An Empirical Procedure for Fatigue Damage Estimation in Instrumented Risers

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
C. Shi ◽  
L. Manuel
Keyword(s):  
Fatigue Damage ◽  
Waveform Analysis ◽  
Damage Estimation ◽  
Response Characteristics ◽  
Empirical Procedure ◽  
Natural Modes ◽  
Spatial Modes ◽  
Few Data ◽  
Proper Orthogonal ◽  
Sensor Locations

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.

An Empirical Procedure for Fatigue Damage Estimation in Instrumented Risers

2016 ◽  
Author(s):  
C. Shi ◽  
L. Manuel
Keyword(s):  
Fatigue Damage ◽  
Waveform Analysis ◽  
Mode Shapes ◽  
Damage Estimation ◽  
Response Characteristics ◽  
Empirical Procedure ◽  
Natural Modes ◽  
Fatigue Damage Accumulation ◽  
Few Data ◽  
Sensor Locations

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.

Empirical Procedures for Long-Term Prediction of Fatigue Damage for an Instrumented Marine Riser

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
C. Shi ◽  
L. Manuel ◽  
M. A. Tognarelli
Keyword(s):  
Fatigue Damage ◽  
Field Measurements ◽  
Damage Estimation ◽  
Current Profile ◽  
Short Term ◽  
Response Characteristics ◽  
Damage Rate ◽  
Using Data ◽  
Analytical Approaches

Slender marine risers used in deepwater applications can experience vortex-induced vibration (VIV). It is becoming increasingly common for field monitoring campaigns to be undertaken wherein data loggers such as strain sensors and/or accelerometers are installed on such risers to aid in VIV-related fatigue damage estimation. Such damage estimation relies on the application of empirical procedures that make use of the collected data. This type of damage estimation can be undertaken for different current profiles encountered. The empirical techniques employed make direct use of the measurements and key components in the analyszes (such as participating riser modes selected for use in damage estimation) are intrinsically dependent on the actual current profiles. Fatigue damage predicted in this manner is in contrast to analytical approaches that rely on simplifying assumptions on both the flow conditions and the response characteristics. Empirical fatigue damage estimates conditional on current profile type can account explicitly even for complex response characteristics, participating riser modes, etc. With significant amounts of data, it is possible to establish “short-term” fatigue damage rate distributions conditional on current type. If the relative frequency of different current types is known from metocean studies, the short-term fatigue distributions can be combined with the current distributions to yield integrated “long-term” fatigue damage rate distributions. Such a study is carried out using data from the Norwegian Deepwater Programme (NDP) model riser subject to several sheared and uniform current profiles and with assumed probabilities for different current conditions. From this study, we seek to demonstrate the effectiveness of empirical techniques utilized in combination with field measurements to predict the long-term fatigue damage and the fatigue failure probability.

Empirical Procedures for Long-Term Prediction of Fatigue Damage for an Instrumented Marine Riser

2011 ◽  
Author(s):  
C. Shi ◽  
L. Manuel ◽  
M. A. Tognarelli
Keyword(s):  
Fatigue Damage ◽  
Field Measurements ◽  
Damage Estimation ◽  
Current Profile ◽  
Short Term ◽  
Response Characteristics ◽  
Damage Rate ◽  
Using Data ◽  
Analytical Approaches

Slender marine risers used in deepwater applications can experience vortex-induced vibration (VIV). It is becoming increasingly common for field monitoring campaigns to be undertaken wherein data loggers such as strain sensors and/or accelerometers are installed on such risers to aid in VIV-related fatigue damage estimation. Such damage estimation relies on the application of empirical procedures that make use of the collected data. This type of damage estimation can be undertaken for different current profiles encountered. The empirical techniques employed make direct use of the measurements and key components in the analyses (such as participating riser modes selected for use in damage estimation) are intrinsically dependent on the actual current profiles. Fatigue damage predicted in this manner is in contrast to analytical approaches that rely on simplifying assumptions on both the flow conditions and the response characteristics. Empirical fatigue damage estimates conditional on current profile type can account explicitly even for complex response characteristics, participating riser modes, etc. With significant amounts of data, it is possible to establish “short-term” fatigue damage rate distributions conditional on current type. If the relative frequency of different current types is known from metocean studies, the short-term fatigue distributions can be combined with the current distributions to yield integrated “long-term” fatigue damage rate distributions. Such a study is carried out using data from the Norwegian Deepwater Programme (NDP) model riser subject to several sheared and uniform current profiles and with assumed probabilities for different current conditions. From this study, we seek to demonstrate the effectiveness of empirical techniques utilized in combination with field measurements to predict long-term fatigue damage and life.

