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Michael Tognarelli - One of the best experts on this subject based on the ideXlab platform.
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A Comparison of Empirical Procedures for Fatigue Damage Prediction in Instrumented Risers undergoing Vortex-Induced Vibration
2018Co-Authors: C. Shi, Lance Manuel, Michael TognarelliAbstract:To gain insight into Riser motions and associated fatigue damage due to vortex-induced vibration (VIV), data loggers such as strain sensors and/or accelerometers are sometimes deployed on Risers to monitor their motion in different current velocity conditions. Accurate reconstruction of the Riser response and empirical estimation of fatigue damage rates over the entire Riser Length using measurements from a limited number of sensors can help in efficient utilization of the costly measurements recorded. Several different empirical procedures are described here for analysis of the VIV response of a long flexible cylinder subjected to uniform and sheared current profiles. The methods include weighted waveform analysis (WWA), proper orthogonal decomposition (POD), modal phase reconstruction (MPR), a modified WWA procedure, and a hybrid method which combines MPR and the modified WWA method. Fatigue damage rates estimated using these different empirical methods are compared and cross-validated against measurements. Detailed formulations for each method are presented and discussed with examples. Results suggest that all the empirical methods, despite different underlying assumptions in each of them, can be employed to estimate fatigue damage rates quite well from limited strain measurements.
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A Data-Driven Mode Identification Algorithm for Riser Fatigue Damage Assessment
Journal of Offshore Mechanics and Arctic Engineering, 2014Co-Authors: C. Shi, Lance Manuel, Jinkyoo Park, Michael TognarelliAbstract:A well-established empirical procedure, which we refer to as weighted waveform analysis (WWA), is employed to reconstruct a model Riser's response over its entire Length using a limited number of strain measurements. The quality of the response reconstruction is controlled largely by identification of the participating Riser response modes (waveforms); hence, mode selection is vital in WWA application. Instead of selecting a set of consecutive Riser vibratory modes, we propose a procedure that automatically identifies a set of nonconsecutive Riser modes that can thus account for higher harmonics in the Riser response (at multiplies of the Strouhal frequency). Using temporal data analysis of the discrete time-stamped samples, significant response frequencies are identified on the basis of power spectrum peaks; similarly, using the spatial data analysis of the sparse nonuniformly sampled data, significant wavenumbers are identified using Lomb–Scargle periodograms. Knowing the Riser Length, the most important wavenumber is related to a specific mode number; this dominant mode is, in turn, related to the dominant peak in power spectra based on the temporal data analysis. The Riser's fundamental frequency is estimated as the ratio of the empirically estimated dominant spectral frequency to the dominant mode number. Additional mode numbers are also identified as spectral peak frequencies divided by the fundamental frequency. This mode selection technique is an improvement over similar WWA procedures that rely on a priori knowledge of the Riser's fundamental frequency or on the knowledge of the physical properties and assumptions on added mass contributions. At selected target locations, we compare fatigue damage rates, estimated based on the Riser response reconstructed using the WWA method with the proposed automated mode selection technique (we refer to this as the “improved” WWA) and those based on the “original” WWA method (that relies on a theoretically computed fundamental natural frequency of the Riser). In both cases, predicted fatigue damage rates based on the empirical methods and data at various locations (other than the target) are cross-validated against damage rates based directly on measurements at the target location. The results show that the improved WWA method, which empirically estimates the Riser's fundamental natural frequency and automatically selects significant modes of vibration, may be employed to estimate fatigue damage rates quite well from limited strain measurements.
