The Z–S–C multiphase lattice Boltzmann model [Zheng, Shu, and Chew(ZSC), J. Comput. Phys. 218, 353(2006)]is favored due to its good stability, high efficiency, and large density ratio. However, in terms of mass cons...The Z–S–C multiphase lattice Boltzmann model [Zheng, Shu, and Chew(ZSC), J. Comput. Phys. 218, 353(2006)]is favored due to its good stability, high efficiency, and large density ratio. However, in terms of mass conservation, this model is not satisfactory during the simulation computations. In this paper, a mass correction is introduced into the ZSC model to make up the mass leakage, while a high-order difference is used to calculate the gradient of the order parameter to improve the accuracy. To verify the improved model, several three-dimensional multiphase flow simulations are carried out,including a bubble in a stationary flow, the merging of two bubbles, and the bubble rising under buoyancy. The numerical simulations show that the results from the present model are in good agreement with those from previous experiments and simulations. The present model not only retains the good properties of the original ZSC model, but also achieves the mass conservation and higher accuracy.展开更多
Coal rock is a type of dual-porosity medium,which is composed of matrix pores and fracture-cutting matrix.They play different roles in the seepage and storage capacity of coal rock.Therefore,constructing the micropore...Coal rock is a type of dual-porosity medium,which is composed of matrix pores and fracture-cutting matrix.They play different roles in the seepage and storage capacity of coal rock.Therefore,constructing the micropore structure of coal rock is very important in the exploration and development of coalbed methane.In this study,we use a coal rock digital core and three-dimensional modeling to study the pore structure of coal rock.First,the micropore structure of coal rock is quantitatively analyzed using a two-dimensional thin-section image,and the quantitative information of the pore and fracture(cleat)structure in the coal rock is extracted.The mean value and standard deviation of the face porosity and pore radius are obtained using statistical analysis.The number of pores is determined using dichotomy and spherical random-packing methods based on compression.By combining with the results of the petrophysical analysis,the single-porosity structure model of the coal rock is obtained using a nonequal-diameter sphere to represent the pores of the coal rock.Then,an ellipsoid with an aspect ratio that is very much lesser than one is used to represent the fracture(cleat)in the coal rock,and a dual-pore structure model of the coal rock is obtained.On this basis,the relationship between the different pore aspect ratios and porosity is explored,and a fitting relationship is obtained.The results show that a nonlinear relationship exists between them.The relationship model can provide a basis for the prediction of coal rock pore structure and the pore structure parameters and provide a reference for understanding the internal structure of coalbed methane reservoirs.展开更多
随着斜拉桥跨度的增大,斜拉索长度也越来越长,但安装位置存在变相折减,导致阻尼器所能提供的阻尼比降低,这给斜拉索减振阻尼器的设计带来了新的挑战。采用数值方法研究了粘滞惯质阻尼器(Viscous Inertial Mass Damper,VIMD)的斜拉索减...随着斜拉桥跨度的增大,斜拉索长度也越来越长,但安装位置存在变相折减,导致阻尼器所能提供的阻尼比降低,这给斜拉索减振阻尼器的设计带来了新的挑战。采用数值方法研究了粘滞惯质阻尼器(Viscous Inertial Mass Damper,VIMD)的斜拉索减振效果。首先,建立了两端点不处于同一水平高度的斜拉索面内运动微分方程,采用有限差分法对运动方程进行数值求解。然后,以苏通大桥A30号斜拉索为工程背景,对比分析了在惯性质量和阻尼系数这两个参数影响下张紧弦模型和斜拉索模型差异,研究了各参数对三维斜拉索-VIMD系统模态阻尼比的影响。研究结果表明:将联惯质单元并联连入传统粘滞阻尼器,可有效提高斜拉索的模态阻尼比;斜拉索-VIMD系统的动力特性分析可由张紧弦-VIMD系统代替,由于拉索倾角和阻尼器空间位置影响,二者之间存在倍数关系。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11862003 and 81860635)the Key Project of the Natural Science Foundation of Guangxi Zhuang Autonomous Region,China(Grant No.2017GXNSFDA198038)+3 种基金the Project of Natural Science Foundation of Guangxi Zhuang Autonomous Region,China(Grant No.2018GXNSFAA281302)the Project for Promotion of Young and Middle-aged Teachers’Basic Scientific Research Ability in Guangxi Universities,China(Grant No.2019KY0084)the“Bagui Scholar”Teams for Innovation and Research Project of Guangxi Zhuang Autonomous Region,Chinathe Graduate Innovation Program of Guangxi Normal University,China(Grant No.JXYJSKT-2019-007)。
