Because the applications of single-anchor leg mooring yoke systems(SYSs)are rarely studied in the offshore industry,the design of such systems features some uncertainties.This paper investigated the effect of eccentri...Because the applications of single-anchor leg mooring yoke systems(SYSs)are rarely studied in the offshore industry,the design of such systems features some uncertainties.This paper investigated the effect of eccentricity on the wear of the topside axial bearing of a SYS.The eccentricity of the topside was verified by on-site inspection,and the axial bearing wear was found to be far more serious than the original design.The contact status between the axial bearing and flange surface was studied on the basis of the actual topside load by using nonlinear finite element analysis.Wear tests of the topside bearing under uniform and eccentric loads were also performed to study the effect of eccentric loads on the wear rate.The key parameters obtained from numerical simulations and experimentation were used to calculate the wear depth via a simplified linear wear model based on the product of the pressure and sliding distance.Results showed that eccentric loads are the main factor responsible for the excessive wear of topside axial bearings.展开更多
This paper presents some insights on the state-of-the-art practice that has been utilized recently in the inplace structural strength and fatigue analysis for topsides on deepwater floating platforms such as tension l...This paper presents some insights on the state-of-the-art practice that has been utilized recently in the inplace structural strength and fatigue analysis for topsides on deepwater floating platforms such as tension leg plat-form (TLP) and semi-submersibles. Emphases are put on analysis software,geometric and mass modeling,hydro-dynamic loading and its mapping,and analysis procedures. In addition,for the in-place analysis using structure analysis computer system (SACS),the procedure of Visual Basic for Application (VBA) is developed to map AQWA-LINE hydrodynamic loading to the SACS integrated hull/topsides model;for the in-place analysis using structure engineering system analysis model (SESAM),many computer aided applications are made to aid the post-processing. These applications have been used in structural analyses for a few TLP and semi-submersible plat-form topsides,and are briefly introduced in this paper.展开更多
When using topside choking to eliminate severe slugging in offshore pipeline-riser systems,the resulting stability and effectiveness depend critically on the choice of variables in the associated control model.In this...When using topside choking to eliminate severe slugging in offshore pipeline-riser systems,the resulting stability and effectiveness depend critically on the choice of variables in the associated control model.In this study,both potential process variables and manipulated variables are investigated via manual choking experiments.Monotonicity and linearity are adopted as principles for selecting the optimal variables,and the availability of signals in an offshore field is also considered.Both amplitude-domain and time-domain variables are studied,of which five are recommended as the process variable,while the resistance factor of the choking valve is the optimal manipulated variable;other variables may act as auxiliary variables in the control model.How to determine the set value of the process variable is also discussed.Validation experiments with automatic control show that the optimized variables enable faster stabilization.This study offers a reference for the design of slugging control for offshore fields.展开更多
Statistical characteristics and the classification of the topside ionospheric mid-latitude trough are systemically analyzed,using observations from the Defense Meteorological Satellite Program F18(DMSP-F18)satellite.T...Statistical characteristics and the classification of the topside ionospheric mid-latitude trough are systemically analyzed,using observations from the Defense Meteorological Satellite Program F18(DMSP-F18)satellite.The data was obtained at an altitude of around 860 km in near polar orbit,throughout 2013.Our study identified the auroral boundary based on the in-situ electron density and electron spectrum,allowing us to precisely determine the location of the mid-latitude trough.This differs from most previous works,which only use Total Electron Content(TEC)or in-situ electron density.In our study,the troughs exhibited a higher occurrence rate in local winter than in summer,and extended to lower latitudes with increasing geomagnetic activity.It was found that the ionospheric mid-latitude trough,which is associated with temperature changes or enhanced ion drift,exhibited distinct characteristics.Specifically,the ionospheric mid-latitude troughs related to electron temperature(Te)peak were located more equatorward of auroral oval boundary in winter than in summer.The ionospheric mid-latitude troughs related to Te-maximum were less frequently observed at 60−70°S magnetic latitude and 90−240°E longitude.Furthermore,the troughs related to ion temperature(Ti)maximums were observed at relatively higher latitudes,occurring more frequently in winter.In addition,the troughs related to ion velocity(Vi)maximums could be observed in all seasons.The troughs with the maximum-Ti and maximum-Vi were located closer to the equatorward boundary of the auroral oval at the nightside,and in both hemispheres.This implies that enhanced ion drift velocity contributes to increased collisional frictional heating and enhanced ion temperatures,resulting in a density depletion within the trough region.展开更多
Ingredients: 2 eggs 1/2 teaspoon of salt 100g cornstarch 450g topside of beef sliced into matchstick strips 1/2 cup vegetable oil 3 medium-sized carrots peeled and sliced into matchstick strips 2spring onions cut into...Ingredients: 2 eggs 1/2 teaspoon of salt 100g cornstarch 450g topside of beef sliced into matchstick strips 1/2 cup vegetable oil 3 medium-sized carrots peeled and sliced into matchstick strips 2spring onions cut into 1 inch sections 2 chilies shredded 3 garlic cloves crushed 6 teaspoons of sugar 2 tablespoons of soy sauce 4 tablespoonsof wine vinegar.展开更多
基金supported by the Project of China Offshore Oil Engineering Company(Tianjin)CCL2014CFD。
文摘Because the applications of single-anchor leg mooring yoke systems(SYSs)are rarely studied in the offshore industry,the design of such systems features some uncertainties.This paper investigated the effect of eccentricity on the wear of the topside axial bearing of a SYS.The eccentricity of the topside was verified by on-site inspection,and the axial bearing wear was found to be far more serious than the original design.The contact status between the axial bearing and flange surface was studied on the basis of the actual topside load by using nonlinear finite element analysis.Wear tests of the topside bearing under uniform and eccentric loads were also performed to study the effect of eccentric loads on the wear rate.The key parameters obtained from numerical simulations and experimentation were used to calculate the wear depth via a simplified linear wear model based on the product of the pressure and sliding distance.Results showed that eccentric loads are the main factor responsible for the excessive wear of topside axial bearings.
