重力水平与粘度变化对水平槽道泡状湍流影响的数值研究

Numerical Simulation of Gravity Level and Viscosity Change's Influence on the Bubbly Turbulence in Horizontal Channel

鉴于泡状流在工业及太空领域均具有广泛的应用前景,综合研究重力及黏度变化对液相湍流的影响是必不可少的。文中采用数值模拟方法,分别研究了气泡加入后重力水平和黏度变化对液相湍流统计量和气相体积分数的影响。结果表明:在常重力下,气泡注入后湍流强度与雷诺应力被调制,绝大部分大部分气泡聚集在上壁面;而在无重力下,液相的湍流强度及雷诺应力基本不变,气泡均匀分布在槽道内。黏度对液相湍流的影响与重力相类似,不同的是无论黏度改变与否,绝大部分气泡均聚集在上壁面处。且气泡加入后重力水平及黏度变化对液相湍流的影响是由气泡对湍流的调制作用和局部黏度变化共同作用的结果。

Bubbly flow has a wide application prospect in the fields of both industry and space, so it＇s essential to perform detailed studies the on influences of gravity level and liquid phase viscosity change on liquid turbulence. In this paper, the influences of gravity level and viscosity change on the liquid turbulence sta- tistics and the gas phase volume fraction were investigated with numerical simulation method. The present results show that, under the normal gravity, the liquid turbulence intensity and Reynolds stress were mod- ulated due to the microbubble injection, and most of the microbubbles gathered near the upper wall. How- ever, under the zero gravity, the liquid turbulence intensity and Reynolds stress almost keep unchanged, and bubbles evenly distributed in a whole horizontal channel. The influences of viscosity and gravity on the turbulence intensity are similar, and the difference is that most of the bubbles are gathered near the upper wall regardless of the viscosity change or not. The studies also show that the influence of gravity level and viscosity change on the liquid turbulence is an emergent property resulting from turbulence modulation and local viscosity change.