Under unanticipated natural disasters, any failure of structure components may cause the crash of an entire structure system. Resilience is an important metric for the structure system. Although many resilience metric...Under unanticipated natural disasters, any failure of structure components may cause the crash of an entire structure system. Resilience is an important metric for the structure system. Although many resilience metrics and assessment approaches are proposed for engineering system, they are not suitable for complex structure systems, since the failure mechanisms of them are different under the influences of natural disasters. This paper proposes a novel resilience assessment metric for structure system from a macroscopic perspective, named structure resilience, and develops a corresponding assessment approach based on remaining useful life of key components. Dynamic Bayesian networks(DBNs) and Markov are applied to establish the resilience assessment model. In the degradation process, natural degradation and accelerated degradation are modelled by using Bayesian networks, and then coupled by using DBNs. In the recovery process, the model is established by combining Markov and DBNs. Subsea oil and gas pipelines are adopted to demonstrate the application of the proposed structure metric and assessment approach.展开更多
Vortex induced vibration(VIV)is a challenge in ocean engineering.Several devices including fairings have been designed to suppress VIV.However,how to optimize the design of suppression devices is still a problem to be...Vortex induced vibration(VIV)is a challenge in ocean engineering.Several devices including fairings have been designed to suppress VIV.However,how to optimize the design of suppression devices is still a problem to be solved.In this paper,an optimization design methodology is presented based on data-driven models and genetic algorithm(GA).Data-driven models are introduced to substitute complex physics-based equations.GA is used to rapidly search for the optimal suppression device from all possible solutions.Taking fairings as example,VIV response database for different fairings is established based on parameterized models in which model sections of fairings are controlled by several control points and Bezier curves.Then a data-driven model,which can predict the VIV response of fairings with different sections accurately and efficiently,is trained through BP neural network.Finally,a comprehensive optimization method and process is proposed based on GA and the data-driven model.The proposed method is demonstrated by its application to a case.It turns out that the proposed method can perform the optimization design of fairings effectively.VIV can be reduced obviously through the optimization design.展开更多
Leakage is one of the most important reasons for failure of hydraulic systems.The accurate positioning of leakage is of great significance to ensure the safe and reliable operation of hydraulic systems.For early stage...Leakage is one of the most important reasons for failure of hydraulic systems.The accurate positioning of leakage is of great significance to ensure the safe and reliable operation of hydraulic systems.For early stage of leakage,the pressure of the hydraulic circuit does not change obviously and therefore cannot be monitored by pressure sensors.Meanwhile,the pressure of the hydraulic circuit changes frequently due to the influence of load and state of the switch,which further reduces the accuracy of leakage localization.In the work,a novel Bayesian networks(BNs)-based data-driven early leakage localization approach for multi-valve systems is proposed.Wavelet transform is used for signal noise reduction and BNs-based leak localization model is used to identify the location of leakage.A normalization model is developed to improve the robustness of the leakage localization model.A hydraulic system with eight valves is used to demonstrate the application of the proposed early micro-leakage detection and localization approach.展开更多
The safety of risers in hang-off states is a vital challenge in offshore oil and gas engineering.A new hang-off system installed on top of risers is proposed for improving the security of risers.This approach leads to...The safety of risers in hang-off states is a vital challenge in offshore oil and gas engineering.A new hang-off system installed on top of risers is proposed for improving the security of risers.This approach leads to a challenging problem:coupling the dynamics of risers with a new hang-off system combined with multiple structures and complex constraints.To accurately analyze the dynamic responses of the coupled system,a coupled dynamic model is established based on the Euler-Bernoulli beam-column theory and penalty function method.A comprehensive analysis method is proposed for coupled dynamic analysis by combining the finite element method and the Newmarkβmethod.An analysis program is also developed in MATLAB for dynamic simulation.The simulation results show that the dynamic performances of the risers at the top part are significantly improved by the new hang-off system,especially the novel design,which includes the centralizer and articulation joint.The bending moment and lateral deformation of the risers at the top part decrease,while the hang-off joint experiences a great bending moment at the bottom of the lateral restraint area which requires particular attention in design and application.The platform navigation speed range under the safety limits of risers expands with the new hang-off system in use.展开更多