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a data driven mode identification algorithm for fatigue damage assessment in instrumented marine Risers
ASME 2011 30th International Conference on Ocean Offshore and Arctic Engineering OMAE2011, 2011Co-Authors: Jinkyoo Park, Lance Manuel, Michael TognarelliAbstract:A well-established empirical procedure, which we refer to as Weighted Waveform Analysis (WWA), is employed to reconstruct a model Riser’s response over its entire Length using a limited number of strain measurements. The quality of the response reconstruction is controlled largely by identification of the participating Riser response modes (waveforms); hence, mode selection is vital in WWA application. Instead of selecting a set of consecutive Riser vibratory modes, we propose a procedure that automatically identifies a set of non-consecutive Riser modes that can thus account for higher harmonics in the Riser response (at multiplies of the Strouhal frequency). Using temporal data analysis of the discrete time-stamped samples, significant response frequencies are identified on the basis of power spectrum peaks; similarly using spatial data analysis of the sparse non-uniformly sampled data, significant wavenumbers are identified using Lomb-Scargle periodograms. Knowing the Riser Length, the most important wavenumber is related to a specific mode number; this dominant mode is in turn related to the dominant peak in power spectra based on the temporal data analysis. The Riser’s fundamental frequency is estimated as the ratio of the empirically estimated dominant spectral frequency to the dominant mode number. Additional mode numbers are also identified as spectral peak frequencies divided by the fundamental frequency. This mode selection technique is an improvement over similar WWA procedures that rely on a priori knowledge of the Risers fundamental frequency or on knowledge of physical properties and assumptions on added mass contributions. At selected target locations, we compare fatigue damage rates, estimated based on the Riser response reconstructed using the WWA method with the proposed automated mode selection technique (we refer to this as “improved” WWA) and those based on the “original” WWA method (that relies on a theoretically computed fundamental natural frequency of the Riser). In both cases, predicted fatigue damage rates based on the empirical methods and data at various locations (other than the target) are cross-validated against damage rates based directly on measurements at the target location. Results show that the improved WWA method, which empirically estimates the Riser’s fundamental natural frequency and automatically selects significant modes of vibration, may be employed to estimate fatigue damage rates quite well from limited strain measurements.Copyright © 2011 by ASME
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on the vortex induced vibration response of a model Riser and location of sensors for fatigue damage prediction
ASME 2010 29th International Conference on Ocean Offshore and Arctic Engineering OMAE2010, 2010Co-Authors: Lance Manuel, Michael Tognarelli, T BotrosAbstract:This study is concerned with vortex-induced vibration (VIV) of deepwater marine Risers. Riser response measurements from model tests on a densely instrumented long, flexible Riser in uniform and sheared currents offer an almost ideal set-up for our work. Our objectives are two-fold: (i) we use the measured data to describe complexities inherent in Riser motions accompanying VIV; and (ii) we discuss how such data sets (and even less spatially dense monitoring) can be used effectively in predicting fatigue damage rates which is of critical interest for deepwater Risers. First, we use mathematical tools including Hilbert and wavelet transforms to estimate instantaneous amplitudes and phases of cross-flow (CF) and in-line (IL) displacements for the model Riser as well as scalograms to understand time-frequency characteristics of the response; this work confirms that the motion of a long flexible cylinder is far more complex than that of a rigid cylinder, and that non-stationary characteristics, higher harmonics, and traveling waves are evident in the Riser response. Second, a well-established empirical procedure, which we refer to as Weighted Waveform Analysis (WWA), is employed to estimate the fatigue damage rate at various locations along the Length of the Riser from strain measurements at only eight sensors. By iterating over numerous different combinations of these eight strain sensors as inputs (from among all the twenty-four available locations on the Riser), optimal locations for the eight sensors on the Riser are identified by cross-validation, whereby predicted strains and fatigue damage rates at locations of instrumented sensors are compared with strains and fatigue damage rates based on actual recorded measurements there. We find that, if properly placed, as few as eight sensors can provide reasonably accurate estimates of the fatigue damage rate over the entire Riser Length. Finally, we demonstrate how more accurate fatigue damage prediction can result when non-stationary response characteristics are considered and a modified WWA method (that more effectively accounts for traveling waves than the WWA method alone does) is employed.Copyright © 2010 by ASME
