Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underg...Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underground water seepage flow was taken into account or not. The distribution of displacement field around the multi-arch tunnel, which is influenced by the seepage field, was gained. The result indicates that the settlement values of the vault derived from coupling analysis are bigger when considering the seepage flow effect than that not considering. Through the contrast of arch subsidence quantities calculated by two kinds of computation situations, and the comparison between the calculated and measured value of tunnel vault settlement, it is found that the calculated value(5.7-6.0 mm) derived from considering the seepage effect is more close to the measured value(5.8-6.8 mm). Therefore, it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.展开更多
This article aims to establish a coupled thermo-hydraulic mathematical model for steam network by adopting a set of equations, i.e., the continuity equation, motion equation, energy equation, state equation and enthal...This article aims to establish a coupled thermo-hydraulic mathematical model for steam network by adopting a set of equations, i.e., the continuity equation, motion equation, energy equation, state equation and enthalpy equation and considering the interaction of hydraulic and thermal working conditions. The model is simplified according to steam flow features in pipe networks. The unsteady flow model is simplified to a steady one with considering engineering practice and the solution to the governing equations are obtained by using the standard fourth-order Runge-Kutta method. Many factors of steam flow are generally considered, such as condensability, change of state, friction and heat transfer in the model. It is concluded that coupled iteration can be employed in steam network thermo-hydraulic computation. The numerical results with the model are basically in accordance with practical operation data.展开更多
A method to compute aerothermal-aeroelastic two-way coupling for hypersonic curved panel flutter is proposed. The aero-therrno-elastic governing equations of a simply-supported two dimensional curved panel are develop...A method to compute aerothermal-aeroelastic two-way coupling for hypersonic curved panel flutter is proposed. The aero-therrno-elastic governing equations of a simply-supported two dimensional curved panel are developed based on the von K＇arrn＇an geometrically non-linear theory. The Galerkin approach is used to simplify the equations into discrete forms, which are solved by the fourth-order Ronger-Kutta method. The third-order piston theory is applied to the aerodynamics. The Eck- ert＇s reference temperature method and the panel heat flux formula are used to compute the aerodynamic heat flux. Several important effects are included, namely 1） two-way coupling considering the effect of elastic deformation on aerodynamic heating and aerodynamic heating on stiffness of structure, 2） accumulation of the aerodynamic heating in real cruise, 3） arbitrary, non-uniform, in-plane and through-thickness temperature distributions, and 4） the effect of initial deformation of curved panel on the flight time to the onset of flutter. Compared with the results of aerothermal-aeroelastic one-way coupling, it is revealed that the two-way coupling which induces decrease of the flight time to the onset of flutter is more dangerous. In addition, importance should be attached to this method in actual analysis.展开更多
Permeability is a vital property of rock mass, which is highly affected by tectonic stress and human engineering activities. A comprehensive monitoring of pore pressure and flow rate distributions inside the rock mass...Permeability is a vital property of rock mass, which is highly affected by tectonic stress and human engineering activities. A comprehensive monitoring of pore pressure and flow rate distributions inside the rock mass is very important to elucidate the permeability evolution mechanisms, which is difficult to realize in laboratory, but easy to be achieved in numerical simulations. Therefore, the particle flow code （PFC）, a discrete element method, is used to simulate permeability behaviors of rock materials in this study. Owe to the limitation of the existed solid-fluid coupling algorithm in PFC, an improved flow-coupling algorithm is presented to better reflect the preferential flow in rock fractures. The comparative analysis is conducted between original and improved algorithm when simulating rock permeability evolution during triaxial compression, showing that the improved algorithm can better describe the experimental phenomenon. Furthermore, the evolution of pore pressure and flow rate distribution during the flow process are analyzed by using the improved algorithm. It is concluded that during the steady flow process in the fractured specimen, the pore pressure and flow rate both prefer transmitting through the fractures rather than rock matrix. Based on the results, fractures are divided into the following three types： I） fractures link to both the inlet and outlet, II） fractures only link to the inlet, and III） fractures only link to the outlet. The type I fracture is always the preferential propagating path for both the pore pressure and flow rate. For type II fractures, the pore pressure increases and then becomes steady. However, the flow rate increases first and begins to decrease after the flow reaches the stop end of the fracture and finally vanishes. There is no obvious pore pressure or flow rate concentration within type III fractures.展开更多
基金Project(50490274) supported by the National Natural Science Foundation of ChinaProject(200516) supported by Hunan Transportation Science and Technology
文摘Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underground water seepage flow was taken into account or not. The distribution of displacement field around the multi-arch tunnel, which is influenced by the seepage field, was gained. The result indicates that the settlement values of the vault derived from coupling analysis are bigger when considering the seepage flow effect than that not considering. Through the contrast of arch subsidence quantities calculated by two kinds of computation situations, and the comparison between the calculated and measured value of tunnel vault settlement, it is found that the calculated value(5.7-6.0 mm) derived from considering the seepage effect is more close to the measured value(5.8-6.8 mm). Therefore, it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.
