Numerical Investigation Of Bubble Behavior

Cavity and buoyancy driven bubbles often occur in nature and industrial produc-tion processes. The numerical investigation of their behavior is of both academic and practical application values. In this paper a VOF method for an axisymmetric flow is improved, where an incompressible flow of two fluids with different viscosities and densities is treated as an incompressible flow of single fluid with variable viscosity and density. Within the inviscid and incompressible flow frame and by neglecting surface tension effects the behavior of an axisymmetric bubble or drop rising or falling in an-other fluid is simulated, the generation mechanism of the liquid jet and the mechanism of the effects of the density ratio of the two fluids on the deformation of the bubble or drop are analyzed. Within the inviscid and incompressible flow frame the behavior of an axisymmetrically rising bubble driven by buoyancy is simulated, the mechanism of surface tension effects on the behavior of the bubble is analyzed, and 4 critical Weber numbers are found, which distinguish the different behaviors of the bubble. Within the incompressible flow frame and by neglecting surface tension effects the behavior of an axisymmetrically rising bubble driven by buoyancy is simulated, the mechanism of viscosity effects on the behavior of the bubble is analyzed, and 3 critical Reynolds numbers are found, which distinguish the different behaviors of the bubble. Within the inviscid and incompressible flow frame and by neglecting surface tension effects the behavior of two axisymmetrically rising bubbles driven by buoyancy is simulated, the mechanism of the effects of their relative sizes and the relative distance on their behavior is analyzed, and some critical values of the relative distance are found, which distinguish the different behaviors of the bubbles. Within the inviscid and incompress-ible flow frame the behavior of two axisymmetrically rising bubbles with same size and different relative distances, which are driven by buoyancy, is simulated, the mecha-nism of surface tension effects on the behavior of the bubbles is analyzed, and 4 critical Weber numbers are found, which distinguish the different behaviors of the bubbles. Within the incompressible flow frame and by neglecting surface tension effects the behavior of two axisymmetrically rising bubbles with same size and different relative distances, which are driven by buoyancy, is simulated, the mechanism of viscosity ef- fects on the behavior of the bubbles is analyzed, and 3 critical Reynolds numbers are found, which distinguish the different behaviors of the bubbles. Within the inviscid and incompressible flow frame and by neglecting surface tension effects the behavior of an axisymmetrically rising bubble near a free surface, which is driven by buoyancy, is simulated, the mechanism of the generation and development of the liquid column during and after the burst of the bubble and the mechanism of the effects of the rela-tive distance between the bubble and the free surface on the behavior of the bubble are analyzed, and a critical value of the relative distance on the behavior of the bubble is found, which distinguishes the different behaviors of the bubble. Within the inviscid and incompressible flow frame the behavior of an axisymmetrically rising bubble near a free surface in different relative distances between the bubble and the free surface, which is driven by buoyancy, is simulated, the mechanism of surface tension effects on the behavior of the bubble is analyzed, and 2 critical Weber numbers are found, which distinguish the different behaviors of the bubble. Finally, in the single grid system with uniform grids a VOF method for simulating the behavior of a cavity near a rigid wall is developed, which is based on the liquid flow outside the cavity and only considers the dependence of the gas pressure inside the cavity on the cavity volume.