' principal goal is to change people's travel habits, or, in other words, to alter the travel environment. However, many of these rules' ramifications are unclear or complicated. As a result, it is critical that decision-makers are informed of the effects of such policies before adopting and putting them into practice. Models of travel demand can be used in this situation to forecast future travel demand under various policy scenarios. In order to analyze sustainable transportation strategies, this study analyses the possibilities of travel demand models already in use in India. The study discovered that the trip-based, four-step aggregate method used in India as the standard model system was nsufficient for studying sustainable transportation policy. An analysis of an alternative strategy known as activity-based travel demand modeling revealed that it could manage such policies better than traditional models and was useful in selecting the best combination of policies for particular circumstances. Since India has not yet created an operational activity-based travel demand modeling system, the study concludes by proposing a conceptual framework for an integrated activity-based demand model based on the needs identified within the review's framework. In accordance with people's current activity-travel behavior, it can be utilized to create modified and verified applications for existing travel demand models. The final result is done by using the EDAS method. Delhi is highest Value and Agra is lowest value.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"96 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75980084","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}
Concepts of process orientation basically technical and organizational compromise to align imperatives and without a solid mechanism for doing so leverage the benefits of ERP to their full potential can’t feel. The system recommends that measuring take place from a balanced viewpoint with the goal of delivering relevant information that may facilitate decision-making, which can assist accomplish the corporate objectives and, as a result, drive the organization competitively forward. In this work, risk in ERP project by COPRAS MCDM approach is presented for estimation as a result of this study, here are some key points to mitigate to avoid failure proves that risks complex architecture and a greater number of modules, complex structure and less top management support of an ERP project.
{"title":"Risk Assessment in Enterprise Resource Planning by COPRAS Shadow","authors":"","doi":"10.46632/rmc/1/1/21","DOIUrl":"https://doi.org/10.46632/rmc/1/1/21","url":null,"abstract":"Concepts of process orientation basically technical and organizational compromise to align imperatives and without a solid mechanism for doing so leverage the benefits of ERP to their full potential can’t feel. The system recommends that measuring take place from a balanced viewpoint with the goal of delivering relevant information that may facilitate decision-making, which can assist accomplish the corporate objectives and, as a result, drive the organization competitively forward. In this work, risk in ERP project by COPRAS MCDM approach is presented for estimation as a result of this study, here are some key points to mitigate to avoid failure proves that risks complex architecture and a greater number of modules, complex structure and less top management support of an ERP project.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84574468","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}
P. Barros, E. Carlberg, I. S. Høgsæt, M. Karimi, J. Braun, E. Gooijer, P. Vargas
Chevron Corporation and Bluewater Energy Services (BES) performed a chain out-of-plane bending (OPB) test, called OPB MAX hereafter, at DNV GL’s laboratory in Høvik-Norway. The test was performed to study the OPB phenomenon for a chain diameter which was larger than the maximum diameter tested by the OPB JIP. The goal was to understand chain OPB physics for such a large diameter, measure interlink stiffness and maximum sliding moments and validate BES’ in-house finite element model. The current study is a collaboration between all involved parties and the results will be presented in three papers. The first paper summarizes the test setup and instrumentation. The second paper describes the test results, compares them with the OPB JIP estimations and tries to describe the chain OPB physics. The third and the last paper presents the FEA results performed by BES’ in-house finite element model. This paper is the first of the three and focuses on the test setup and instrumentation. The testing machine has been developed by DNV GL and is capable of applying tensions up to 350 t and interlink rotations in the range of ±3 degrees. Two 7-link chain specimens of R4 and R4s grades, both with the nominal diameter of 168 mm were tested at five tension levels from 150, to 350 t. Testing was performed in both wet and dry conditions. Twenty strain gauges were used to measure 3 OPB and 2 IPB moments at 5 mid-link positions. Twelve strain gauge rosettes were used on 3 links to evaluate SCF’s on the OPB hotspots. Seven inclinometers were used to monitor link rotations. DNV GL utilized a digital image processing tool to capture relative movements of chain links and developed a specific data processing tool to calculate the interlink stiffness, perform statistical analysis and provide several levels of data evaluation and comparison between the tests. The paper will provide a description of the test matrix and test objectives are given with the background of the previously performed OPB tests. Next a detailed description of the test rig is presented including the utilized instrumentation. Finally, an explanation of the implemented real-time test monitoring and the performed post-processing on the readings, in line with the test objectives is mentioned. The initial test results are briefly provided at the end.
