生物转盘表面液膜流动特性数值模拟

采用计算流体动力学(CFD)方法,运用流体体积(VOF)模型研究生物转盘表面液膜流动特性,分析了传统实心转盘和新型开窗转盘表面液膜的成膜特性、厚度和速率等,并考察了不同转盘厚度对成膜和液膜厚度的影响。结果表明:实心转盘的液膜自上而下平缓过渡,而开窗转盘中,开窗区域附近出现液膜位置的急剧变化,并在槽内液体下方发现很多不规则的气泡;转盘在上升区的液膜厚度随角度的增加快速减小,而下降区的液膜厚度基本不变,趋于稳定;转盘开窗形成的自由膜速率大,更新频率快;在研究范围内,不同厚度转盘形成的液膜随转盘厚度增加,开窗区域的自由膜厚度增加。

Numerical Simulation of Flow Characteristics of Surface Film in Rotary Biological Contactor

The film flow characteristics on surface of rotary biological contactor (RBC) were numerically simulated using Computational Fluid Dynamics (CFD) method and thevolume of fluid (VOF) model. The pattern of liquid film formation, film thickness and velocity distribution on the solid disc and window disc were investigated, respectively. The effects of the disc thickness on the pattern of liquid film formation and film thickness were also investigated. The results showed that the liquid film transited smoothly on the solid disc while the liquid film on the window disc dramatically changed in the location near the window area, and many irregular bubbles were found in the tank below the liquid. The film thickness decreased rapidly with the increase of the angle in the rising zone but kept unchanged in the dropping zone. The velocity of free film and its update frequency on the window disc were faster than those of wall-bound film. Within the scope of this research, the thickness of free film on the window disc increased with the increase of the thickness of disc.