The multiscale transport mechanism of methane in unconventional reservoirs is dominated by slip and transition flows resulting from the ultra-low permeability of micro/nano-scale pores,which requires consideration of ...The multiscale transport mechanism of methane in unconventional reservoirs is dominated by slip and transition flows resulting from the ultra-low permeability of micro/nano-scale pores,which requires consideration of the microscale and rarefaction effects.Traditional continuum-based computational fluid dynamics(CFD)becomes problematic when modeling micro-gaseous flow in these multiscale pore networks because of its disadvantages in the treatment of cases with a complicated boundary.As an alternative,the lattice Boltzmann method(LBM),a special discrete form of the Boltzmann equation,has been widely applied to model the multi-scale and multi-mechanism flows in unconventional reservoirs,considering its mesoscopic nature and advantages in simulating gas flows in complex porous media.Consequently,numerous LBM models and slip boundary schemes have been proposed and reported in the literature.This study investigates the predominately reported LBM models and kinetic boundary schemes.The results of these LBM models systematically compare to existing experimental results,analytical solutions of Navier-Stokes,solutions of the Boltzmann equation,direct simulation of Monte Carlo(DSMC)and information-preservation DSMC(IP_DSMC)results,as well as the numerical results of the linearized Boltzmann equation by the discrete velocity method(DVM).The results point out the challenges and limitations of existing multiple-relaxation-times LBM models in predicting micro-gaseous flow in unconventional reservoirs.展开更多
The potential energy in materials is well approximated by pair functional which is composed of pair potentials and embedding energy. During calculating material potential energy, the orientational component and the vo...The potential energy in materials is well approximated by pair functional which is composed of pair potentials and embedding energy. During calculating material potential energy, the orientational component and the volumetric component are derived respectively from pair potentials and embedding energy. The sum of energy of all these two kinds of components is the material potential. No matter how microstructures change, damage or fracture, at the most level, they are all the changing and breaking atomic bonds. As an abstract of atomic bonds, these components change their stiffness during damaging. Material constitutive equations have been formulated by means of assembling all components' response functions. This material model is called the component assembling model. Theoretical analysis and numerical computing indicate that the proposed model has the capacity of reproducing some results satisfactorily, with the advantages of great conceptual simplicity, physical explicitness, and intrinsic induced anisotropy, etc.展开更多
基金supported by the Strategic Program of Chinese Academy of Sciences (Grant No. XDB10030400)the Hundred Talent Program of Chinese Academy of Sciences (Grant No. Y323081C01)The National Natural Science Fund (Grant No. 51439008)
文摘The multiscale transport mechanism of methane in unconventional reservoirs is dominated by slip and transition flows resulting from the ultra-low permeability of micro/nano-scale pores,which requires consideration of the microscale and rarefaction effects.Traditional continuum-based computational fluid dynamics(CFD)becomes problematic when modeling micro-gaseous flow in these multiscale pore networks because of its disadvantages in the treatment of cases with a complicated boundary.As an alternative,the lattice Boltzmann method(LBM),a special discrete form of the Boltzmann equation,has been widely applied to model the multi-scale and multi-mechanism flows in unconventional reservoirs,considering its mesoscopic nature and advantages in simulating gas flows in complex porous media.Consequently,numerous LBM models and slip boundary schemes have been proposed and reported in the literature.This study investigates the predominately reported LBM models and kinetic boundary schemes.The results of these LBM models systematically compare to existing experimental results,analytical solutions of Navier-Stokes,solutions of the Boltzmann equation,direct simulation of Monte Carlo(DSMC)and information-preservation DSMC(IP_DSMC)results,as well as the numerical results of the linearized Boltzmann equation by the discrete velocity method(DVM).The results point out the challenges and limitations of existing multiple-relaxation-times LBM models in predicting micro-gaseous flow in unconventional reservoirs.
基金Supported by the National Natural Science Foundation of China (Grant Nos.10572140 and 10232050)the Ministry of Science and Technology Foundation (Grant No.2002CB412706) are short of physical basics, and which is particularly evident in anisotropic damage theories.
文摘The potential energy in materials is well approximated by pair functional which is composed of pair potentials and embedding energy. During calculating material potential energy, the orientational component and the volumetric component are derived respectively from pair potentials and embedding energy. The sum of energy of all these two kinds of components is the material potential. No matter how microstructures change, damage or fracture, at the most level, they are all the changing and breaking atomic bonds. As an abstract of atomic bonds, these components change their stiffness during damaging. Material constitutive equations have been formulated by means of assembling all components' response functions. This material model is called the component assembling model. Theoretical analysis and numerical computing indicate that the proposed model has the capacity of reproducing some results satisfactorily, with the advantages of great conceptual simplicity, physical explicitness, and intrinsic induced anisotropy, etc.