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Alternative empirical procedures for fatigue damage rate estimation of instrumented Risers undergoing vortex-induced vibration
29th International Conference on Ocean Offshore and Arctic Engineering: Volume 6, 2010Co-Authors: C. Shi, Lance Manuel, Michael TognarelliAbstract:Vortex-induced vibration (VIV) is a topic of great importance in fatigue damage assessment and life prediction for marine Risers. In order to gain insight into Riser motions and estimated fatigue damage due to VIV, data loggers such as strain sensors and/or accelerometers are sometimes installed on Risers to monitor their motion in different current velocity conditions. Accurate reconstruction of the Riser response and empirical estimation of fatigue damage rates over the entire Riser Length using measurements from a limited number of sensors is important for efficient utilization of the costly measurements recorded. In this study, different empirical methods are employed to analyze the VIV response of a long flexible cylinder subjected to uniform and sheared current profiles. The methods include weighted waveform analysis (WWA), proper orthogonal decomposition (POD), modal phase reconstruction (MPR), a modified WWA procedure, and a hybrid method which combines MPR and the modified WWA method. Fatigue damage rates estimated using these different empirical methods are compared and cross-validated against measurements. Formulations for each method are briefly presented and discussed with examples. Results show that all the empirical methods, despite different underlying assumptions in each of them, can be employed to estimate fatigue damage rates quite well from limited strain measurements.Copyright © 2010 by ASME
Lance Manuel - One of the best experts on this subject based on the ideXlab platform.
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A Comparison of Empirical Procedures for Fatigue Damage Prediction in Instrumented Risers undergoing Vortex-Induced Vibration
2018Co-Authors: C. Shi, Lance Manuel, Michael TognarelliAbstract:To gain insight into Riser motions and associated fatigue damage due to vortex-induced vibration (VIV), data loggers such as strain sensors and/or accelerometers are sometimes deployed on Risers to monitor their motion in different current velocity conditions. Accurate reconstruction of the Riser response and empirical estimation of fatigue damage rates over the entire Riser Length using measurements from a limited number of sensors can help in efficient utilization of the costly measurements recorded. Several different empirical procedures are described here for analysis of the VIV response of a long flexible cylinder subjected to uniform and sheared current profiles. The methods include weighted waveform analysis (WWA), proper orthogonal decomposition (POD), modal phase reconstruction (MPR), a modified WWA procedure, and a hybrid method which combines MPR and the modified WWA method. Fatigue damage rates estimated using these different empirical methods are compared and cross-validated against measurements. Detailed formulations for each method are presented and discussed with examples. Results suggest that all the empirical methods, despite different underlying assumptions in each of them, can be employed to estimate fatigue damage rates quite well from limited strain measurements.
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An Empirical Procedure for Fatigue Damage Estimation in Instrumented Risers
Journal of Offshore Mechanics and Arctic Engineering, 2017Co-Authors: C. Shi, Lance ManuelAbstract:In order to assess the effects of vortex-induced vibration (VIV) and to ensure Riser integrity, field monitoring campaigns are often conducted wherein the Riser response is recorded by a few data sensors distributed along the Length of the Riser. In this study, two empirical techniques–proper orthogonal decomposition (POD) and weighted waveform analysis (WWA)–are sequentially applied to the data; together, they offer a novel empirical procedure for fatigue damage estimation in an instrumented Riser. The procedures are briefly described as follows: first, POD is used to extract the most energetic spatial modes of the Riser response from the measurements, which are defined only at the available sensor locations. Accordingly, a second step uses WWA to express each dominant POD mode as a series of Riser natural modes that are continuous spatial functions defined over the entire Riser Length. Based on the above empirically identified modal information, the Riser response over the entire Length is reconstructed in reverse–i.e., compose identified natural modes into the POD modes and, then, assemble all these dominant POD modal response components into the derived Riser response. The POD procedure empirically extracts the energetic dynamic response characteristics without any assumptions and effectively cleans the data of noisy or less important features; this fundamental application of WWA is used to identify dominant Riser natural modes–all this is possible using the limited number of available measurements from sensor locations. Application of the procedure is demonstrated using experimental data from the Norwegian Deepwater Programme (NDP) model Riser.
