Mooring system plays an important role in station keeping of floating offshore structures. Coupled analysis on mooring-buoy interactions has been increasingly studied in recent years. At present, chains and wire ropes...Mooring system plays an important role in station keeping of floating offshore structures. Coupled analysis on mooring-buoy interactions has been increasingly studied in recent years. At present, chains and wire ropes are widely used in offshore engineering practice. On the basis of mooring line statics, an explicit formulation of single mooring chain/wire rope stiffness coefficients and mooring stiffness matrix of the mooring system were derived in this article, taking into account the horizontal restoring force, vertical restoring force and their coupling terms. The nonlinearity of mooring stiffness was analyzed, and the influences of various parameters, such as material, displacement, pre-tension and water depth, were investigated. Finally some application cases of the mooring stiffness in hydrodynamic calculation were presented. Data shows that this kind of stiffness can reckon in linear and nonlinear forces of mooring system. Also, the stiffness can be used in hydrodynamic analysis to get the eieenfrequencv of slow drift motions.展开更多
The model of pressure solution for granular aggregate was introduced into the FEM code for analysis of thermo-hydro- mechanical （T-H-M） coupling in porous medium. Aiming at a hypothetical nuclear waste repository in...The model of pressure solution for granular aggregate was introduced into the FEM code for analysis of thermo-hydro- mechanical （T-H-M） coupling in porous medium. Aiming at a hypothetical nuclear waste repository in an unsaturated quartz rock mass, two computation conditions were designed： 1） the porosity and the permeability of rock mass are fimctions of pressure solution; 2） the porosity and the permeability are constants. Then the corresponding numerical simulations for a disposal period of 4 a were carried out, and the states of temperatures, porosities and permeabilities, pore pressures, flow velocities and stresses in the rock mass were investigated. The results show that at the end of the calculation in Case 1, pressure solution makes the porosities and the permeabilities decrease to 10%-45% and 0.05%-1.4% of their initial values, respectively. Under the action of the release heat of nuclear waste, the negative pore pressures both in Case 1 and Case 2 are 1.2-1.4 and 1.01-l.06 times of the initial values, respectively. So, the former represents an obvious effect of pressure solution. The magnitudes and distributions of stresses within the rock mass in the two calculation cases are the same.展开更多
Boiling heat transfer condition has significance for pool-type research reactors cooled by natural circulation.It has important effect on the fuel element safety of reactor.On the basis of heat transfer characteristic...Boiling heat transfer condition has significance for pool-type research reactors cooled by natural circulation.It has important effect on the fuel element safety of reactor.On the basis of heat transfer characteristics of the Xi'an pulsed reactor(XAPR),fuel conduction,single-phase convection and boiling heat transfer,and void fraction models of the core are constructed.To validate the correctness of the physical models presented in the paper,numerical calculation based on a subchannel analysis method of XAPR is carried out,and the temperature fields are measured in some reactor coolant channels.The comparison between the calculated and experimental results verifies the effectiveness of the models.These physical models are used to calculate the thermal-hydraulic parameters of XAPR at the rated power(for XAPR the rated power is 2.0 MW in steady-state operation).The results indicate that subcooled boiling occurs in the XAPR core but it exhibits a subcooling degree which is considerably higher than that of saturation boiling.Subcooled boiling improves the efficiency of heat transfer between the fuel element surface and coolant,as well as effectively protects fuel elements.This research is also a beneficial reference in thermal-hydraulic analysis for other natural circulation reactors.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.（51079034）.
文摘Mooring system plays an important role in station keeping of floating offshore structures. Coupled analysis on mooring-buoy interactions has been increasingly studied in recent years. At present, chains and wire ropes are widely used in offshore engineering practice. On the basis of mooring line statics, an explicit formulation of single mooring chain/wire rope stiffness coefficients and mooring stiffness matrix of the mooring system were derived in this article, taking into account the horizontal restoring force, vertical restoring force and their coupling terms. The nonlinearity of mooring stiffness was analyzed, and the influences of various parameters, such as material, displacement, pre-tension and water depth, were investigated. Finally some application cases of the mooring stiffness in hydrodynamic calculation were presented. Data shows that this kind of stiffness can reckon in linear and nonlinear forces of mooring system. Also, the stiffness can be used in hydrodynamic analysis to get the eieenfrequencv of slow drift motions.
基金Project(2010CB732101) supported by the National Basic Research Program of ChinaProject(51079145) supported by the National Natural Science Foundation of ChinaProject(2009BAK53B03) supported by the National Key Technology R&D Program of China
文摘The model of pressure solution for granular aggregate was introduced into the FEM code for analysis of thermo-hydro- mechanical （T-H-M） coupling in porous medium. Aiming at a hypothetical nuclear waste repository in an unsaturated quartz rock mass, two computation conditions were designed： 1） the porosity and the permeability of rock mass are fimctions of pressure solution; 2） the porosity and the permeability are constants. Then the corresponding numerical simulations for a disposal period of 4 a were carried out, and the states of temperatures, porosities and permeabilities, pore pressures, flow velocities and stresses in the rock mass were investigated. The results show that at the end of the calculation in Case 1, pressure solution makes the porosities and the permeabilities decrease to 10%-45% and 0.05%-1.4% of their initial values, respectively. Under the action of the release heat of nuclear waste, the negative pore pressures both in Case 1 and Case 2 are 1.2-1.4 and 1.01-l.06 times of the initial values, respectively. So, the former represents an obvious effect of pressure solution. The magnitudes and distributions of stresses within the rock mass in the two calculation cases are the same.
文摘Boiling heat transfer condition has significance for pool-type research reactors cooled by natural circulation.It has important effect on the fuel element safety of reactor.On the basis of heat transfer characteristics of the Xi'an pulsed reactor(XAPR),fuel conduction,single-phase convection and boiling heat transfer,and void fraction models of the core are constructed.To validate the correctness of the physical models presented in the paper,numerical calculation based on a subchannel analysis method of XAPR is carried out,and the temperature fields are measured in some reactor coolant channels.The comparison between the calculated and experimental results verifies the effectiveness of the models.These physical models are used to calculate the thermal-hydraulic parameters of XAPR at the rated power(for XAPR the rated power is 2.0 MW in steady-state operation).The results indicate that subcooled boiling occurs in the XAPR core but it exhibits a subcooling degree which is considerably higher than that of saturation boiling.Subcooled boiling improves the efficiency of heat transfer between the fuel element surface and coolant,as well as effectively protects fuel elements.This research is also a beneficial reference in thermal-hydraulic analysis for other natural circulation reactors.
