The Experts below are selected from a list of 184284 Experts worldwide ranked by ideXlab platform
Jungao Wang - One of the best experts on this subject based on the ideXlab platform.
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evaluation of vortex induced vibration of a steel catenary riser in steady current and vessel motion induced oscillatory current
Journal of Fluids and Structures, 2018Co-Authors: Shixiao Fu, Jungao Wang, Rolf BaarholmAbstract:Abstract A large-Scale Model Test of a truncated steel catenary riser (SCR) was performed in an ocean basin to investigate the riser responses under pure steady uniform current and pure vessel motions separately. Out-of-plane vortex-induced vibration (VIV) was confirmed to have occurred under both Test conditions. A comparative analysis and discussion were carried out on selected cases in terms of out-of-plane VIV responses, VIV developing mechanisms and the fatigue damage contribution. Results indicate that both steady current-induced and vessel motion-induced VIV responses are dominated by strong travelling waves, but vessel motion-induced VIV responses are more ‘intermittent’ with respect to the response amplitude and frequency owing to its space- and time-varying shedding frequency. ‘Power-in’ regions are further estimated to understand the VIV developing mechanisms for both Test conditions. Finally, fatigue damages are evaluated showing the damage by vessel motion-induced VIV is comparable and at the same level as uniform current-induced VIV, which highlights the great importance of vessel motion-induced VIV, which cannot be neglected in the design and analysis for SCR systems.
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Experimental investigation on the dynamic responses of a free-hanging water intake riser under vessel motion
Marine Structures, 2016Co-Authors: Jungao Wang, Sherry Xiang, Peimin Cao, Jianmin YangAbstract:Abstract A large-Scale Model Test of a free-hanging water intake riser (WIR) is performed in an ocean basin to investigate the riser responses under vessel motion. Top end of the WIR is forced to oscillate at given vessel motion trajectories. Fiber Brag Grating (FBG) strain sensors are used to measure the WIR dynamic responses. Experimental results firstly confirms that the free-hanging WIR would experience out-of-plane vortex-induced vibrations (VIVs) under pure vessel motion even for the case with a KC number as low as 5. Meanwhile, comparison between numerical results and experimental measurements suggests a significant drag amplification by out-of-plane vessel motion-induced VIV. What’s more, further study on WIR response frequencies and cross section trajectories reveals a strong correlation between vessel motion-induced VIV and local KC number distribution, owing to the small KC number effect. The presented work provides useful references for gaining a better understanding on VIV induced by vessel motion, and for the development of future prediction Models.
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out of plane vortex induced vibration of a steel catenary riser caused by vessel motions
Ocean Engineering, 2015Co-Authors: Jungao Wang, Shixiao Fu, Rolf Baarholm, Jie Wu, Carl M LarsenAbstract:A large-Scale Model Test of a truncated steel catenary riser (SCR) was performed in an ocean basin to investigate the riser responses under top vessel motion. Top end of the Model was forced to oscillate at given motion trajectories, corresponded with the motion at the truncation point of a full-length SCR under vessel motion. Out-of-plane vortex-induced vibration (VIV) was confirmed under pure top vessel motions, characterized with distinctive time-varying features. Results further indicate that vessel motion-induced VIV was strongly dependent on the KC number and the instantaneous equivalent flow profile. Meanwhile, tension variation was found to be another key factor causing response discrepancy between the ‘lift-up’ and ‘push-down’ phase for the large top vessel motion case. Finally, the relationship between the out-of-plane VIV dominant response frequency, maximum equivalent flow velocity and KC number were unveiled, which provides references for future vessel motion-induced VIV predictions.
Rolf Baarholm - One of the best experts on this subject based on the ideXlab platform.
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evaluation of vortex induced vibration of a steel catenary riser in steady current and vessel motion induced oscillatory current
Journal of Fluids and Structures, 2018Co-Authors: Shixiao Fu, Jungao Wang, Rolf BaarholmAbstract:Abstract A large-Scale Model Test of a truncated steel catenary riser (SCR) was performed in an ocean basin to investigate the riser responses under pure steady uniform current and pure vessel motions separately. Out-of-plane vortex-induced vibration (VIV) was confirmed to have occurred under both Test conditions. A comparative analysis and discussion were carried out on selected cases in terms of out-of-plane VIV responses, VIV developing mechanisms and the fatigue damage contribution. Results indicate that both steady current-induced and vessel motion-induced VIV responses are dominated by strong travelling waves, but vessel motion-induced VIV responses are more ‘intermittent’ with respect to the response amplitude and frequency owing to its space- and time-varying shedding frequency. ‘Power-in’ regions are further estimated to understand the VIV developing mechanisms for both Test conditions. Finally, fatigue damages are evaluated showing the damage by vessel motion-induced VIV is comparable and at the same level as uniform current-induced VIV, which highlights the great importance of vessel motion-induced VIV, which cannot be neglected in the design and analysis for SCR systems.
