The power-law fluid flow past a row of uniform placed square cylinders is investigated using the Lattice Boltzmann method (LBM).The flow is assumed to be two-dimensional and incompressible.The relaxation time is assum...The power-law fluid flow past a row of uniform placed square cylinders is investigated using the Lattice Boltzmann method (LBM).The flow is assumed to be two-dimensional and incompressible.The relaxation time is assumed to be shear-dependent and determined by using a variable parameter related to the local shear rate.The effects of both shear-thinning/shear-thickening property and the cylinder spacing on the confluence of the jets are mainly concerned.The bifurcation diagrams of the flow are obtained,which include confluences of double and quadruple jets.The results show that both the first and second pitchfork bifurcations are advanced due to the effect of the shear-thinning property,and postponed due to the shear-thickening property.展开更多
Implicit smoothed particle hydrodynamics method has been proposed to overcome the problem that only very small time steps can be used for high viscosity fluids(such as power law fluids)in order to obtain a stable simu...Implicit smoothed particle hydrodynamics method has been proposed to overcome the problem that only very small time steps can be used for high viscosity fluids(such as power law fluids)in order to obtain a stable simulation.However,the pressure field is difficult to simulate correctly with this method because the numerical high-frequency noise on the pressure field cannot be removed.In this study,several improvements,which are the diffusive term in the continuity equation,the artificial viscosity and a simplified physical viscosity term in the momentum equation,are introduced,and a new boundary treatment is also proposed.The linear equations derived from the momentum equation are large-scale,sparse and positive definite but unsymmetrical,therefore,Conjugate Gradient Squared(CGS)is used to solve them.For the purpose of verifying the validity of the proposed method,Poiseuille flows with Newtonian and power law fluids are solved and compared with exact solution and traditional SPH.Drops of different fluid properties impacting a rigid wall are also simulated and compared with VOF solution.All the numerical results obtained by the proposed method agree well with available data.The proposed method shows the higher efficiency than traditional SPH and the less numerical noise on the pressure field and better stability than implicit SPH.展开更多
Nuclear decay is investigated by the view of network science and the relationship of nuclear decay among different radionuclide can be mapped to a network topology directly.The network includes 1410 nodes and 1275 edg...Nuclear decay is investigated by the view of network science and the relationship of nuclear decay among different radionuclide can be mapped to a network topology directly.The network includes 1410 nodes and 1275 edges.The average degree of the network of nuclear decay is about 1.8,the cumulative degree distribution still meets the typical power-law distribution,and the corresponding exponent is about 4.1.Not considering their dynamic behavior,the fitting parameters of the nuclear decay network are obtained according to the LUHNM theory proposed by our group before.Their cumulated degree distributions of the nuclear decay network match well.The idea and method may provide a new way to study some other problems of nuclear physics.展开更多
基金assistance from the Natural Science Foundation of China(GrantNo. 10972115)
文摘The power-law fluid flow past a row of uniform placed square cylinders is investigated using the Lattice Boltzmann method (LBM).The flow is assumed to be two-dimensional and incompressible.The relaxation time is assumed to be shear-dependent and determined by using a variable parameter related to the local shear rate.The effects of both shear-thinning/shear-thickening property and the cylinder spacing on the confluence of the jets are mainly concerned.The bifurcation diagrams of the flow are obtained,which include confluences of double and quadruple jets.The results show that both the first and second pitchfork bifurcations are advanced due to the effect of the shear-thinning property,and postponed due to the shear-thickening property.
基金supported by the National Natural Science Foundation of China(Grant No.51276192)
文摘Implicit smoothed particle hydrodynamics method has been proposed to overcome the problem that only very small time steps can be used for high viscosity fluids(such as power law fluids)in order to obtain a stable simulation.However,the pressure field is difficult to simulate correctly with this method because the numerical high-frequency noise on the pressure field cannot be removed.In this study,several improvements,which are the diffusive term in the continuity equation,the artificial viscosity and a simplified physical viscosity term in the momentum equation,are introduced,and a new boundary treatment is also proposed.The linear equations derived from the momentum equation are large-scale,sparse and positive definite but unsymmetrical,therefore,Conjugate Gradient Squared(CGS)is used to solve them.For the purpose of verifying the validity of the proposed method,Poiseuille flows with Newtonian and power law fluids are solved and compared with exact solution and traditional SPH.Drops of different fluid properties impacting a rigid wall are also simulated and compared with VOF solution.All the numerical results obtained by the proposed method agree well with available data.The proposed method shows the higher efficiency than traditional SPH and the less numerical noise on the pressure field and better stability than implicit SPH.
基金Supported by National Natural Science Foundation of China under Grant Nos. 60874087 and 61174151
文摘Nuclear decay is investigated by the view of network science and the relationship of nuclear decay among different radionuclide can be mapped to a network topology directly.The network includes 1410 nodes and 1275 edges.The average degree of the network of nuclear decay is about 1.8,the cumulative degree distribution still meets the typical power-law distribution,and the corresponding exponent is about 4.1.Not considering their dynamic behavior,the fitting parameters of the nuclear decay network are obtained according to the LUHNM theory proposed by our group before.Their cumulated degree distributions of the nuclear decay network match well.The idea and method may provide a new way to study some other problems of nuclear physics.