Alternative Empirical Procedures for Fatigue Damage Rate Estimation of Instrumented Risers Undergoing Vortex-Induced Vibration

2010 ◽  
Author(s):  
C. Shi ◽  
L. Manuel ◽  
M. A. Tognarelli
Keyword(s):  
Fatigue Damage ◽  
Waveform Analysis ◽  
Phase Reconstruction ◽  
Empirical Methods ◽  
Empirical Estimation ◽  
Flexible Cylinder ◽  
Vortex Induced Vibration ◽  
Damage Rate ◽  
Data Loggers ◽  
Proper Orthogonal

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.

scholarly journals A Comparison of Empirical Procedures for Fatigue Damage Prediction in Instrumented Risers Undergoing Vortex-Induced Vibration

2018 ◽  
Vol 8 (11) ◽  
pp. 2085 ◽  
Author(s):  
Chen Shi ◽  
Lance Manuel ◽  
Michael Tognarelli
Keyword(s):  
Fatigue Damage ◽  
Waveform Analysis ◽  
Phase Reconstruction ◽  
Empirical Methods ◽  
Empirical Estimation ◽  
Flexible Cylinder ◽  
Vortex Induced Vibration ◽  
Damage Prediction ◽  
Data Loggers ◽  
Proper Orthogonal

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.

scholarly journals A Comparison of Empirical Procedures for Fatigue Damage Prediction in Instrumented Risers undergoing Vortex-Induced Vibration

2018 ◽  
Author(s):  
Chen Shi ◽  
Lance Manuel ◽  
Michael Tognarelli
Keyword(s):  
Fatigue Damage ◽  
Waveform Analysis ◽  
Phase Reconstruction ◽  
Empirical Methods ◽  
Empirical Estimation ◽  
Flexible Cylinder ◽  
Vortex Induced Vibration ◽  
Damage Prediction ◽  
Data Loggers ◽  
Proper Orthogonal

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.

Spectral analysis of sine-sweep vibration: A fatigue damage estimation method

2021 ◽  
Vol 157 ◽  
pp. 107698
Author(s):  
M. Palmieri ◽  
F. Cianetti ◽  
G. Zucca ◽  
G. Morettini ◽  
C. Braccesi
Keyword(s):  
Spectral Analysis ◽  
Fatigue Damage ◽  
Estimation Method ◽  
Damage Estimation ◽  
Sine Sweep

Inverse design of aircraft cabin environment using computational fluid dynamics-based proper orthogonal decomposition method

2017 ◽  
Vol 27 (10) ◽  
pp. 1379-1391 ◽  
Author(s):  
Jihong Wang ◽  
Tengfei (Tim) Zhang ◽  
Hongbiao Zhou ◽  
Shugang Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Proper Orthogonal Decomposition ◽  
Flow Fields ◽  
Orthogonal Decomposition ◽  
Inverse Design ◽  
Air Supply ◽  
Spatial Modes ◽  
Cabin Environment ◽  
Proper Orthogonal

To design a comfortable aircraft cabin environment, designers conventionally follow an iterative guess-and-correction procedure to determine the air-supply parameters. The conventional method has an extremely low efficiency but does not guarantee an optimal design. This investigation proposed an inverse design method based on a proper orthogonal decomposition of the thermo-flow data provided by full computational fluid dynamics simulations. The orthogonal spatial modes of the thermo-flow fields and corresponding coefficients were firstly extracted. Then, a thermo-flow field was expressed into a linear combination of the spatial modes with their coefficients. The coefficients for each spatial mode are functions of air-supply parameters, which can be interpolated. With a quick map of the cause–effect relationship between the air-supply parameters and the exhibited thermo-flow fields, the optimal air-supply parameters were determined from specific design targets. By setting the percentage of dissatisfied and the predicted mean vote as design targets, the proposed method was implemented for inverse determination of air-supply parameters in two aircraft cabins. The results show that the inverse design using computational fluid dynamics-based proper orthogonal decomposition method is viable. Most of computing time lies in the construction of data samples of thermo-flow fields, while the proper orthogonal decomposition analysis and data interpolation is efficient.

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