A multibody system including a drilling riser system,tensioners and a floating platform is key equipment for offshore oil and gas drilling.Most of the previous studies only focus on the drilling riser system rather th...A multibody system including a drilling riser system,tensioners and a floating platform is key equipment for offshore oil and gas drilling.Most of the previous studies only focus on the drilling riser system rather than the multibody system.Mechanical characteristics of the deepwater drilling riser system cannot be analyzed accurately in a simplified model.Therefore,a three-dimensional multibody analysis program is developed.The static and dynamic characteristics of the deepwater drilling riser system under different platform motions are analyzed based on the developed program.The results show that the static displacement of the riser system with tensioners is smaller than that without tensioners,which means the tensioners can suppress the deformation of the riser system.Under surge and sway motions of the platform,the dynamic displacement of the riser system with tensioners is also smaller than that without tensioners due to the tensioner suppression effect.Besides,the heave motion induces a uniform axial vibration of the riser system,while roll and pitch motions excite the riser system to vibrate laterally.Compared with the stress amplitude due to surge and sway motions,the stress amplitude of the riser system due to heave,roll and pitch motions is relatively small but cannot be neglected.展开更多
The disc-seal single screw pump(DSSP)used in the field of high viscosity oily sludge transport has a huge advantage.However,there is no research on the pressurization characteristics of the DSSP at present,which makes...The disc-seal single screw pump(DSSP)used in the field of high viscosity oily sludge transport has a huge advantage.However,there is no research on the pressurization characteristics of the DSSP at present,which makes its application limited.In view of this,the pressurization process mathematical model of the DSSP was established based on the geometric model of the pump.By using this model,the pressurization characteristics of DSSP and the influence of working parameters on the pressurization process were studied combined with the principle of back-flow pressurization.Analysis results show that the instantaneous pressurization process could be realized mainly depending on the reflux pressurization from the outlet chamber to the pressurization chamber when the screw rotor rotating angle is located at-5°to+5°.The pressure in the pressurization chamber will increase with the increase of working parameters which include inlet pressure,outlet pressure,screw rotation velocity and dynamic viscosity of fluid medium in the area of flow-back pressurization.The screw rotation velocity and the viscosity of the conveying medium have significant effects on the peak pressure in the pressurization chamber,and the peak pressure in the pressurization chamber is proportional to the screw rotation velocity and the dynamic viscosity coefficient of the conveying medium.The proportional coefficient between the peak pressure and the screw rotation velocity is 6.29×10~4.The proportional coefficient between the peak pressure and the dynamic viscosity of the conveying medium is 6.28×10~6.展开更多
Recently,there are hesitations in the application scope of the classical Cassie theory and Wenzel theory.In this paper,Molecular Dynamics(MD)simulations are used to study these two theories used in the nanoscale and f...Recently,there are hesitations in the application scope of the classical Cassie theory and Wenzel theory.In this paper,Molecular Dynamics(MD)simulations are used to study these two theories used in the nanoscale and find their limitations.The effect of parameters including solid fractions(or roughness factors),arrangement of pillars(with same solid fractions),pillar height,and droplet size on contact angles was investigated.It shows that the Cassie equation is suitable for droplets on uniform pillared surfaces including different solid fractions,arrangement of pillars and pillar height,when there is no meniscus of droplets.The Wenzel equation is also suitable for droplets on uniform pillared surfaces including different roughness factors,arrangement of pillars and pillar heights.Moreover,whether the droplet size has an influence on the contact angle depends on the pinned place of the contact line.In the Wenzel state,the contact line is pinned although increasing the droplet size,resulting in increasing the contact angle,while the contact angle decreases to the initial value again when the droplet size increases enough to allow the contact line moving to the next pillar.The results provide insights toward the wettability of droplets on surfaces in nanoscale.展开更多