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An Empirical Procedure for Fatigue Damage Estimation in Instrumented Risers
Volume 2: CFD and VIV, 2016Co-Authors: C. Shi, Lance ManuelAbstract:Vortex-induced vibration (VIV) can lead to significant fatigue damage accumulation in deepwater marine Risers. In order to assess the effects of VIV and to ensure Riser integrity, field monitoring campaigns are often conducted wherein Riser response is recorded by a few data sensors distributed along the Length of the Riser. It is possible to empirically estimate the fatigue damage at “key” critical fatigue-sensitive locations, where sensors may not be available as part of the spatially distributed discrete measurements. In this study, two empirical techniques — Proper Orthogonal Decomposition (POD) and Weighted Waveform Analysis (WWA) — are sequentially applied to the data; together, they offer a novel empirical procedure for fatigue damage estimation in an instrumented Riser. The procedures are briefly described as follows: first, POD is used to extract the most energetic spatial modes of the Riser response from the measurements. Often, only a few dominant POD modes preserve most of the Riser motion kinetic energy; other modes are less important. Identified POD mode shapes are discrete as they are defined only at the available sensor locations. Accordingly, a second step in the proposed procedure uses WWA to express each dominant POD mode as a series of Riser natural modes that are continuous spatial functions defined over the entire Riser Length. Based on the above empirically identified modal information, the Riser response over the entire Length is reconstructed using backward procedures — i.e., compose identified natural modes into the POD modes and, then, assemble all these dominant POD modal response components into the derived Riser response. The POD procedure empirically extracts the energetic dynamic response characteristics without any assumptions and effectively cleans the data of noisy or less important features, which makes it possible for WWA to identify dominant Riser natural modes — all this is possible using the limited number of available measurements from sensor locations. Application of the entire procedure is demonstrated using experimental data from the Norwegian Deepwater Programme (NDP) model Riser.
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A Data-Driven Mode Identification Algorithm for Riser Fatigue Damage Assessment
Journal of Offshore Mechanics and Arctic Engineering, 2014Co-Authors: C. Shi, Lance Manuel, Jinkyoo Park, Michael TognarelliAbstract:A well-established empirical procedure, which we refer to as weighted waveform analysis (WWA), is employed to reconstruct a model Riser's response over its entire Length using a limited number of strain measurements. The quality of the response reconstruction is controlled largely by identification of the participating Riser response modes (waveforms); hence, mode selection is vital in WWA application. Instead of selecting a set of consecutive Riser vibratory modes, we propose a procedure that automatically identifies a set of nonconsecutive Riser modes that can thus account for higher harmonics in the Riser response (at multiplies of the Strouhal frequency). Using temporal data analysis of the discrete time-stamped samples, significant response frequencies are identified on the basis of power spectrum peaks; similarly, using the spatial data analysis of the sparse nonuniformly sampled data, significant wavenumbers are identified using Lomb–Scargle periodograms. Knowing the Riser Length, the most important wavenumber is related to a specific mode number; this dominant mode is, in turn, related to the dominant peak in power spectra based on the temporal data analysis. The Riser's fundamental frequency is estimated as the ratio of the empirically estimated dominant spectral frequency to the dominant mode number. Additional mode numbers are also identified as spectral peak frequencies divided by the fundamental frequency. This mode selection technique is an improvement over similar WWA procedures that rely on a priori knowledge of the Riser's fundamental frequency or on the knowledge of the physical properties and assumptions on added mass contributions. At selected target locations, we compare fatigue damage rates, estimated based on the Riser response reconstructed using the WWA method with the proposed automated mode selection technique (we refer to this as the “improved” WWA) and those based on the “original” WWA method (that relies on a theoretically computed fundamental natural frequency of the Riser). In both cases, predicted fatigue damage rates based on the empirical methods and data at various locations (other than the target) are cross-validated against damage rates based directly on measurements at the target location. The results show that the improved WWA method, which empirically estimates the Riser's fundamental natural frequency and automatically selects significant modes of vibration, may be employed to estimate fatigue damage rates quite well from limited strain measurements.