文摘This paper presents some insights on the state-of-the-art practice that has been utilized recently in the inplace structural strength and fatigue analysis for topsides on deepwater floating platforms such as tension leg plat-form (TLP) and semi-submersibles. Emphases are put on analysis software,geometric and mass modeling,hydro-dynamic loading and its mapping,and analysis procedures. In addition,for the in-place analysis using structure analysis computer system (SACS),the procedure of Visual Basic for Application (VBA) is developed to map AQWA-LINE hydrodynamic loading to the SACS integrated hull/topsides model;for the in-place analysis using structure engineering system analysis model (SESAM),many computer aided applications are made to aid the post-processing. These applications have been used in structural analyses for a few TLP and semi-submersible plat-form topsides,and are briefly introduced in this paper.
基金the financial support received from the China National Key Research and Development Project(Grant No.2022YFC2806202)the Fundamental Research Funds for the Central Universities(Grant No.xtr042024002).
文摘When using topside choking to eliminate severe slugging in offshore pipeline-riser systems,the resulting stability and effectiveness depend critically on the choice of variables in the associated control model.In this study,both potential process variables and manipulated variables are investigated via manual choking experiments.Monotonicity and linearity are adopted as principles for selecting the optimal variables,and the availability of signals in an offshore field is also considered.Both amplitude-domain and time-domain variables are studied,of which five are recommended as the process variable,while the resistance factor of the choking valve is the optimal manipulated variable;other variables may act as auxiliary variables in the control model.How to determine the set value of the process variable is also discussed.Validation experiments with automatic control show that the optimized variables enable faster stabilization.This study offers a reference for the design of slugging control for offshore fields.
基金supported by the National Key R&D Program of China(2022YFF0504400)the National Natural Science Foundation of China(42188101,42274195,42174193)+2 种基金the International Partnership Program Of Chinese Academy of Sciences(Grant No.183311KYSB20200003)the USTC Research Funds of the Double First-Class Initiative(YD2080002013)the Joint Open Fund of Mengcheng National Geophysical Observatory(MENGO-202408).
文摘Statistical characteristics and the classification of the topside ionospheric mid-latitude trough are systemically analyzed,using observations from the Defense Meteorological Satellite Program F18(DMSP-F18)satellite.The data was obtained at an altitude of around 860 km in near polar orbit,throughout 2013.Our study identified the auroral boundary based on the in-situ electron density and electron spectrum,allowing us to precisely determine the location of the mid-latitude trough.This differs from most previous works,which only use Total Electron Content(TEC)or in-situ electron density.In our study,the troughs exhibited a higher occurrence rate in local winter than in summer,and extended to lower latitudes with increasing geomagnetic activity.It was found that the ionospheric mid-latitude trough,which is associated with temperature changes or enhanced ion drift,exhibited distinct characteristics.Specifically,the ionospheric mid-latitude troughs related to electron temperature(Te)peak were located more equatorward of auroral oval boundary in winter than in summer.The ionospheric mid-latitude troughs related to Te-maximum were less frequently observed at 60−70°S magnetic latitude and 90−240°E longitude.Furthermore,the troughs related to ion temperature(Ti)maximums were observed at relatively higher latitudes,occurring more frequently in winter.In addition,the troughs related to ion velocity(Vi)maximums could be observed in all seasons.The troughs with the maximum-Ti and maximum-Vi were located closer to the equatorward boundary of the auroral oval at the nightside,and in both hemispheres.This implies that enhanced ion drift velocity contributes to increased collisional frictional heating and enhanced ion temperatures,resulting in a density depletion within the trough region.
