With the rapid increase of the number and influence of floating population in China,it is urgently needed to understand the regional types of China＇s floating population and their spatial characteristics. After revie...With the rapid increase of the number and influence of floating population in China,it is urgently needed to understand the regional types of China＇s floating population and their spatial characteristics. After reviewing the current methods for identifying regional types of floating population,this paper puts forward a new composite-index identification method and its modification version which is consisted of two indexes of the net migration rate and gross migration rate. Then,the traditional single-index and the new composite-index identification methods are empirically tested to explore their spatial patterns and characteristics by using China＇s 2000 census data at county level. The results show：（1） The composite-index identification method is much better than traditional single-index method because it can measure the migration direction and scale of floating simultaneously,and in particular it can identify the unique regional types of floating population with large scale of immigration and emigration. （2） The modified composite-index identification method,by using the share of a region＇s certain type of floating population to the total in China as weights,can effectively correct the over-or under-estimated errors due to the rather large or small total population of a region. （3） The spatial patterns of different regional types of China＇s floating population are closely related to the regional differentiation of their natural environment,population density and socio-economic development level. The three active regional types of floating population are mainly located in the eastern part of China with lower elevation,more than 800 mm precipitation,rather higher population densities and economic development levels.展开更多
The floating offshore wind turbine(FOWT) is widely used for harvesting marine wind energy. Its dynamic responses under offshore wind and wave environment provide essential reference for the design and installation. In...The floating offshore wind turbine(FOWT) is widely used for harvesting marine wind energy. Its dynamic responses under offshore wind and wave environment provide essential reference for the design and installation. In this study,the dynamic responses of a 6 MW Spar type FOWT designed for the water depth of 100 m are investigated by means of the wave tank experiment and numerical analysis. A scaled model is manufactured for the experiment at a ratio of65.3, while the numerical model is constructed on the open-source platform FAST(Fatigue, Aerodynamics,Structures, and Turbulence). Still water tests, wind-induced only tests, wave-induced only tests and combined windwave-current tests are all conducted experimentally and numerically. The accuracy of the experimental set-up as well as the loading generation has been verified. Surge, pitch and heave motions are selected to analyze and the numerical results agree well with the experimental values. Even though results obtained by using the FOWT calculation model established in FAST software show some deviations from the test results, the trends are always consistent. Both experimental and numerical studies demonstrate that they are reliable for the designed 6 MW Spar type FOWT.展开更多
Tower, Spar platform and mooring system are designed in the project based on a given 6-MW wind turbine. Under wind-induced only, wave-induced only and combined wind and wave induced loads, dynamic response is analyzed...Tower, Spar platform and mooring system are designed in the project based on a given 6-MW wind turbine. Under wind-induced only, wave-induced only and combined wind and wave induced loads, dynamic response is analyzed for a 6-MW Spar-type floating offshore wind turbine （FOWT） under operating conditions and parked conditions respectively. Comparison with a platform-fixed system （land-based system） ofa 6-MW wind turbine is carried out as well. Results demonstrate that the maximal out-of-plane deflection of the blade of a Spar-type system is 3.1% larger than that of a land-based system; the maximum response value of the nacelle acceleration is 215% larger for all the designed load cases being considered; the ultimate tower base fore-aft bending moment of the Spar-type system is 92% larger than that of the land-based system in all of the Design Load Cases （DLCs） being considered; the fluctuations of the mooring tension is mainly wave-induced, and the safety factor of the mooring tension is adequate for the 6-MW FOWT. The results can provide relevant modifications to the initial design for the Spar-type system, the detailed design and model basin test of the 6-MW Spar-type system.展开更多
Both numerical calculation and model test are important techniques to study and forecast the dynamic responses of the floating offshore wind turbine(FOWT). However, both the methods have their own limitations at prese...Both numerical calculation and model test are important techniques to study and forecast the dynamic responses of the floating offshore wind turbine(FOWT). However, both the methods have their own limitations at present. In this study, the dynamic responses of a 5 MW OC3 spar-type floating wind turbine designed for a water depth of 200 m are numerically investigated and validated by a 1:50 scaled model test. Moreover, the discrepancies between the numerical calculations and model tests are obtained and discussed. According to the discussions, it is found that the surge and pitch are coupled with the mooring tensions, but the heave is independent of them. Surge and pitch are mainly induced by wave under wind wave conditions. Wind and current will induce the low-frequency average responses, while wave will induce the fluctuation ranges of the responses. In addition, wave will induce the wavefrequency responses but wind and current will restrain the ranges of the responses.展开更多