Superhydrophobic surfaces(SHS)and slippery lubricant-infused porous surfaces(SLIPS)attract great attention due to their multiple properties in both industries and our daily lives.Here,we first fabricated the SHS with ...Superhydrophobic surfaces(SHS)and slippery lubricant-infused porous surfaces(SLIPS)attract great attention due to their multiple properties in both industries and our daily lives.Here,we first fabricated the SHS with micro-scale flower-like structures composed of nano-sheets on pipeline steel substrate.Then,we obtained the SLIPS by spin-coating lubricant into gaps of micro-scale flower-like structures,with the air still trapped among gaps of nano-sheets.The SLIPS shows excellent liquid repellency as the SHS.The SLIPS also shows stability after the scour of flowing water.These results of polarization curves(Tafel)and electrochemical impedance spectroscopies deduced the SLIPS with better and more stable anti-corrosion property than the SHS.Compared with the SHS,the lack of attachment and CaCO_(3) on the SLIPS indicates that the SLIPS demonstrates better anti-fouling and anti-scaling properties than the SHS.Moreover,the SLIPS shows promising wear resistance under the abrasion simulated by sandpaper compared with the SHS.Notably,the air trapped among nano-sheets is conducive to the lubricant flowing to the surface quickly,exhibiting spontaneous self-healing in atmosphere,even if part flower-like structures of the SLIPS subject to damage with the lubricant consumed after scratched.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No. 51779267)the Taishan Scholars Project (Grant No. tsqn201909063)+3 种基金the Science and Technology Support Plan for Youth Innovation of Universities in Shandong Province (Grant No.2019KJB016)the National Key Research and Development Program of China (Grant No. 2019YFE0105100)the Fundamental Research Funds for the Central Universitiesthe Opening Fund of National Engineering Laboratory of Offshore Geophysical and Exploration Equipment (Grant No.20CX02301A)。
文摘Under unanticipated natural disasters, any failure of structure components may cause the crash of an entire structure system. Resilience is an important metric for the structure system. Although many resilience metrics and assessment approaches are proposed for engineering system, they are not suitable for complex structure systems, since the failure mechanisms of them are different under the influences of natural disasters. This paper proposes a novel resilience assessment metric for structure system from a macroscopic perspective, named structure resilience, and develops a corresponding assessment approach based on remaining useful life of key components. Dynamic Bayesian networks(DBNs) and Markov are applied to establish the resilience assessment model. In the degradation process, natural degradation and accelerated degradation are modelled by using Bayesian networks, and then coupled by using DBNs. In the recovery process, the model is established by combining Markov and DBNs. Subsea oil and gas pipelines are adopted to demonstrate the application of the proposed structure metric and assessment approach.
基金supported by the National Natural Science Foundation of China(Grant No.51809279)the Major National Science and Technology Program(Grant No.2016ZX05028-001-05)+1 种基金Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT14R58)the Fundamental Research Funds for the Central Universities,that is,the Opening Fund of National Engineering Laboratory of Offshore Geophysical and Exploration Equipment(Grant No.20CX02302A).
文摘Vortex induced vibration(VIV)is a challenge in ocean engineering.Several devices including fairings have been designed to suppress VIV.However,how to optimize the design of suppression devices is still a problem to be solved.In this paper,an optimization design methodology is presented based on data-driven models and genetic algorithm(GA).Data-driven models are introduced to substitute complex physics-based equations.GA is used to rapidly search for the optimal suppression device from all possible solutions.Taking fairings as example,VIV response database for different fairings is established based on parameterized models in which model sections of fairings are controlled by several control points and Bezier curves.Then a data-driven model,which can predict the VIV response of fairings with different sections accurately and efficiently,is trained through BP neural network.Finally,a comprehensive optimization method and process is proposed based on GA and the data-driven model.The proposed method is demonstrated by its application to a case.It turns out that the proposed method can perform the optimization design of fairings effectively.VIV can be reduced obviously through the optimization design.
