In order to apply physical simulation results to natural gas hydrate reservoir parameters to provide a theoretical framework for the design of a development plan,an analytical equation method was used to obtain the si...In order to apply physical simulation results to natural gas hydrate reservoir parameters to provide a theoretical framework for the design of a development plan,an analytical equation method was used to obtain the similarity criteria of natural gas hydrate reservoir development by physical simulation,based on a mathematical model of natural gas hydrate development.Given the approach of numerical simulation,a sensitivity analysis for all parameters was carried out,which specifically demonstrated that initial temperature is the most important parameter.Parameters of thermal conductivity coefficients are not necessary for conducting the NGH dissociation process,which will fundamentally simplify the design and establishment of the model.The analysis provides a sound theoretical basis and design principles for particular similarity.展开更多
The control equations of gas concentration field in gob areas with a known velocity field are partial differential equations with variable coefficients,whose traditional mathematical calculation methods are very compl...The control equations of gas concentration field in gob areas with a known velocity field are partial differential equations with variable coefficients,whose traditional mathematical calculation methods are very complex.A numerical simulation method can be used to calculate the gas concentration field,but it also needs considerable amounts of computer resources and the relations of gas concentration at different points of the gob area are undefined.Based on the model of stream tubes,the conservation equations of mass and gas components within the stream tube are used to deduce the equations of a gas concentration field in a gob area with a known velocity field.This method of calculation of a gas concentration field is applied in a gob area with a U-type ventilation working face,which suggests that this new method has the virtue of exact calculations is simple to operate and has a clear physical interpretation.展开更多
A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely u...A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck.展开更多
This paper discusses the calculation of plastic zone properties around circular tunnels to rock-masses that satisfy the Hoek–Brown failure criterion in non-hydrostatic condition,and reviews the calculation of plastic...This paper discusses the calculation of plastic zone properties around circular tunnels to rock-masses that satisfy the Hoek–Brown failure criterion in non-hydrostatic condition,and reviews the calculation of plastic zone and displacement,and the basis of the convergence–confinement method in hydrostatic condition.A two-dimensional numerical simulation model was developed to gain understanding of the plastic zone shape.Plastic zone radius in any angles around the tunnel is analyzed and measured,using different values of overburden(four states)and stress ratio(nine states).Plastic zone radius equations were obtained from fitting curve to data which are dependent on the values of stress ratio,angle and plastic zone radius in hydrostatic condition.Finally validation of this equation indicate that results predict the real plastic zone radius appropriately.展开更多
Traditional methods for assessing effective roof support can be difficult to apply to complex three-dimensional excavations. Through worked examples,the approach of combined two-dimensional and three-dimensional numer...Traditional methods for assessing effective roof support can be difficult to apply to complex three-dimensional excavations. Through worked examples,the approach of combined two-dimensional and three-dimensional numerical modeling has been shown to be successful in understanding mechanisms of rock failure for unique excavation geometries and geotechnical properties and,in turn,provides adequate roof support recommendations for complex three-dimensional excavations in Australian coal mines. An interactive approach of monitoring and model review during the excavation process is an important part of model support recommendations to ensure rock failure and deformation in the model are representative of actual conditions,to provide effective and practical controls.展开更多
In the present analysis, several parameters used in a numerical simulation are investigated in an integrated study to obtain their influence on the process and results of this simulation. The parameters studied are el...In the present analysis, several parameters used in a numerical simulation are investigated in an integrated study to obtain their influence on the process and results of this simulation. The parameters studied are element formulation, friction coefficient, and material model. Numerical simulations using the non-linear finite element method are conducted to produce virtual experimental data for several collision scenarios. Pattern and size damages caused by collision in a real accident case are assumed as real experimental data, and these are used to validate the method. The element model study performed indicates that the Belytschko-Tsay element formulation should be recommended for use in virtual experiments. It is recommended that the real value of the friction coefficient for materials involved is applied in simulations. For the study of the material model, the application of materials with high yield strength is recommended for use in the side hull structure.展开更多
Sandwich plate systems (SPS) are advanced materials that have begun to receive extensive attention in naval architecture and ocean engineering.At present, according to the rules of classification societies, a mixture ...Sandwich plate systems (SPS) are advanced materials that have begun to receive extensive attention in naval architecture and ocean engineering.At present, according to the rules of classification societies, a mixture of shell and solid elements are required to simulate an SPS.Based on the principle of stiffness decomposition, a new numerical simulation method for shell elements was proposed.In accordance with the principle of stiffness decomposition, the total stiffness can be decomposed into the bending stiffness and shear stiffness.Displacement and stress response related to bending stiffness was calculated with the laminated shell element.Displacement and stress response due to shear was calculated by use of a computational code write by FORTRAN language.Then the total displacement and stress response for the SPS was obtained by adding together these two parts of total displacement and stress.Finally, a rectangular SPS plate and a double-bottom structure were used for a simulation.The results show that the deflection simulated by the elements proposed in the paper is larger than the same simulated by solid elements and the analytical solution according to Hoff theory and approximate to the same simulated by the mixture of shell-solid elements, and the stress simulated by the elements proposed in the paper is approximate to the other simulating methods.So compared with calculations based on a mixture of shell and solid elements, the numerical simulation method given in the paper is more efficient and easier to do.展开更多
基金supported by the China Petroleum and Chemical Corporation (No.P06070)the National Natural Science Foundation of China (No.50404003)
文摘In order to apply physical simulation results to natural gas hydrate reservoir parameters to provide a theoretical framework for the design of a development plan,an analytical equation method was used to obtain the similarity criteria of natural gas hydrate reservoir development by physical simulation,based on a mathematical model of natural gas hydrate development.Given the approach of numerical simulation,a sensitivity analysis for all parameters was carried out,which specifically demonstrated that initial temperature is the most important parameter.Parameters of thermal conductivity coefficients are not necessary for conducting the NGH dissociation process,which will fundamentally simplify the design and establishment of the model.The analysis provides a sound theoretical basis and design principles for particular similarity.