文摘The Z–S–C multiphase lattice Boltzmann model [Zheng, Shu, and Chew(ZSC), J. Comput. Phys. 218, 353(2006)]is favored due to its good stability, high efficiency, and large density ratio. However, in terms of mass conservation, this model is not satisfactory during the simulation computations. In this paper, a mass correction is introduced into the ZSC model to make up the mass leakage, while a high-order difference is used to calculate the gradient of the order parameter to improve the accuracy. To verify the improved model, several three-dimensional multiphase flow simulations are carried out,including a bubble in a stationary flow, the merging of two bubbles, and the bubble rising under buoyancy. The numerical simulations show that the results from the present model are in good agreement with those from previous experiments and simulations. The present model not only retains the good properties of the original ZSC model, but also achieves the mass conservation and higher accuracy.
基金sponsored by the National Natural Science Foundation of China(No.41274129)National Science and Technology Major Project(No.2016ZX05026001-004)+2 种基金Key Research and Development Program of Sichuan Province(No.2020YFG0157)the 2018 Central Supporting Local Coconstruction Fund(No.80000-18Z0140504)the Construction and Development of Universities in 2019-Joint Support for Geophysics(Double First-Class center,80000-19Z0204).
文摘Coal rock is a type of dual-porosity medium,which is composed of matrix pores and fracture-cutting matrix.They play different roles in the seepage and storage capacity of coal rock.Therefore,constructing the micropore structure of coal rock is very important in the exploration and development of coalbed methane.In this study,we use a coal rock digital core and three-dimensional modeling to study the pore structure of coal rock.First,the micropore structure of coal rock is quantitatively analyzed using a two-dimensional thin-section image,and the quantitative information of the pore and fracture(cleat)structure in the coal rock is extracted.The mean value and standard deviation of the face porosity and pore radius are obtained using statistical analysis.The number of pores is determined using dichotomy and spherical random-packing methods based on compression.By combining with the results of the petrophysical analysis,the single-porosity structure model of the coal rock is obtained using a nonequal-diameter sphere to represent the pores of the coal rock.Then,an ellipsoid with an aspect ratio that is very much lesser than one is used to represent the fracture(cleat)in the coal rock,and a dual-pore structure model of the coal rock is obtained.On this basis,the relationship between the different pore aspect ratios and porosity is explored,and a fitting relationship is obtained.The results show that a nonlinear relationship exists between them.The relationship model can provide a basis for the prediction of coal rock pore structure and the pore structure parameters and provide a reference for understanding the internal structure of coalbed methane reservoirs.
文摘随着斜拉桥跨度的增大,斜拉索长度也越来越长,但安装位置存在变相折减,导致阻尼器所能提供的阻尼比降低,这给斜拉索减振阻尼器的设计带来了新的挑战。采用数值方法研究了粘滞惯质阻尼器(Viscous Inertial Mass Damper,VIMD)的斜拉索减振效果。首先,建立了两端点不处于同一水平高度的斜拉索面内运动微分方程,采用有限差分法对运动方程进行数值求解。然后,以苏通大桥A30号斜拉索为工程背景,对比分析了在惯性质量和阻尼系数这两个参数影响下张紧弦模型和斜拉索模型差异,研究了各参数对三维斜拉索-VIMD系统模态阻尼比的影响。研究结果表明:将联惯质单元并联连入传统粘滞阻尼器,可有效提高斜拉索的模态阻尼比;斜拉索-VIMD系统的动力特性分析可由张紧弦-VIMD系统代替,由于拉索倾角和阻尼器空间位置影响,二者之间存在倍数关系。