基金Project(51779267)supported by the National Natural Science Foundation of ChinaProject(2019YFE0105100)supported by the National Key Research and Development Program of China+2 种基金Project(tsqn201909063)supported by the Taishan Scholars Project,ChinaProject(20CX02301A)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2019KJB016)supported by the Science and Technology Support Plan for Youth Innovation of Universities in Shandong Province,China。
文摘Leakage is one of the most important reasons for failure of hydraulic systems.The accurate positioning of leakage is of great significance to ensure the safe and reliable operation of hydraulic systems.For early stage of leakage,the pressure of the hydraulic circuit does not change obviously and therefore cannot be monitored by pressure sensors.Meanwhile,the pressure of the hydraulic circuit changes frequently due to the influence of load and state of the switch,which further reduces the accuracy of leakage localization.In the work,a novel Bayesian networks(BNs)-based data-driven early leakage localization approach for multi-valve systems is proposed.Wavelet transform is used for signal noise reduction and BNs-based leak localization model is used to identify the location of leakage.A normalization model is developed to improve the robustness of the leakage localization model.A hydraulic system with eight valves is used to demonstrate the application of the proposed early micro-leakage detection and localization approach.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52271300,52071337,and 51809279)the National Key Research and Development Program of China(Grant No.2022YFC2806501)the High-tech Ship Research Projects Sponsored by MIIT(Grant No.CBG2N21-4-2-5).
文摘The safety of risers in hang-off states is a vital challenge in offshore oil and gas engineering.A new hang-off system installed on top of risers is proposed for improving the security of risers.This approach leads to a challenging problem:coupling the dynamics of risers with a new hang-off system combined with multiple structures and complex constraints.To accurately analyze the dynamic responses of the coupled system,a coupled dynamic model is established based on the Euler-Bernoulli beam-column theory and penalty function method.A comprehensive analysis method is proposed for coupled dynamic analysis by combining the finite element method and the Newmarkβmethod.An analysis program is also developed in MATLAB for dynamic simulation.The simulation results show that the dynamic performances of the risers at the top part are significantly improved by the new hang-off system,especially the novel design,which includes the centralizer and articulation joint.The bending moment and lateral deformation of the risers at the top part decrease,while the hang-off joint experiences a great bending moment at the bottom of the lateral restraint area which requires particular attention in design and application.The platform navigation speed range under the safety limits of risers expands with the new hang-off system in use.
基金This work was financially supported by National Natural Science Foundation of China(Grant No.51809279)Major National Science and Technology Program(Grant No.2016ZX05028-001-05)+3 种基金National Key R&D Program of China(Grant No.2017YFC0804500)Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT14R58)the Fundamental Research Funds for the Central Universities(Grant No.20CX02302A)the Opening Fund of National Engineering Laboratory of Offshore Geophysical and Exploration Equipment(Grant No.20CX02302A)。
文摘A multibody system including a drilling riser system,tensioners and a floating platform is key equipment for offshore oil and gas drilling.Most of the previous studies only focus on the drilling riser system rather than the multibody system.Mechanical characteristics of the deepwater drilling riser system cannot be analyzed accurately in a simplified model.Therefore,a three-dimensional multibody analysis program is developed.The static and dynamic characteristics of the deepwater drilling riser system under different platform motions are analyzed based on the developed program.The results show that the static displacement of the riser system with tensioners is smaller than that without tensioners,which means the tensioners can suppress the deformation of the riser system.Under surge and sway motions of the platform,the dynamic displacement of the riser system with tensioners is also smaller than that without tensioners due to the tensioner suppression effect.Besides,the heave motion induces a uniform axial vibration of the riser system,while roll and pitch motions excite the riser system to vibrate laterally.Compared with the stress amplitude due to surge and sway motions,the stress amplitude of the riser system due to heave,roll and pitch motions is relatively small but cannot be neglected.
