The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of ...The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of the riser under VIVs are calculated and the mean stresses,the number of stress cycles and amplitudes are determined by the rainflow counting method.The Palmgren-Miner rule for cumulative damage theory with a specified S-N curve is used to estimate the fatigue life of the riser.The corresponding numerical programs numerical simulation of vortex-induced vibrations (NSVIV) which can be used to calculate the VIV response and fatigue life of the riser are compiled.Finally the influences of the riser's parameters such as flexural rigidity,top tension and internal flow velocity on the fatigue life of the riser are analyzed in detail and some conclusions are drawn.展开更多
The bending stresses of top tensioned riser(TTR) under combined excitations of currents,random waves and vessel motions are presented in this paper,and the effect of the internal flowing fluid on the riser stresses is...The bending stresses of top tensioned riser(TTR) under combined excitations of currents,random waves and vessel motions are presented in this paper,and the effect of the internal flowing fluid on the riser stresses is also considered.The computation programs which are used to solve the differential equations in the time domain are compiled and the principal factors of concern including the angular movements at the upper and lower ends of the riser,lateral displacements and bending stresses are presented.Then the effects of current velocity,random wave,top tension,vessel mean offset,low frequency motion and internal flow velocity on the bending stresses of the riser are analyzed in detail.展开更多
The casing damage has been a big problem in oilfield production. The current detection methods mostly are used after casing damage, which is not very effective. With the rapid development of China's offshore oil i...The casing damage has been a big problem in oilfield production. The current detection methods mostly are used after casing damage, which is not very effective. With the rapid development of China's offshore oil industry, the number of offshore oil wells is becoming larger and larger. Because the cost of offshore oil well is very high, the casing damage will cause huge economic losses. What's more, it can also bring serious pollution to marine environment. So the effective methods of detecting casing damage are required badly. The accumulation of stress is the main reason for the casing damage. Magnetic anisotropy technique based on counter magnetostriction effect can detect the stress of casing in real time and help us to find out the hidden dangers in time. It is essential for us to prevent the casing damage from occurring. However, such technique is still in the development stage. Previous studies mostly got the relationship between stress and magnetic signals by physical experiment, and the study of physical mechanism in relative magnetic permeability connecting the stress and magnetic signals is rarely reported. The present paper uses the ANSYS to do the three-dimensional finite element numerical simulation to study how the relative magnetic permeability works for the oil casing model. We find that the quantitative relationship between the stress' s variation and magnetic induction intensity's variation is: Δδ =K* ΔB, K = 8.04×109, which is proved correct by physical experiment.展开更多
基金supported by the High Technology Research and Development Program of China (863 Program,Grant Nos.2006AA09Z356 and 2007AA09Z313)
文摘The fatigue life of top tensioned risers under vortex-induced vibrations (VIVs) with consideration of the effect of internal flowing fluid on the riser is analyzed in the time domain.The long-term stress histories of the riser under VIVs are calculated and the mean stresses,the number of stress cycles and amplitudes are determined by the rainflow counting method.The Palmgren-Miner rule for cumulative damage theory with a specified S-N curve is used to estimate the fatigue life of the riser.The corresponding numerical programs numerical simulation of vortex-induced vibrations (NSVIV) which can be used to calculate the VIV response and fatigue life of the riser are compiled.Finally the influences of the riser's parameters such as flexural rigidity,top tension and internal flow velocity on the fatigue life of the riser are analyzed in detail and some conclusions are drawn.
基金supported by the High Technology Research and Development Program of China (863 Program, Grant Nos SQ2009AA09Z3487852 and 2007AA09Z313)
文摘The bending stresses of top tensioned riser(TTR) under combined excitations of currents,random waves and vessel motions are presented in this paper,and the effect of the internal flowing fluid on the riser stresses is also considered.The computation programs which are used to solve the differential equations in the time domain are compiled and the principal factors of concern including the angular movements at the upper and lower ends of the riser,lateral displacements and bending stresses are presented.Then the effects of current velocity,random wave,top tension,vessel mean offset,low frequency motion and internal flow velocity on the bending stresses of the riser are analyzed in detail.
基金supported by the National Natural Science Foundation of China(No.41174157)
文摘The casing damage has been a big problem in oilfield production. The current detection methods mostly are used after casing damage, which is not very effective. With the rapid development of China's offshore oil industry, the number of offshore oil wells is becoming larger and larger. Because the cost of offshore oil well is very high, the casing damage will cause huge economic losses. What's more, it can also bring serious pollution to marine environment. So the effective methods of detecting casing damage are required badly. The accumulation of stress is the main reason for the casing damage. Magnetic anisotropy technique based on counter magnetostriction effect can detect the stress of casing in real time and help us to find out the hidden dangers in time. It is essential for us to prevent the casing damage from occurring. However, such technique is still in the development stage. Previous studies mostly got the relationship between stress and magnetic signals by physical experiment, and the study of physical mechanism in relative magnetic permeability connecting the stress and magnetic signals is rarely reported. The present paper uses the ANSYS to do the three-dimensional finite element numerical simulation to study how the relative magnetic permeability works for the oil casing model. We find that the quantitative relationship between the stress' s variation and magnetic induction intensity's variation is: Δδ =K* ΔB, K = 8.04×109, which is proved correct by physical experiment.
文摘运用HE染色法观察小鼠肝脏在添加酪氨酸和半胱氨酸后是否有损伤;油红O染色法观察小鼠肝脏脂质沉积的变化;血清生化检测小鼠血脂四项的表达水平;最后用RT-qPCR和Western blot法检测小鼠肝脏中产热相关基因的表达水平。结果显示,添加酪氨酸和半胱氨酸后小鼠体质量下降,肝脏并未出现明显损伤并且小鼠肝脏中的脂滴含量下降;除Ⅱ组的低密度脂蛋白胆固醇(low density lipoprotein cholesterol,LDL-C)无显著下降外,添加了酪氨酸和半胱氨酸的小鼠血液中的甘油三酯(triglyceride,TG)、总胆固醇(total cholesterol,TC)和LDL-C都显著降低;高密度脂蛋白胆固醇(high density lipoprotein cholesterol,HDL-C)只有Ⅵ组显著升高。RT-qPCR结果显示,常温条件下除Ⅱ组的PPAR-α的mRNA无显著表达外,其他产热相关mRNA显著升高;冷暴露条件下只有Ⅴ组的PPAR-α的mRNA上升显著,除Ⅵ组UCP1的mRNA上升显著,其他3个产热相关mRNA极显著上升。Western blot结果显示,常温条件下Ⅱ组的产热相关蛋白显著上升,其中PGC-1α上升极显著,Ⅲ组除UCP1上升显著外,其他产热蛋白无显著上升;冷暴露条件下Ⅴ组的PPAR-α升高显著,其他产热蛋白上升不显著,Ⅵ组的产热相关蛋白都有显著上升,其中PPAR-α和PPAR-γ上升极显著。结果表明,联合使用酪氨酸和半胱氨酸可以降低小鼠体质量并改善小鼠的血脂水平,提高小鼠肝脏的产热能力。