This paper addresses joint wind-wave induced dynamic responses of a semi-type offshore floating wind turbine（OFWT） under normal states and fault event conditions. The analysis in this paper is conducted in time doma...This paper addresses joint wind-wave induced dynamic responses of a semi-type offshore floating wind turbine（OFWT） under normal states and fault event conditions. The analysis in this paper is conducted in time domain, using an aero-hydro-servo-elastic simulation code-FAST. Owing to the unique viscous features of the reference system, the original viscous damping model implemented in FAST is replaced with a quadratic one to gain an accurate capture of viscous effects. Simulation cases involve free-decay motion in still water, steady motions in the presence of regular waves and wind as well as dynamic response in operational sea states with and without wind. Simulations also include the cases for transient responses induced by fast blade pitching after emergency shutdown. The features of platform motions, local structural loads and a typical mooring line tension force under a variety of excitations are obtained and investigated.展开更多
In this paper, the seismic response of a newly designed steel jacket offshore platform with a float over deck （FOD） system in the Persian Gulf was investigated through incremental dynamic analysis. Comparison of inc...In this paper, the seismic response of a newly designed steel jacket offshore platform with a float over deck （FOD） system in the Persian Gulf was investigated through incremental dynamic analysis. Comparison of incremental dynamic analysis results for both directions of the platform shows that the lateral strength of the platform in the float over direction is less than its lateral strength in other direction. Dynamic characteristics measurement of a scale model of platform was also performed using forced vibration tests. From experimental measurement of the scaled model, it was observed that dynamic characteristic of the platform is different in the float over direction compared to the other direction. Therefore, a new offshore installed bracing system for the float over direction was proposed for improvement of seismic performance of this type of platform. Finally, the structure with the modified system was assessed using the probabilistic seismic assessment method as well as experimental measurement of its dynamic characteristics. It was observed that the proposed offshore installed bracing system improves the performance of platforms subjected to strong ground motion.展开更多
基金Foundation： Knowledge Innovation Program of the Chinese Academy of Sciences, No.KZCX2-YW-322, National Natural Science Foundation of China, No.40971102 The National Science and Technology Support Plan, No.2006BAJ11B02-04
文摘With the rapid increase of the number and influence of floating population in China,it is urgently needed to understand the regional types of China＇s floating population and their spatial characteristics. After reviewing the current methods for identifying regional types of floating population,this paper puts forward a new composite-index identification method and its modification version which is consisted of two indexes of the net migration rate and gross migration rate. Then,the traditional single-index and the new composite-index identification methods are empirically tested to explore their spatial patterns and characteristics by using China＇s 2000 census data at county level. The results show：（1） The composite-index identification method is much better than traditional single-index method because it can measure the migration direction and scale of floating simultaneously,and in particular it can identify the unique regional types of floating population with large scale of immigration and emigration. （2） The modified composite-index identification method,by using the share of a region＇s certain type of floating population to the total in China as weights,can effectively correct the over-or under-estimated errors due to the rather large or small total population of a region. （3） The spatial patterns of different regional types of China＇s floating population are closely related to the regional differentiation of their natural environment,population density and socio-economic development level. The three active regional types of floating population are mainly located in the eastern part of China with lower elevation,more than 800 mm precipitation,rather higher population densities and economic development levels.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51809170 and 51879160)the National Key R&D Program of China (Grant No. 2019YFB1503700)+1 种基金Program for Intergovernmental International S&T Cooperation Projects of Shanghai Municipality (Grant Nos.19160713600 and 18160744000)the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning (Grant Nos. ZXDF010037 and ZXDF010040)。
文摘The floating offshore wind turbine(FOWT) is widely used for harvesting marine wind energy. Its dynamic responses under offshore wind and wave environment provide essential reference for the design and installation. In this study,the dynamic responses of a 6 MW Spar type FOWT designed for the water depth of 100 m are investigated by means of the wave tank experiment and numerical analysis. A scaled model is manufactured for the experiment at a ratio of65.3, while the numerical model is constructed on the open-source platform FAST(Fatigue, Aerodynamics,Structures, and Turbulence). Still water tests, wind-induced only tests, wave-induced only tests and combined windwave-current tests are all conducted experimentally and numerically. The accuracy of the experimental set-up as well as the loading generation has been verified. Surge, pitch and heave motions are selected to analyze and the numerical results agree well with the experimental values. Even though results obtained by using the FOWT calculation model established in FAST software show some deviations from the test results, the trends are always consistent. Both experimental and numerical studies demonstrate that they are reliable for the designed 6 MW Spar type FOWT.