基金supported by National Key R&D Program of China[NO.2020YFB2010002]National Natural Science Foundation of China[NO.51706247,NO.51975585]the Fundamental Research Funds for the Central Universities and the Opening Fund of National Engineering Laboratory of Offshore Geophysical and Exploration Equipment[NO.20CX02312A]
文摘The disc-seal single screw pump(DSSP)used in the field of high viscosity oily sludge transport has a huge advantage.However,there is no research on the pressurization characteristics of the DSSP at present,which makes its application limited.In view of this,the pressurization process mathematical model of the DSSP was established based on the geometric model of the pump.By using this model,the pressurization characteristics of DSSP and the influence of working parameters on the pressurization process were studied combined with the principle of back-flow pressurization.Analysis results show that the instantaneous pressurization process could be realized mainly depending on the reflux pressurization from the outlet chamber to the pressurization chamber when the screw rotor rotating angle is located at-5°to+5°.The pressure in the pressurization chamber will increase with the increase of working parameters which include inlet pressure,outlet pressure,screw rotation velocity and dynamic viscosity of fluid medium in the area of flow-back pressurization.The screw rotation velocity and the viscosity of the conveying medium have significant effects on the peak pressure in the pressurization chamber,and the peak pressure in the pressurization chamber is proportional to the screw rotation velocity and the dynamic viscosity coefficient of the conveying medium.The proportional coefficient between the peak pressure and the screw rotation velocity is 6.29×10~4.The proportional coefficient between the peak pressure and the dynamic viscosity of the conveying medium is 6.28×10~6.
基金This work was supported by the National Natural Science Foundation of China(51905315)Shandong Provincial Natural Science Foundation(ZR2019BEMO12)+3 种基金the Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents(2019RCJJ001)the Fundamental Research Funds for theCentral Universities(20CX02317A)the Opening Fund of National Engineering Laboratory of Offshore Gcophysical and Exploration Equipmentthe Project of Shandong Province Higher Educational Young Innovative Talent Introduction and Cultivation Team(Environment function material innovation team).
文摘Recently,there are hesitations in the application scope of the classical Cassie theory and Wenzel theory.In this paper,Molecular Dynamics(MD)simulations are used to study these two theories used in the nanoscale and find their limitations.The effect of parameters including solid fractions(or roughness factors),arrangement of pillars(with same solid fractions),pillar height,and droplet size on contact angles was investigated.It shows that the Cassie equation is suitable for droplets on uniform pillared surfaces including different solid fractions,arrangement of pillars and pillar height,when there is no meniscus of droplets.The Wenzel equation is also suitable for droplets on uniform pillared surfaces including different roughness factors,arrangement of pillars and pillar heights.Moreover,whether the droplet size has an influence on the contact angle depends on the pinned place of the contact line.In the Wenzel state,the contact line is pinned although increasing the droplet size,resulting in increasing the contact angle,while the contact angle decreases to the initial value again when the droplet size increases enough to allow the contact line moving to the next pillar.The results provide insights toward the wettability of droplets on surfaces in nanoscale.
基金Natural Science Foundation(ZR2019BEM012)National Natural Science Foundation of China(51905315)+1 种基金Fundamental Research Funds for the Central Universities(20CX02316A)Opening Fund of National Engineering Laboratory of Offshore Geophysical and Exploration Equipment.
文摘Superhydrophobic surfaces(SHS)and slippery lubricant-infused porous surfaces(SLIPS)attract great attention due to their multiple properties in both industries and our daily lives.Here,we first fabricated the SHS with micro-scale flower-like structures composed of nano-sheets on pipeline steel substrate.Then,we obtained the SLIPS by spin-coating lubricant into gaps of micro-scale flower-like structures,with the air still trapped among gaps of nano-sheets.The SLIPS shows excellent liquid repellency as the SHS.The SLIPS also shows stability after the scour of flowing water.These results of polarization curves(Tafel)and electrochemical impedance spectroscopies deduced the SLIPS with better and more stable anti-corrosion property than the SHS.Compared with the SHS,the lack of attachment and CaCO_(3) on the SLIPS indicates that the SLIPS demonstrates better anti-fouling and anti-scaling properties than the SHS.Moreover,the SLIPS shows promising wear resistance under the abrasion simulated by sandpaper compared with the SHS.Notably,the air trapped among nano-sheets is conducive to the lubricant flowing to the surface quickly,exhibiting spontaneous self-healing in atmosphere,even if part flower-like structures of the SLIPS subject to damage with the lubricant consumed after scratched.