文摘This article aims to establish a coupled thermo-hydraulic mathematical model for steam network by adopting a set of equations, i.e., the continuity equation, motion equation, energy equation, state equation and enthalpy equation and considering the interaction of hydraulic and thermal working conditions. The model is simplified according to steam flow features in pipe networks. The unsteady flow model is simplified to a steady one with considering engineering practice and the solution to the governing equations are obtained by using the standard fourth-order Runge-Kutta method. Many factors of steam flow are generally considered, such as condensability, change of state, friction and heat transfer in the model. It is concluded that coupled iteration can be employed in steam network thermo-hydraulic computation. The numerical results with the model are basically in accordance with practical operation data.
文摘A method to compute aerothermal-aeroelastic two-way coupling for hypersonic curved panel flutter is proposed. The aero-therrno-elastic governing equations of a simply-supported two dimensional curved panel are developed based on the von K＇arrn＇an geometrically non-linear theory. The Galerkin approach is used to simplify the equations into discrete forms, which are solved by the fourth-order Ronger-Kutta method. The third-order piston theory is applied to the aerodynamics. The Eck- ert＇s reference temperature method and the panel heat flux formula are used to compute the aerodynamic heat flux. Several important effects are included, namely 1） two-way coupling considering the effect of elastic deformation on aerodynamic heating and aerodynamic heating on stiffness of structure, 2） accumulation of the aerodynamic heating in real cruise, 3） arbitrary, non-uniform, in-plane and through-thickness temperature distributions, and 4） the effect of initial deformation of curved panel on the flight time to the onset of flutter. Compared with the results of aerothermal-aeroelastic one-way coupling, it is revealed that the two-way coupling which induces decrease of the flight time to the onset of flutter is more dangerous. In addition, importance should be attached to this method in actual analysis.
基金Project（BK20150005） supported by the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars, China Project（2015XKZD05） supported by the Fundamental Research Funds for the Central Universities, China
文摘Permeability is a vital property of rock mass, which is highly affected by tectonic stress and human engineering activities. A comprehensive monitoring of pore pressure and flow rate distributions inside the rock mass is very important to elucidate the permeability evolution mechanisms, which is difficult to realize in laboratory, but easy to be achieved in numerical simulations. Therefore, the particle flow code （PFC）, a discrete element method, is used to simulate permeability behaviors of rock materials in this study. Owe to the limitation of the existed solid-fluid coupling algorithm in PFC, an improved flow-coupling algorithm is presented to better reflect the preferential flow in rock fractures. The comparative analysis is conducted between original and improved algorithm when simulating rock permeability evolution during triaxial compression, showing that the improved algorithm can better describe the experimental phenomenon. Furthermore, the evolution of pore pressure and flow rate distribution during the flow process are analyzed by using the improved algorithm. It is concluded that during the steady flow process in the fractured specimen, the pore pressure and flow rate both prefer transmitting through the fractures rather than rock matrix. Based on the results, fractures are divided into the following three types： I） fractures link to both the inlet and outlet, II） fractures only link to the inlet, and III） fractures only link to the outlet. The type I fracture is always the preferential propagating path for both the pore pressure and flow rate. For type II fractures, the pore pressure increases and then becomes steady. However, the flow rate increases first and begins to decrease after the flow reaches the stop end of the fracture and finally vanishes. There is no obvious pore pressure or flow rate concentration within type III fractures.