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a data driven mode identification algorithm for fatigue damage assessment in instrumented marine Risers
ASME 2011 30th International Conference on Ocean Offshore and Arctic Engineering OMAE2011, 2011Co-Authors: Jinkyoo Park, Lance Manuel, Michael TognarelliAbstract:A well-established empirical procedure, which we refer to as Weighted Waveform Analysis (WWA), is employed to reconstruct a model Riser’s response over its entire Length using a limited number of strain measurements. The quality of the response reconstruction is controlled largely by identification of the participating Riser response modes (waveforms); hence, mode selection is vital in WWA application. Instead of selecting a set of consecutive Riser vibratory modes, we propose a procedure that automatically identifies a set of non-consecutive Riser modes that can thus account for higher harmonics in the Riser response (at multiplies of the Strouhal frequency). Using temporal data analysis of the discrete time-stamped samples, significant response frequencies are identified on the basis of power spectrum peaks; similarly using spatial data analysis of the sparse non-uniformly sampled data, significant wavenumbers are identified using Lomb-Scargle periodograms. Knowing the Riser Length, the most important wavenumber is related to a specific mode number; this dominant mode is in turn related to the dominant peak in power spectra based on the temporal data analysis. The Riser’s fundamental frequency is estimated as the ratio of the empirically estimated dominant spectral frequency to the dominant mode number. Additional mode numbers are also identified as spectral peak frequencies divided by the fundamental frequency. This mode selection technique is an improvement over similar WWA procedures that rely on a priori knowledge of the Risers fundamental frequency or on knowledge of physical properties and assumptions on added mass contributions. At selected target locations, we compare fatigue damage rates, estimated based on the Riser response reconstructed using the WWA method with the proposed automated mode selection technique (we refer to this as “improved” WWA) and those based on the “original” WWA method (that relies on a theoretically computed fundamental natural frequency of the Riser). In both cases, predicted fatigue damage rates based on the empirical methods and data at various locations (other than the target) are cross-validated against damage rates based directly on measurements at the target location. Results show that the improved WWA method, which empirically estimates the Riser’s fundamental natural frequency and automatically selects significant modes of vibration, may be employed to estimate fatigue damage rates quite well from limited strain measurements.Copyright © 2011 by ASME
C. Shi - One of the best experts on this subject based on the ideXlab platform.
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A Comparison of Empirical Procedures for Fatigue Damage Prediction in Instrumented Risers undergoing Vortex-Induced Vibration
2018Co-Authors: C. Shi, Lance Manuel, Michael TognarelliAbstract:To gain insight into Riser motions and associated fatigue damage due to vortex-induced vibration (VIV), data loggers such as strain sensors and/or accelerometers are sometimes deployed on Risers to monitor their motion in different current velocity conditions. Accurate reconstruction of the Riser response and empirical estimation of fatigue damage rates over the entire Riser Length using measurements from a limited number of sensors can help in efficient utilization of the costly measurements recorded. Several different empirical procedures are described here for analysis of the VIV response of a long flexible cylinder subjected to uniform and sheared current profiles. The methods include weighted waveform analysis (WWA), proper orthogonal decomposition (POD), modal phase reconstruction (MPR), a modified WWA procedure, and a hybrid method which combines MPR and the modified WWA method. Fatigue damage rates estimated using these different empirical methods are compared and cross-validated against measurements. Detailed formulations for each method are presented and discussed with examples. Results suggest that all the empirical methods, despite different underlying assumptions in each of them, can be employed to estimate fatigue damage rates quite well from limited strain measurements.
