二维平行平板内分散气泡对液相表观黏度影响的数值研究

Numerical study on influence of dispersed bubbles on liquid-phase apparent viscosity in two-dimensional parallel plate

泡状液体广泛存在于各种工业领域,因此深入了解泡状液体的物理特性对产品质量改进和过程强化具有重要意义。本文为了理解气泡对液相表观黏度的影响,揭示液相表观黏度变化的原因,利用流体体积函数(VOF)与动网格结合的方法对二维平行板模型内气泡对液相表观黏度的影响进行了深入的数值研究;分别研究了相同体积分数、不同毛细数工况下,气泡加入对液相表观黏度的影响。结果表明:毛细数和气泡体积分数对液相的表观黏度具有巨大的影响作用;相同的体积分数下,当毛细数较大(Ca>1)时,气泡的加入会使液相的相对黏度减小,体积分数越大,液相的相对黏度减小得越严重;另外,相同的体积分数下,当毛细数较小(Ca<1)时,气泡的加入会使液相的相对黏度增大,体积分数越高,液相的相对黏度增大得越明显。

Bubble liquid exists widely in various industrial fields,so the detailed understanding of physical properties of bubbly liquid is of great significance for improving the quality of products and for strengthening industrial processes. In this paper,in order to understand the influence of bubbles on the liquid-phase apparent viscosity and to explain the changing reason of the liquid-phase apparent viscosity, based on two-dimensional parallel plate model, the effect of large bubbles on the liquid-phase apparent viscosity was deeply investigated with the volume of fluid（VOF） method combined with the dynamic mesh. The effect of bubbles on the liquid-phase apparent viscosity was numerically studied in detail under the conditions with the same void fraction but different capillary numbers. The present study showed that the capillary number and the bubble volume fraction has the great effect on liquid-phase apparent viscosity. For the same volume fraction,when the capillary number is relatively large（Ca1）,the bubble injection causes the decrease of the relative viscosity of the liquid phase,and the larger the volume fraction is. The relative viscosity of the liquid phase decreases more sharper. In addition,under the same volume fraction,when the capillary number is relatively small（Ca1）,the relative viscosity of the liquid phase increases due to the addition of bubbles,and the higher the volume fraction is. The relative viscosity of the liquid phase increases more obviously.