基金financially supported by the National Basic Research Program of China(973 Program,Grant No.2014CB046205)
文摘Tower, Spar platform and mooring system are designed in the project based on a given 6-MW wind turbine. Under wind-induced only, wave-induced only and combined wind and wave induced loads, dynamic response is analyzed for a 6-MW Spar-type floating offshore wind turbine （FOWT） under operating conditions and parked conditions respectively. Comparison with a platform-fixed system （land-based system） ofa 6-MW wind turbine is carried out as well. Results demonstrate that the maximal out-of-plane deflection of the blade of a Spar-type system is 3.1% larger than that of a land-based system; the maximum response value of the nacelle acceleration is 215% larger for all the designed load cases being considered; the ultimate tower base fore-aft bending moment of the Spar-type system is 92% larger than that of the land-based system in all of the Design Load Cases （DLCs） being considered; the fluctuations of the mooring tension is mainly wave-induced, and the safety factor of the mooring tension is adequate for the 6-MW FOWT. The results can provide relevant modifications to the initial design for the Spar-type system, the detailed design and model basin test of the 6-MW Spar-type system.
基金financially supported by the State Key Laboratory of Ocean Engineering in Shanghai Jiao Tong University and the National Science and Technology Major Project of China(Grant No.2016ZX05028-002-004)
文摘Both numerical calculation and model test are important techniques to study and forecast the dynamic responses of the floating offshore wind turbine(FOWT). However, both the methods have their own limitations at present. In this study, the dynamic responses of a 5 MW OC3 spar-type floating wind turbine designed for a water depth of 200 m are numerically investigated and validated by a 1:50 scaled model test. Moreover, the discrepancies between the numerical calculations and model tests are obtained and discussed. According to the discussions, it is found that the surge and pitch are coupled with the mooring tensions, but the heave is independent of them. Surge and pitch are mainly induced by wave under wind wave conditions. Wind and current will induce the low-frequency average responses, while wave will induce the fluctuation ranges of the responses. In addition, wave will induce the wavefrequency responses but wind and current will restrain the ranges of the responses.
基金financially supported by the National Natural Science Foundation of China(Grant No.51239007)
文摘This paper addresses joint wind-wave induced dynamic responses of a semi-type offshore floating wind turbine（OFWT） under normal states and fault event conditions. The analysis in this paper is conducted in time domain, using an aero-hydro-servo-elastic simulation code-FAST. Owing to the unique viscous features of the reference system, the original viscous damping model implemented in FAST is replaced with a quadratic one to gain an accurate capture of viscous effects. Simulation cases involve free-decay motion in still water, steady motions in the presence of regular waves and wind as well as dynamic response in operational sea states with and without wind. Simulations also include the cases for transient responses induced by fast blade pitching after emergency shutdown. The features of platform motions, local structural loads and a typical mooring line tension force under a variety of excitations are obtained and investigated.
基金sponsored by POGC (Pars Oil and Gas Company,No.132 "Investigation of Structural Health Monitoring of Steel Jacket Offshore Platforms")The financial support of POGC is gratefully acknowledged
文摘In this paper, the seismic response of a newly designed steel jacket offshore platform with a float over deck （FOD） system in the Persian Gulf was investigated through incremental dynamic analysis. Comparison of incremental dynamic analysis results for both directions of the platform shows that the lateral strength of the platform in the float over direction is less than its lateral strength in other direction. Dynamic characteristics measurement of a scale model of platform was also performed using forced vibration tests. From experimental measurement of the scaled model, it was observed that dynamic characteristic of the platform is different in the float over direction compared to the other direction. Therefore, a new offshore installed bracing system for the float over direction was proposed for improvement of seismic performance of this type of platform. Finally, the structure with the modified system was assessed using the probabilistic seismic assessment method as well as experimental measurement of its dynamic characteristics. It was observed that the proposed offshore installed bracing system improves the performance of platforms subjected to strong ground motion.
