In order to investigate the influence of the entrance effect on the spatial distribution of phases, the experiments on gas-liquid two-phase slug flow in a vertical pipe of 0.03m ID were carried out by using optical pr...In order to investigate the influence of the entrance effect on the spatial distribution of phases, the experiments on gas-liquid two-phase slug flow in a vertical pipe of 0.03m ID were carried out by using optical probes and an EKTAPRO 1000 high speed motion analyzer. It demonstrates that the radial profile of slug flow void fraction is parabolic. Influenced by the falling liquid film, the radial profile curve of liquid slug void fraction in the wake region is also parabolic. Since fully turbulent velocity distribution is built up in the developed region,the void fraction profile in this region is the saddle type. At given superficial liquid velocity, the liquid slug void fraction increases with gas velocity. The radial profiles of liquid slug void fraction at different axial locations are all saddle curves, but void fraction is obviously high around the centerline in the entrance region. The nearer the measuring station is from the entrance, the farther the peak location is away from the wall.展开更多
A generalized corresponding-state model based on two reference fluids was developed for the prediction of surface tensions for non-polar and weakly polar pure fluids and their binary mixtures. Four parameters, p_c, T_...A generalized corresponding-state model based on two reference fluids was developed for the prediction of surface tensions for non-polar and weakly polar pure fluids and their binary mixtures. Four parameters, p_c, T_c, V_c and ω, were used in this model, and the acentric factor ω was used as a scaling parameter. This model has been tested for 69 pure substances and 20 binary mixtures; the average absolute deviations are 0.28 and 0.20 mN/m, respectively. The results indicate that the predictions by means of this model were in good agreement with experimental data. In addition, the calculated deviation would increase with the excess surface tension rising, and if the excess surface tension is less than 3 mN/m, the prediction will be good and credible.展开更多
In this article we consider the fully discrete two-level finite element Galerkin method for the two-dimensional nonstationary incompressible Navier-Stokes equations. This method consists in dealing with the fully disc...In this article we consider the fully discrete two-level finite element Galerkin method for the two-dimensional nonstationary incompressible Navier-Stokes equations. This method consists in dealing with the fully discrete nonlinear Navier-Stokes problem on a coarse mesh with width H and the fully discrete linear generalized Stokes problem on a fine mesh with width h << H. Our results show that if we choose H = O(h^1/2) this method is as the same stability and convergence as the fully discrete standard finite element Galerkin method which needs dealing with the fully discrete nonlinear Navier-Stokes problem on a fine mesh with width h. However, our method is cheaper than the standard fully discrete finite element Galerkin method.展开更多
In this article we consider a two-level finite element Galerkin method using mixed finite elements for the two-dimensional nonstationary incompressible Navier-Stokes equations. The method yields a H^1-optimal velocity...In this article we consider a two-level finite element Galerkin method using mixed finite elements for the two-dimensional nonstationary incompressible Navier-Stokes equations. The method yields a H^1-optimal velocity approximation and a L^2-optimal pressure approximation. The two-level finite element Galerkin method involves solving one small,nonlinear Navier-Stokes problem on the coarse mesh with mesh size H, one linear Stokes problem on the fine mesh with mesh size h <<H. The algorithm we study produces an approximate solution with the optimal, asymptotic in h, accuracy.展开更多
文摘In order to investigate the influence of the entrance effect on the spatial distribution of phases, the experiments on gas-liquid two-phase slug flow in a vertical pipe of 0.03m ID were carried out by using optical probes and an EKTAPRO 1000 high speed motion analyzer. It demonstrates that the radial profile of slug flow void fraction is parabolic. Influenced by the falling liquid film, the radial profile curve of liquid slug void fraction in the wake region is also parabolic. Since fully turbulent velocity distribution is built up in the developed region,the void fraction profile in this region is the saddle type. At given superficial liquid velocity, the liquid slug void fraction increases with gas velocity. The radial profiles of liquid slug void fraction at different axial locations are all saddle curves, but void fraction is obviously high around the centerline in the entrance region. The nearer the measuring station is from the entrance, the farther the peak location is away from the wall.
文摘A generalized corresponding-state model based on two reference fluids was developed for the prediction of surface tensions for non-polar and weakly polar pure fluids and their binary mixtures. Four parameters, p_c, T_c, V_c and ω, were used in this model, and the acentric factor ω was used as a scaling parameter. This model has been tested for 69 pure substances and 20 binary mixtures; the average absolute deviations are 0.28 and 0.20 mN/m, respectively. The results indicate that the predictions by means of this model were in good agreement with experimental data. In addition, the calculated deviation would increase with the excess surface tension rising, and if the excess surface tension is less than 3 mN/m, the prediction will be good and credible.
文摘In this article we consider the fully discrete two-level finite element Galerkin method for the two-dimensional nonstationary incompressible Navier-Stokes equations. This method consists in dealing with the fully discrete nonlinear Navier-Stokes problem on a coarse mesh with width H and the fully discrete linear generalized Stokes problem on a fine mesh with width h << H. Our results show that if we choose H = O(h^1/2) this method is as the same stability and convergence as the fully discrete standard finite element Galerkin method which needs dealing with the fully discrete nonlinear Navier-Stokes problem on a fine mesh with width h. However, our method is cheaper than the standard fully discrete finite element Galerkin method.
文摘In this article we consider a two-level finite element Galerkin method using mixed finite elements for the two-dimensional nonstationary incompressible Navier-Stokes equations. The method yields a H^1-optimal velocity approximation and a L^2-optimal pressure approximation. The two-level finite element Galerkin method involves solving one small,nonlinear Navier-Stokes problem on the coarse mesh with mesh size H, one linear Stokes problem on the fine mesh with mesh size h <<H. The algorithm we study produces an approximate solution with the optimal, asymptotic in h, accuracy.