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An Empirical Procedure for Fatigue Damage Estimation in Instrumented Risers
Journal of Offshore Mechanics and Arctic Engineering, 2017Co-Authors: C. Shi, Lance ManuelAbstract:In order to assess the effects of vortex-induced vibration (VIV) and to ensure Riser integrity, field monitoring campaigns are often conducted wherein the Riser response is recorded by a few data sensors distributed along the Length of the Riser. In this study, two empirical techniques–proper orthogonal decomposition (POD) and weighted waveform analysis (WWA)–are sequentially applied to the data; together, they offer a novel empirical procedure for fatigue damage estimation in an instrumented Riser. The procedures are briefly described as follows: first, POD is used to extract the most energetic spatial modes of the Riser response from the measurements, which are defined only at the available sensor locations. Accordingly, a second step uses WWA to express each dominant POD mode as a series of Riser natural modes that are continuous spatial functions defined over the entire Riser Length. Based on the above empirically identified modal information, the Riser response over the entire Length is reconstructed in reverse–i.e., compose identified natural modes into the POD modes and, then, assemble all these dominant POD modal response components into the derived Riser response. The POD procedure empirically extracts the energetic dynamic response characteristics without any assumptions and effectively cleans the data of noisy or less important features; this fundamental application of WWA is used to identify dominant Riser natural modes–all this is possible using the limited number of available measurements from sensor locations. Application of the procedure is demonstrated using experimental data from the Norwegian Deepwater Programme (NDP) model Riser.
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An Empirical Procedure for Fatigue Damage Estimation in Instrumented Risers
Volume 2: CFD and VIV, 2016Co-Authors: C. Shi, Lance ManuelAbstract:Vortex-induced vibration (VIV) can lead to significant fatigue damage accumulation in deepwater marine Risers. In order to assess the effects of VIV and to ensure Riser integrity, field monitoring campaigns are often conducted wherein Riser response is recorded by a few data sensors distributed along the Length of the Riser. It is possible to empirically estimate the fatigue damage at “key” critical fatigue-sensitive locations, where sensors may not be available as part of the spatially distributed discrete measurements. In this study, two empirical techniques — Proper Orthogonal Decomposition (POD) and Weighted Waveform Analysis (WWA) — are sequentially applied to the data; together, they offer a novel empirical procedure for fatigue damage estimation in an instrumented Riser. The procedures are briefly described as follows: first, POD is used to extract the most energetic spatial modes of the Riser response from the measurements. Often, only a few dominant POD modes preserve most of the Riser motion kinetic energy; other modes are less important. Identified POD mode shapes are discrete as they are defined only at the available sensor locations. Accordingly, a second step in the proposed procedure uses WWA to express each dominant POD mode as a series of Riser natural modes that are continuous spatial functions defined over the entire Riser Length. Based on the above empirically identified modal information, the Riser response over the entire Length is reconstructed using backward procedures — i.e., compose identified natural modes into the POD modes and, then, assemble all these dominant POD modal response components into the derived Riser response. The POD procedure empirically extracts the energetic dynamic response characteristics without any assumptions and effectively cleans the data of noisy or less important features, which makes it possible for WWA to identify dominant Riser natural modes — all this is possible using the limited number of available measurements from sensor locations. Application of the entire procedure is demonstrated using experimental data from the Norwegian Deepwater Programme (NDP) model Riser.
