The DFI-1 submarine pipeline was investigated using a dual-frequency side-scan sonar and a swath sounder system. More than a hundred scour pits under the pipeline were found, most of which have caused the span of the ...The DFI-1 submarine pipeline was investigated using a dual-frequency side-scan sonar and a swath sounder system. More than a hundred scour pits under the pipeline were found, most of which have caused the span of the pipeline to increase and threatened its safety. The maximum allowable free span length （MAFSL） of the pipeline was determined through the limitations re- garding maximum allowable stress under static or quasi-static loads and the onset of Vortex Induced Vibrations （VIV） under different hydrodynamic actions. The results show that the MAFSL under static conditions is 56m. However, the MAFSLs are 30m and 20m under ordinary weather conditions and hurricane-induced currents for the 100-year return period, respectively, to avoid VIV as cal- culated by using the highest safety class factor. It is suggested that spanning pipelines longer than 20 m should be supported. Addi- tionally, eight successive spans which may also threaten the pipeline were proposed. The most hazardous scour pits are along the pipeline section from KP42 to KP51.展开更多
Owing to the complex environmental conditions, suspension could induce complicated forces on submarine pipelines and even cause vortex-induced vibration, resulting in fatigue damage of pipelines. Through aiming at the...Owing to the complex environmental conditions, suspension could induce complicated forces on submarine pipelines and even cause vortex-induced vibration, resulting in fatigue damage of pipelines. Through aiming at the 28-inch submarine pipeline in the East China Sea, the pipeline was segmented according to the similarity, considering the factors of pipe assembly, typhoon, current, wave and seabed topography. The effects of span length on natural frequency in each section of submarine pipeline were analyzed by finite element model. The maximum safe span length allowed by each pipeline section was verified by fatigue cumulative damage theory, and the fatigue life of each pipeline section were predicted. The results showed that each order natural frequency of the pipeline decreased with the increase of span length. The calculated results of empirical formulas were much smaller than those of the FEM analysis. The increase of the gap between the suspended pipeline and the seabed was beneficial to enhance the fatigue life of the suspended pipeline.展开更多
We present an incorporation of the kinetic Monte Carlo(kMC)simulation with the adjacency matrix(AM)method to investigate structural parameters of randomly branched polymers.The AMs of branched polymers are obtained by...We present an incorporation of the kinetic Monte Carlo(kMC)simulation with the adjacency matrix(AM)method to investigate structural parameters of randomly branched polymers.The AMs of branched polymers are obtained by the growth generation model,which is employed in the kMC simulation based on Gillespie’s algorithm.Of particular interest is the effect of the branched units on the relevant structural parameters.As an application in randomly hyperbranched polymers formed by AB_(2)type of monomers,average maximum span length,average length of sub-chains,number distribution of branched units,and meansquare radius of gyration are calculated.It is shown that the branched units can give rise to a significant effect on these physical quantities,whereby such a structure-property relationship can be employed to optimize reaction conditions and implement material designs.展开更多
基金supported by the National Basic Research Program of China (973 Program) (Grant No.2005CB422304)the Ocean University of China Scientific Research Start-up Funds Project for Introduced Talents
文摘The DFI-1 submarine pipeline was investigated using a dual-frequency side-scan sonar and a swath sounder system. More than a hundred scour pits under the pipeline were found, most of which have caused the span of the pipeline to increase and threatened its safety. The maximum allowable free span length （MAFSL） of the pipeline was determined through the limitations re- garding maximum allowable stress under static or quasi-static loads and the onset of Vortex Induced Vibrations （VIV） under different hydrodynamic actions. The results show that the MAFSL under static conditions is 56m. However, the MAFSLs are 30m and 20m under ordinary weather conditions and hurricane-induced currents for the 100-year return period, respectively, to avoid VIV as cal- culated by using the highest safety class factor. It is suggested that spanning pipelines longer than 20 m should be supported. Addi- tionally, eight successive spans which may also threaten the pipeline were proposed. The most hazardous scour pits are along the pipeline section from KP42 to KP51.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.11802168 and 51575331)project funded by China Postdoctoral Science Foundation(No.2019M661458)
文摘Owing to the complex environmental conditions, suspension could induce complicated forces on submarine pipelines and even cause vortex-induced vibration, resulting in fatigue damage of pipelines. Through aiming at the 28-inch submarine pipeline in the East China Sea, the pipeline was segmented according to the similarity, considering the factors of pipe assembly, typhoon, current, wave and seabed topography. The effects of span length on natural frequency in each section of submarine pipeline were analyzed by finite element model. The maximum safe span length allowed by each pipeline section was verified by fatigue cumulative damage theory, and the fatigue life of each pipeline section were predicted. The results showed that each order natural frequency of the pipeline decreased with the increase of span length. The calculated results of empirical formulas were much smaller than those of the FEM analysis. The increase of the gap between the suspended pipeline and the seabed was beneficial to enhance the fatigue life of the suspended pipeline.
基金supported by the Central Guidance on Local Science and Technology Development Fund of Hebei Province (No.236Z7601G)the Interdisciplinary Research Program of Natural Science of Hebei University, China (No.DXK202112)。
文摘We present an incorporation of the kinetic Monte Carlo(kMC)simulation with the adjacency matrix(AM)method to investigate structural parameters of randomly branched polymers.The AMs of branched polymers are obtained by the growth generation model,which is employed in the kMC simulation based on Gillespie’s algorithm.Of particular interest is the effect of the branched units on the relevant structural parameters.As an application in randomly hyperbranched polymers formed by AB_(2)type of monomers,average maximum span length,average length of sub-chains,number distribution of branched units,and meansquare radius of gyration are calculated.It is shown that the branched units can give rise to a significant effect on these physical quantities,whereby such a structure-property relationship can be employed to optimize reaction conditions and implement material designs.