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out of plane vortex induced vibration of a steel catenary riser caused by vessel motions
Ocean Engineering, 2015Co-Authors: Jungao Wang, Shixiao Fu, Rolf Baarholm, Jie Wu, Carl M LarsenAbstract:A large-Scale Model Test of a truncated steel catenary riser (SCR) was performed in an ocean basin to investigate the riser responses under top vessel motion. Top end of the Model was forced to oscillate at given motion trajectories, corresponded with the motion at the truncation point of a full-length SCR under vessel motion. Out-of-plane vortex-induced vibration (VIV) was confirmed under pure top vessel motions, characterized with distinctive time-varying features. Results further indicate that vessel motion-induced VIV was strongly dependent on the KC number and the instantaneous equivalent flow profile. Meanwhile, tension variation was found to be another key factor causing response discrepancy between the ‘lift-up’ and ‘push-down’ phase for the large top vessel motion case. Finally, the relationship between the out-of-plane VIV dominant response frequency, maximum equivalent flow velocity and KC number were unveiled, which provides references for future vessel motion-induced VIV predictions.
Shixiao Fu - One of the best experts on this subject based on the ideXlab platform.
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evaluation of vortex induced vibration of a steel catenary riser in steady current and vessel motion induced oscillatory current
Journal of Fluids and Structures, 2018Co-Authors: Shixiao Fu, Jungao Wang, Rolf BaarholmAbstract:Abstract A large-Scale Model Test of a truncated steel catenary riser (SCR) was performed in an ocean basin to investigate the riser responses under pure steady uniform current and pure vessel motions separately. Out-of-plane vortex-induced vibration (VIV) was confirmed to have occurred under both Test conditions. A comparative analysis and discussion were carried out on selected cases in terms of out-of-plane VIV responses, VIV developing mechanisms and the fatigue damage contribution. Results indicate that both steady current-induced and vessel motion-induced VIV responses are dominated by strong travelling waves, but vessel motion-induced VIV responses are more ‘intermittent’ with respect to the response amplitude and frequency owing to its space- and time-varying shedding frequency. ‘Power-in’ regions are further estimated to understand the VIV developing mechanisms for both Test conditions. Finally, fatigue damages are evaluated showing the damage by vessel motion-induced VIV is comparable and at the same level as uniform current-induced VIV, which highlights the great importance of vessel motion-induced VIV, which cannot be neglected in the design and analysis for SCR systems.
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distribution of drag force coefficient along a flexible riser undergoing viv in sheared flow
Ocean Engineering, 2016Co-Authors: Leijian Song, Shixiao Fu, Mengmeng Zhang, Yifan ChenAbstract:Abstract The drag force coefficients of a flexible riser undergoing vortex-induced vibration (VIV) in sheared flow are investigated for Reynolds numbers (Re) up to 1.2×105. Based on the drag forces theoretically calculated by the beam theory using the strains measured in a Scale Model Test, the properties and distribution of the drag coefficients are investigated, and a new empirical Model for estimating the drag coefficient on a flexible riser undergoing VIV is proposed. The results show that VIV leads to non-uniform distribution of the drag coefficient and amplifies the drag coefficient, and the local drag coefficient can reach up to 3.2. For Re values from 1.0×104–1.2×105, the mean drag coefficient is between 1.3 and 2.0 and decreases as Re increases. Furthermore, the empirical drag coefficient prediction Model obtained from experiments under low Re is not suitable for high Re. The corrected empirical prediction Model, which accounts for the effect of the flow velocity, the VIV dominant mode number and the dominant frequency, can be used to predict riser drag coefficients under VIV more accurately at high Re values up to 1.2×105.
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out of plane vortex induced vibration of a steel catenary riser caused by vessel motions
Ocean Engineering, 2015Co-Authors: Jungao Wang, Shixiao Fu, Rolf Baarholm, Jie Wu, Carl M LarsenAbstract:A large-Scale Model Test of a truncated steel catenary riser (SCR) was performed in an ocean basin to investigate the riser responses under top vessel motion. Top end of the Model was forced to oscillate at given motion trajectories, corresponded with the motion at the truncation point of a full-length SCR under vessel motion. Out-of-plane vortex-induced vibration (VIV) was confirmed under pure top vessel motions, characterized with distinctive time-varying features. Results further indicate that vessel motion-induced VIV was strongly dependent on the KC number and the instantaneous equivalent flow profile. Meanwhile, tension variation was found to be another key factor causing response discrepancy between the ‘lift-up’ and ‘push-down’ phase for the large top vessel motion case. Finally, the relationship between the out-of-plane VIV dominant response frequency, maximum equivalent flow velocity and KC number were unveiled, which provides references for future vessel motion-induced VIV predictions.