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A Data-Driven Mode Identification Algorithm for Riser Fatigue Damage Assessment
Journal of Offshore Mechanics and Arctic Engineering, 2014Co-Authors: C. Shi, Lance Manuel, Jinkyoo Park, Michael TognarelliAbstract:A well-established empirical procedure, which we refer to as weighted waveform analysis (WWA), is employed to reconstruct a model Riser's response over its entire Length using a limited number of strain measurements. The quality of the response reconstruction is controlled largely by identification of the participating Riser response modes (waveforms); hence, mode selection is vital in WWA application. Instead of selecting a set of consecutive Riser vibratory modes, we propose a procedure that automatically identifies a set of nonconsecutive Riser modes that can thus account for higher harmonics in the Riser response (at multiplies of the Strouhal frequency). Using temporal data analysis of the discrete time-stamped samples, significant response frequencies are identified on the basis of power spectrum peaks; similarly, using the spatial data analysis of the sparse nonuniformly sampled data, significant wavenumbers are identified using Lomb–Scargle periodograms. Knowing the Riser Length, the most important wavenumber is related to a specific mode number; this dominant mode is, in turn, related to the dominant peak in power spectra based on the temporal data analysis. The Riser's fundamental frequency is estimated as the ratio of the empirically estimated dominant spectral frequency to the dominant mode number. Additional mode numbers are also identified as spectral peak frequencies divided by the fundamental frequency. This mode selection technique is an improvement over similar WWA procedures that rely on a priori knowledge of the Riser's fundamental frequency or on the knowledge of the physical properties and assumptions on added mass contributions. At selected target locations, we compare fatigue damage rates, estimated based on the Riser response reconstructed using the WWA method with the proposed automated mode selection technique (we refer to this as the “improved” WWA) and those based on the “original” WWA method (that relies on a theoretically computed fundamental natural frequency of the Riser). In both cases, predicted fatigue damage rates based on the empirical methods and data at various locations (other than the target) are cross-validated against damage rates based directly on measurements at the target location. The results show that the improved WWA method, which empirically estimates the Riser's fundamental natural frequency and automatically selects significant modes of vibration, may be employed to estimate fatigue damage rates quite well from limited strain measurements.
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Alternative empirical procedures for fatigue damage rate estimation of instrumented Risers undergoing vortex-induced vibration
29th International Conference on Ocean Offshore and Arctic Engineering: Volume 6, 2010Co-Authors: C. Shi, Lance Manuel, Michael TognarelliAbstract:Vortex-induced vibration (VIV) is a topic of great importance in fatigue damage assessment and life prediction for marine Risers. In order to gain insight into Riser motions and estimated fatigue damage due to VIV, data loggers such as strain sensors and/or accelerometers are sometimes installed on Risers to monitor their motion in different current velocity conditions. Accurate reconstruction of the Riser response and empirical estimation of fatigue damage rates over the entire Riser Length using measurements from a limited number of sensors is important for efficient utilization of the costly measurements recorded. In this study, different empirical methods are employed to analyze the VIV response of a long flexible cylinder subjected to uniform and sheared current profiles. The methods include weighted waveform analysis (WWA), proper orthogonal decomposition (POD), modal phase reconstruction (MPR), a modified WWA procedure, and a hybrid method which combines MPR and the modified WWA method. Fatigue damage rates estimated using these different empirical methods are compared and cross-validated against measurements. Formulations for each method are briefly presented and discussed with examples. Results show that all the empirical methods, despite different underlying assumptions in each of them, can be employed to estimate fatigue damage rates quite well from limited strain measurements.Copyright © 2010 by ASME
Celso Kazuyuki Morooka - One of the best experts on this subject based on the ideXlab platform.
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experiments with a steel catenary Riser model in a towing tank
Applied Ocean Research, 2013Co-Authors: Celso Kazuyuki Morooka, Raphael I TsukadaAbstract:Abstract A model test with a steel catenary Riser (SCR) was conducted in a towing tank. The main purpose of the experiment was to gain further understanding of the global SCR dynamic behavior with vortex-induced vibration (VIV). To this end, a large model scale factor (250) was considered. The mass and stiffness of the Riser model are very low, and the Reynolds number in the experiment ranged from 400 to 600. The experimental results demonstrated the influence of traveling waves on the cross-flow response of the Riser model, which was verified by several analytical methods. This study provided important indications that the sources of the traveling waves (power-in regions) seem to change position along the Riser Length over time. Finally, the experimental design, data processing procedure, experimental set-up, and results are described in detail.