{"title":"Out-of-Plane Bending (OPB) Test of Large Diameter Mooring Chains","authors":"P. Barros, E. Carlberg, I. S. Høgsæt, M. Karimi, J. Braun, E. Gooijer, P. Vargas","doi":"10.1115/omae2020-18805","DOIUrl":"https://doi.org/10.1115/omae2020-18805","url":null,"abstract":"\u0000 Chevron Corporation and Bluewater Energy Services (BES) performed a chain out-of-plane bending (OPB) test, called OPB MAX hereafter, at DNV GL’s laboratory in Høvik-Norway. The test was performed to study the OPB phenomenon for a chain diameter which was larger than the maximum diameter tested by the OPB JIP. The goal was to understand chain OPB physics for such a large diameter, measure interlink stiffness and maximum sliding moments and validate BES’ in-house finite element model. The current study is a collaboration between all involved parties and the results will be presented in three papers. The first paper summarizes the test setup and instrumentation. The second paper describes the test results, compares them with the OPB JIP estimations and tries to describe the chain OPB physics. The third and the last paper presents the FEA results performed by BES’ in-house finite element model. This paper is the first of the three and focuses on the test setup and instrumentation.\u0000 The testing machine has been developed by DNV GL and is capable of applying tensions up to 350 t and interlink rotations in the range of ±3 degrees. Two 7-link chain specimens of R4 and R4s grades, both with the nominal diameter of 168 mm were tested at five tension levels from 150, to 350 t. Testing was performed in both wet and dry conditions. Twenty strain gauges were used to measure 3 OPB and 2 IPB moments at 5 mid-link positions. Twelve strain gauge rosettes were used on 3 links to evaluate SCF’s on the OPB hotspots. Seven inclinometers were used to monitor link rotations. DNV GL utilized a digital image processing tool to capture relative movements of chain links and developed a specific data processing tool to calculate the interlink stiffness, perform statistical analysis and provide several levels of data evaluation and comparison between the tests.\u0000 The paper will provide a description of the test matrix and test objectives are given with the background of the previously performed OPB tests. Next a detailed description of the test rig is presented including the utilized instrumentation. Finally, an explanation of the implemented real-time test monitoring and the performed post-processing on the readings, in line with the test objectives is mentioned. The initial test results are briefly provided at the end.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85202119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper we consider the allocation problem within the context of optimal motion control for floating or submerged bodies. The purpose of our research is to develop an allocation algorithm which allows for (1) multiple bodies with up to six modes for each body, (2) arbitrary actuator types — azimuthing thrusters, propeller-rudder systems etc., (3) arbitrary objective functions, (4) interaction effects such as forbidden zones, and (5) physical limitations such as saturation. Some ideas presented in [1, 2] were generalised to more widely applicable concepts. Each body has an arbitrary number of actuators, each actuator has an arbitrary number of degrees of freedom. Interaction effects are modelled by means of state-dependent effectivity coefficients. Coupled states, such as propeller thrust and torque, are modelled as linearised constraints. The constrained optimization problem is solved with a combination of Sequential Quadratic Programming and Steepest Descent methods. The Python implementation is coupled with MARIN’s extensible modelling framework (XMF). We demonstrate the generic allocation algorithm for an underwater vehicle with multiple actuator types, physical limitations and coupled states and for a surface vessel with two propeller-rudder systems and a bow tunnel thruster. The results show that the allocation algorithm is able to handle complex configurations with specific physical limitations and coupled modes while adopting a generic approach.
