利用离散单元法中的二维颗粒流方法(particle flow code in 2-dimension,PFC2D),通过对双轴数值试样施加循环等幅应变且控制加荷过程中试样体积(面积)不变的方法,模拟了循环加荷条件下饱和砂土的液化特性。在得到试样液化宏观力学响应...利用离散单元法中的二维颗粒流方法(particle flow code in 2-dimension,PFC2D),通过对双轴数值试样施加循环等幅应变且控制加荷过程中试样体积(面积)不变的方法,模拟了循环加荷条件下饱和砂土的液化特性。在得到试样液化宏观力学响应的同时,分析了液化过程中内部平均接触数的变化规律。进一步研究了应变幅值、围压对数值试样液化特性的影响,并与室内试验规律进行了对比。结果表明,数值模拟能够定性地反映饱和砂土振动液化的一般规律,数值模拟得到的应变幅值、围压对试样抗液化强度的影响规律符合实际砂土室内试验规律。展开更多
The agglomeration behavior of particles significantly impacts on the defluidization occurring in a fluidized bed during the direct reduction process.The influence of CO/H_(2)ratio on surface diffusion of iron atoms wa...The agglomeration behavior of particles significantly impacts on the defluidization occurring in a fluidized bed during the direct reduction process.The influence of CO/H_(2)ratio on surface diffusion of iron atoms was proposed,and the solid bridge force between iron oxide particles was quantificationally analyzed.Moreover,the solid bridge force was successfully added into a CFD–DEM(computational fluid dynamics–discrete element method)model combined with heat transfer and mass transport to investigate the detailed information of agglomeration in a fluidized bed,including the spatial distribution of temperature,velocity and metallization of iron oxide particles.The region of defluidization is sensitive to the reduction temperature.At the same reduction temperature,the iron oxide powder will perform higher metallization and stable fluidization properties with molar fraction of H_(2)in the range of 0.6–0.8,when iron oxide is reduced by CO/H_(2)mixture.展开更多
In this paper,a new mixedfinite element scheme using element-wise stabilization is introduced for the biharmonic equation with variable coefficient on Lipschitz polyhedral domains.The proposed scheme doesn’t involve ...In this paper,a new mixedfinite element scheme using element-wise stabilization is introduced for the biharmonic equation with variable coefficient on Lipschitz polyhedral domains.The proposed scheme doesn’t involve any integration along mesh interfaces.The gradient of the solution is approximated by H(div)-conforming BDMk+1 element or vector valued Lagrange element with order k+1,while the solution is approximated by Lagrange element with order k+2 for any k≥0.This scheme can be easily implemented and produces symmetric and positive definite linear system.We provide a new discrete H^(2)-norm stability,which is useful not only in analysis of this scheme but also in C^(0) interior penalty methods and DG methods.Optimal convergences in both discrete H^(2)-norm and L^(2)-norm are derived.This scheme with its analysis is further generalized to the von K´arm´an equations.Finally,numerical results verifying the theoretical estimates of the proposed algorithms are also presented.展开更多
文摘利用离散单元法中的二维颗粒流方法(particle flow code in 2-dimension,PFC2D),通过对双轴数值试样施加循环等幅应变且控制加荷过程中试样体积(面积)不变的方法,模拟了循环加荷条件下饱和砂土的液化特性。在得到试样液化宏观力学响应的同时,分析了液化过程中内部平均接触数的变化规律。进一步研究了应变幅值、围压对数值试样液化特性的影响,并与室内试验规律进行了对比。结果表明,数值模拟能够定性地反映饱和砂土振动液化的一般规律,数值模拟得到的应变幅值、围压对试样抗液化强度的影响规律符合实际砂土室内试验规律。
基金the National Natural Science Foundation Project of China(51374263 and 51974046).
文摘The agglomeration behavior of particles significantly impacts on the defluidization occurring in a fluidized bed during the direct reduction process.The influence of CO/H_(2)ratio on surface diffusion of iron atoms was proposed,and the solid bridge force between iron oxide particles was quantificationally analyzed.Moreover,the solid bridge force was successfully added into a CFD–DEM(computational fluid dynamics–discrete element method)model combined with heat transfer and mass transport to investigate the detailed information of agglomeration in a fluidized bed,including the spatial distribution of temperature,velocity and metallization of iron oxide particles.The region of defluidization is sensitive to the reduction temperature.At the same reduction temperature,the iron oxide powder will perform higher metallization and stable fluidization properties with molar fraction of H_(2)in the range of 0.6–0.8,when iron oxide is reduced by CO/H_(2)mixture.
基金supported by the NSF of China(Grant No.12122115,11771363)supported by IITB Chair Professor’s fund and also partly by a MATRIX Grant No.MTR/201S/000309(SERB,DST,Govt.India)supported by a grant fromthe Research Grants Council of the Hong Kong Special Administrative Region,China(Project No.CityU 11302219).
文摘In this paper,a new mixedfinite element scheme using element-wise stabilization is introduced for the biharmonic equation with variable coefficient on Lipschitz polyhedral domains.The proposed scheme doesn’t involve any integration along mesh interfaces.The gradient of the solution is approximated by H(div)-conforming BDMk+1 element or vector valued Lagrange element with order k+1,while the solution is approximated by Lagrange element with order k+2 for any k≥0.This scheme can be easily implemented and produces symmetric and positive definite linear system.We provide a new discrete H^(2)-norm stability,which is useful not only in analysis of this scheme but also in C^(0) interior penalty methods and DG methods.Optimal convergences in both discrete H^(2)-norm and L^(2)-norm are derived.This scheme with its analysis is further generalized to the von K´arm´an equations.Finally,numerical results verifying the theoretical estimates of the proposed algorithms are also presented.
