The paper aims to give a comprehensive investigation of the two dimensional deformation of a single bubble in a straight duct and a 90° bend under the zero gravity condition. For this, the two phase flow lattice ...The paper aims to give a comprehensive investigation of the two dimensional deformation of a single bubble in a straight duct and a 90° bend under the zero gravity condition. For this, the two phase flow lattice Boltzmann equation (LBE) model is used. An averaging scheme of boundary condition implementation has been applied and validated. A generalized deformation benchmark has been introduced. By presenting and analyzing the shape of the bubbles moving through the channels, the effects of the all important nondimensional numbers on the bubble deformation are examined thoroughly. It is seen that by increasing the Weber number the rate of the deformation enhances. Besides, because of the velocity dissimilarity between the particles constructing the bubble, the initial coordinates and the diameter of the bubble play a great role in the future behavior of the bubble. The density ratio has a little effect on the shape of the bubble within the assumed range of the density ratio. Moreover, as the Reynolds number or the viscosity ratio is decreased, higher rate of deformation is exhibited. Finally it is found that there is an inverse proportionality between the amplitude and frequency of the bubble deformation.展开更多
The flow through a rotating U bend duct is investigated by means of visualization. The U bend duct has a cross section of 50 mm×50 mm and a ratio of bend mean radius R c to hydraulic diameter of the duct D of ...The flow through a rotating U bend duct is investigated by means of visualization. The U bend duct has a cross section of 50 mm×50 mm and a ratio of bend mean radius R c to hydraulic diameter of the duct D of 0.65. The rotation axis is parallel with the bend axis. Three cases with rotation number of Ro=-0.2, 0 and 0.2, respectively, are studied at a Reynolds number of 100 000. The results show that the combined effect of rotation and bend curvature strongly influences the flow field, especially in the downstream region of the bend. The evident difference among the flow patterns with different rotation number shows that the secondary flow induced by Coriolis force takes an important role in determining the flow structure.展开更多
文摘The paper aims to give a comprehensive investigation of the two dimensional deformation of a single bubble in a straight duct and a 90° bend under the zero gravity condition. For this, the two phase flow lattice Boltzmann equation (LBE) model is used. An averaging scheme of boundary condition implementation has been applied and validated. A generalized deformation benchmark has been introduced. By presenting and analyzing the shape of the bubbles moving through the channels, the effects of the all important nondimensional numbers on the bubble deformation are examined thoroughly. It is seen that by increasing the Weber number the rate of the deformation enhances. Besides, because of the velocity dissimilarity between the particles constructing the bubble, the initial coordinates and the diameter of the bubble play a great role in the future behavior of the bubble. The density ratio has a little effect on the shape of the bubble within the assumed range of the density ratio. Moreover, as the Reynolds number or the viscosity ratio is decreased, higher rate of deformation is exhibited. Finally it is found that there is an inverse proportionality between the amplitude and frequency of the bubble deformation.
文摘The flow through a rotating U bend duct is investigated by means of visualization. The U bend duct has a cross section of 50 mm×50 mm and a ratio of bend mean radius R c to hydraulic diameter of the duct D of 0.65. The rotation axis is parallel with the bend axis. Three cases with rotation number of Ro=-0.2, 0 and 0.2, respectively, are studied at a Reynolds number of 100 000. The results show that the combined effect of rotation and bend curvature strongly influences the flow field, especially in the downstream region of the bend. The evident difference among the flow patterns with different rotation number shows that the secondary flow induced by Coriolis force takes an important role in determining the flow structure.