{"title":"A Generic Allocation Algorithm for Optimal 6dof Motion Control Including Interaction Effects and Physical Limitations","authors":"E. Daalen","doi":"10.1115/omae2020-19185","DOIUrl":"https://doi.org/10.1115/omae2020-19185","url":null,"abstract":"\u0000 In this paper we consider the allocation problem within the context of optimal motion control for floating or submerged bodies. The purpose of our research is to develop an allocation algorithm which allows for (1) multiple bodies with up to six modes for each body, (2) arbitrary actuator types — azimuthing thrusters, propeller-rudder systems etc., (3) arbitrary objective functions, (4) interaction effects such as forbidden zones, and (5) physical limitations such as saturation.\u0000 Some ideas presented in [1, 2] were generalised to more widely applicable concepts. Each body has an arbitrary number of actuators, each actuator has an arbitrary number of degrees of freedom. Interaction effects are modelled by means of state-dependent effectivity coefficients. Coupled states, such as propeller thrust and torque, are modelled as linearised constraints. The constrained optimization problem is solved with a combination of Sequential Quadratic Programming and Steepest Descent methods.\u0000 The Python implementation is coupled with MARIN’s extensible modelling framework (XMF). We demonstrate the generic allocation algorithm for an underwater vehicle with multiple actuator types, physical limitations and coupled states and for a surface vessel with two propeller-rudder systems and a bow tunnel thruster. The results show that the allocation algorithm is able to handle complex configurations with specific physical limitations and coupled modes while adopting a generic approach.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78054642","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 conventional way to model hydrodynamic memory or radiation force is to use retardation functions. These functions are usually derived from frequency-dependent damping functions that are calculated by a diffraction-radiation code using potential theory. Calculating the retardation functions can be challenging due to lack of information at high frequency. In simulation of wave-driven vessel motion the retardation function is convolved with the velocity to give the wave radiation force, which is time-consuming. The paper describes how the memory effects can be modelled consistently by linear differential equations, such that coupled modes of motion share one set of poles. The coefficients of the differential equations are found by least squares fitting of a certain rational function to the numerical damping function. One advantage of this is that no assumption need to be made about the added mass at infinite frequency. Nor is any conditioning of the given data necessary. Using the fitted model in time-domain simulation is much quicker than using retardation functions. The method is applied to data representing the sway, roll and yaw motions of an FPSO of 238 m length. It was found that a sixth-order differential equation model fitted the given numeric radiation function well. It is shown how the high frequency asymptote for added mass can be estimated with high accuracy, which is valuable when it is not known in advance.
{"title":"Consistent State Space Modelling of Hydrodynamic Memory","authors":"K. E. Kaasen","doi":"10.1115/omae2020-19194","DOIUrl":"https://doi.org/10.1115/omae2020-19194","url":null,"abstract":"\u0000 The conventional way to model hydrodynamic memory or radiation force is to use retardation functions. These functions are usually derived from frequency-dependent damping functions that are calculated by a diffraction-radiation code using potential theory. Calculating the retardation functions can be challenging due to lack of information at high frequency. In simulation of wave-driven vessel motion the retardation function is convolved with the velocity to give the wave radiation force, which is time-consuming. The paper describes how the memory effects can be modelled consistently by linear differential equations, such that coupled modes of motion share one set of poles.\u0000 The coefficients of the differential equations are found by least squares fitting of a certain rational function to the numerical damping function. One advantage of this is that no assumption need to be made about the added mass at infinite frequency. Nor is any conditioning of the given data necessary.\u0000 Using the fitted model in time-domain simulation is much quicker than using retardation functions. The method is applied to data representing the sway, roll and yaw motions of an FPSO of 238 m length. It was found that a sixth-order differential equation model fitted the given numeric radiation function well.\u0000 It is shown how the high frequency asymptote for added mass can be estimated with high accuracy, which is valuable when it is not known in advance.","PeriodicalId":23502,"journal":{"name":"Volume 1: Offshore Technology","volume":"164 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72810767","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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