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Dynamic Behavior Analysis of a Deepwater Self Standing Hybrid Riser System
Volume 4: Offshore Geotechnics; Ronald W. Yeung Honoring Symposium on Offshore and Ship Hydrodynamics, 2012Co-Authors: Celso Kazuyuki Morooka, Denis A. ShiguemotoAbstract:Self Standing Hybrid Riser (SSHR) system is an attractive option for deepwater application. The system is composed by a vertical Riser pipe coming from the sea bottom to a subsurface buoy which is placed in around one hundred meter water depth from the sea surface. It is connected to a floating production facility at the sea surface by a flexible jumper. It almost eliminates all the undesired dynamic effects from ocean waves, in addition to relief the total Riser system weight from the floating platform. Recent discoveries of petroleum in ultra-deep water Pre-salt Offshore Brazil stimulated development of innovative and nontraditional Riser system configurations.The present work deals with the dynamic behavior of a SSHR system excited by sea current, waves and displacements induced by sea surface platform motions. In plane and out of plane displacements for the SSHR system is analyzed and subsurface buoy maximum motions amplitude have been observed. Effects from current drag and vortex induced forces are investigated by numerical simulations of the dynamic behavior of the SSHR system.Analysis procedure is presented with details, and fundamentals of the semi-empirical approach for hydrodynamic drag and vortex induced forces in the Riser Length and subsurface buoy are described. Numerical simulation results are presented, and evaluations are conducted for deepwater condition. Maximum amplitude of vibration is observed near from to lock-in conditions, and effects of the subsurface buoy vortex induced motion (VIM) are discussed. Hydrodynamic forces previously obtained from reduced model tests are used for the numerical approach.Copyright © 2012 by ASME
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Dynamic Behavior of a Vertical Riser and Service Life Reduction
24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 1 Parts A and B, 2005Co-Authors: Celso Kazuyuki Morooka, José Alfredo Ferrari, Elton J. B. Ribeiro, Fabio M. Coelho, Ricardo FrancissAbstract:In the last years, the most of offshore oil and gas reserves discoveries in Brazil are placed in ultra-deep water depths. Petroleum production from these offshore fields needs developments with novel solutions in terms of necessary technologies and economical viability. The use of vertical rigid Risers such as top tensioned Risers (TTR) and others like combined systems as self standing hybrid Risers and steel catenary Risers for ultra-deep waters have shown viable from both, technical and economical aspects. However, there are needs for detailed studies on their dynamic behavior in order to improve, particularly, the understanding of influence of the environment as wave and current, and floating platform oscillations at the Riser top. The present work presents studies on vertical top tensioned Riser dynamic behavior through time domain simulations of its displacements and respective, bending moments and stresses. Influences of the vortex induced vibrations (VIV) and waves on the Riser service life reduction are analyzed. Maximum and minimum envelops for displacements and stresses along Riser Length are shown.Copyright © 2005 by ASME
Helge Heitmann - One of the best experts on this subject based on the ideXlab platform.
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Simulation of steady flow of natural gas in a subsea flexible Riser with heat exchange
Journal of Natural Gas Science and Engineering, 2017Co-Authors: Navid Pouladi, Helge HeitmannAbstract:Abstract Flexible Riser technology is widely used in today's offshore industry. Evaluating pressure, temperature and velocity profiles in a subsea Riser or a flexible pipe is essential in the design of a gas transfer system. Conventional pipeline correlations fail to give an acceptable accuracy for sizing, design and flow assurance applications of flexibles. Hence, availability of a rather simple computational model, which can give results with acceptable accuracy is highly advantageous. The aim of this article is to present a simple numerical method which can be used efficiently to accomplish this goal. A one dimensional finite difference method is used where the Riser Length is discretized into small segments. Natural gas physical and transport properties are calculated in each segment and flow equations in addition to a state equation are solved simultaneously to find the velocity, pressure and temperature profiles in the flexible Riser. The Lee-Kesler corresponding states EOS has been used as the state equation. Mathcad™ has been applied for solving equations. The ability of the model to predict thermodynamic properties of natural gas has been compared with experimental data. Furthermore, friction and heat transfer models for a smooth and rough bore Riser have been analyzed. For a rough bore Riser with carcass corrugations, selecting a reasonable value for the equivalent sand grain roughness has been found to be crucial. The authors have also found the Joule-Thomson effect to be decisive in temperature change for a high pressure rough bore flexible gas Riser subject to high pressure drop.