Reiko Kuwano - One of the best experts on this subject based on the ideXlab platform.
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influence of location of subsurface structures on development of underground cavities induced by internal erosion
Soils and Foundations, 2015Co-Authors: Mari Sato, Reiko KuwanoAbstract:Abstract This paper revealed the influence of buried structures on the development of underground cavities with internal erosion from the breakage of sewer pipes, and investigated the spatial distribution of a loose ground where the strength was decreased due to this erosion. Moreover, the collapse of the underground cavities induced sinkhole accidents. A series of laboratory Model Tests was conducted to examine the relevance of the locations of subsurface structures and the expansion of underground cavities. Following the Model Tests, the strength of the Model ground was examined by means of a series of laboratory penetration Tests. The results of these laboratory Tests showed that the subsurface structures brought about a variation in the formation of cavities as a result of a variation in the pathway of localized seepage that had developed throughout the nearest path from the surface to the cracks in the pipes. In addition, this paper found that developments in the loose ground were induced without the accompaniment of visible deformation. A large-Scale Model Test indicated the applicability of the results of the laboratory Model Tests to the practical Scale of the ground. Overall, we proposed the necessity of considering the mutual effect of subsurface structures on the progression of cavity expansion due to internal erosion.
Teruo Ooshima - One of the best experts on this subject based on the ideXlab platform.
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Research and Development of a Self-Walking Vertical Mining System Using DTH Drilling Unit and the Scale Model Test
Volume 6: Ocean Space Utilization, 2019Co-Authors: Yoshiyasu Watanabe, Keisuke Watanabe, Hideyuki Suzuki, Teruo Ooshima, Yoshiaki TsukamotoAbstract:Abstract Traditional subsea mining systems use a heavy subsea crawler, which has a big drill and scrapes the mineral deposit horizontally and have limitations of seafloor inclination, roughness and softness. Those traditional systems also have issues from operational and economical points of view. Furthermore, traditional on-board drilling machines and seabed drilling machines are used for core sampling by drilling to analyze mineral contents of seafloor deposits at the stage of mineral resource estimation before the production but operational and economical efficiencies are required to those traditional systems as well. The objective of this research is to develop an innovative Self-Walking Vertical Mining System (SW-VMS) that overcomes these issues. The system is a fully submerged eight-legged jack up platform and is able to walk autonomously on a rough, soft and inclined seafloor. The SW-VMS can be used both as the mining system to mine seafloor deposits and as the sample drilling system to analyze mineral contents in-situ and on-land efficiently before the mining with a DTH drilling unit. This paper introduces the detail of the SW-VMS as the mining system at first and then introduces the concept of the SW-VMS as the sample drilling system and finally the results of the Scale Model Test of the SW-VMS on-land are shown. The Scale Model Test has been carried out to confirm the walking ability of the SW-VMS from the structural and autonomous control points of view. The Scale of the Test Model is approximately 1/40 of the preliminary design of the SW-VMS which has been already completed. The Test consists of Test cases of walking on a flat foundation, on a flat foundation including partially soft foundations and on inclined foundations of up to 45 degrees.
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Scale Model Test of a Self-Walking Vertical Mining System Using DTH for Seafloor Mining and Sampling
2018 OCEANS - MTS IEEE Kobe Techno-Oceans (OTO), 2018Co-Authors: Yoshiyasu Watanabe, Keisuke Watanabe, Hideyuki Suzuki, Fumio Yuasa, Teruo OoshimaAbstract:Traditional subsea mining systems use a heavy subsea crawler, which has a big drill and scrapes the mineral deposit horizontally and have limitations of seafloor inclination, roughness and softness. Also the traditional systems have issues from operational and economical points of view. Furthermore, operational and economical efficiencies are required for sampling and analyzing of mineral deposits at the stage of mineral resource estimation before the production. The objective of this research is to develop an innovative Self-Walking Vertical Mining System (SW-VMS) that overcomes these issues. The system is a fully submerged eight-legged jack up platform and is able to walk by itself on a rough, soft and inclined seafloor. It mines seafloor, obtains samples and analyzes in-situ efficiently. In the paper before previous one[1], Vertical Mining System (VMS) was introduced. It was a four-legged jack up platform where a DTH drill unit and a moving beam were mounted. Though the system had many advantages, it had a disadvantage in relocation, because an installation and relocation vessel (IRV) is required during the operation. The previous paper[2] introduced a concept and preliminary design of a Self-Walking Vertical Mining system (SW-VMS) that eliminates the use of the IRV and reduces the project cost and period. This paper introduces a concept of sampling and in-situ analysis system and results of on-land Scale Model Test of SW-VMS.