基金Financial support for this work,provided by the Doctor Startup Foundation of Xi'an University of Science & Technology
文摘The control equations of gas concentration field in gob areas with a known velocity field are partial differential equations with variable coefficients,whose traditional mathematical calculation methods are very complex.A numerical simulation method can be used to calculate the gas concentration field,but it also needs considerable amounts of computer resources and the relations of gas concentration at different points of the gob area are undefined.Based on the model of stream tubes,the conservation equations of mass and gas components within the stream tube are used to deduce the equations of a gas concentration field in a gob area with a known velocity field.This method of calculation of a gas concentration field is applied in a gob area with a U-type ventilation working face,which suggests that this new method has the virtue of exact calculations is simple to operate and has a clear physical interpretation.
基金the National High Technology Research and Development Program of China (863 Program,Grant No.2007AA11Z130)
文摘A numerical model was established for simulating wave impact on a horizontal deck by an improved incompressible smoothed particle hydrodynamics (ISPH). As a grid-less particle method, the ISPH method has been widely used in the free-surface hydrodynamic flows with good accuracy. The improvement includes the employment of a corrective function for enhancement of angular momentum conservation in a particle-based calculation and a new estimation method to predict the pressure on the horizontal deck. The simulation results show a good agreement with the experiment. The present numerical model can be used to study wave impact load on the horizontal deck.
文摘This paper discusses the calculation of plastic zone properties around circular tunnels to rock-masses that satisfy the Hoek–Brown failure criterion in non-hydrostatic condition,and reviews the calculation of plastic zone and displacement,and the basis of the convergence–confinement method in hydrostatic condition.A two-dimensional numerical simulation model was developed to gain understanding of the plastic zone shape.Plastic zone radius in any angles around the tunnel is analyzed and measured,using different values of overburden(four states)and stress ratio(nine states).Plastic zone radius equations were obtained from fitting curve to data which are dependent on the values of stress ratio,angle and plastic zone radius in hydrostatic condition.Finally validation of this equation indicate that results predict the real plastic zone radius appropriately.
文摘Traditional methods for assessing effective roof support can be difficult to apply to complex three-dimensional excavations. Through worked examples,the approach of combined two-dimensional and three-dimensional numerical modeling has been shown to be successful in understanding mechanisms of rock failure for unique excavation geometries and geotechnical properties and,in turn,provides adequate roof support recommendations for complex three-dimensional excavations in Australian coal mines. An interactive approach of monitoring and model review during the excavation process is an important part of model support recommendations to ensure rock failure and deformation in the model are representative of actual conditions,to provide effective and practical controls.
文摘In the present analysis, several parameters used in a numerical simulation are investigated in an integrated study to obtain their influence on the process and results of this simulation. The parameters studied are element formulation, friction coefficient, and material model. Numerical simulations using the non-linear finite element method are conducted to produce virtual experimental data for several collision scenarios. Pattern and size damages caused by collision in a real accident case are assumed as real experimental data, and these are used to validate the method. The element model study performed indicates that the Belytschko-Tsay element formulation should be recommended for use in virtual experiments. It is recommended that the real value of the friction coefficient for materials involved is applied in simulations. For the study of the material model, the application of materials with high yield strength is recommended for use in the side hull structure.
基金Supported by the Fundamental Research Funds for the Central Universities under Grant No.HEUCFR 1003
文摘Sandwich plate systems (SPS) are advanced materials that have begun to receive extensive attention in naval architecture and ocean engineering.At present, according to the rules of classification societies, a mixture of shell and solid elements are required to simulate an SPS.Based on the principle of stiffness decomposition, a new numerical simulation method for shell elements was proposed.In accordance with the principle of stiffness decomposition, the total stiffness can be decomposed into the bending stiffness and shear stiffness.Displacement and stress response related to bending stiffness was calculated with the laminated shell element.Displacement and stress response due to shear was calculated by use of a computational code write by FORTRAN language.Then the total displacement and stress response for the SPS was obtained by adding together these two parts of total displacement and stress.Finally, a rectangular SPS plate and a double-bottom structure were used for a simulation.The results show that the deflection simulated by the elements proposed in the paper is larger than the same simulated by solid elements and the analytical solution according to Hoff theory and approximate to the same simulated by the mixture of shell-solid elements, and the stress simulated by the elements proposed in the paper is approximate to the other simulating methods.So compared with calculations based on a mixture of shell and solid elements, the numerical simulation method given in the paper is more efficient and easier to do.
