液固两相平板混合层中涡结构对颗粒沉降的影响

Influence of vortex structures on particle sedimentation in liquid solid two phase plane mixing layer

为研究液固两相平面混合层中液相大涡结构对固相颗粒运动与沉降的影响 ,分别用粒径小于 40 μm,粒径 98～ 10 4μm以及粒径 15 4～ 160 μm的玻璃微珠作为固相 ,在上下层流体速度比为 1∶ 2的液相平板混合层中 ,用激光片光源显示了在不同高度释放的固相颗粒通过混合层中大涡结构时的沉降扩散过程 ,并与数值模拟结果相对照。随粒径的不同 ,由于液相大涡的作用使颗粒的运动与沉降表现为明显的 3个特征 :在大涡作用下 ,粒径≤ 40 μm的玻璃微珠基本追随大涡运动 ,在实验区不发生沉降 ;粒径 15 4～ 160 μm的玻璃微珠一边随大涡运动 ,一边沉降 ,在实验区域内最终沉降到槽底 ;而粒径 98～ 10 4μm的玻璃微珠既显示出追随大涡运动又显示出穿透大涡的趋势 。

The influence of vortex structures on particle sedimentation in a liquid solid plane mixing layer was measured experimentally. The sedimentation of solid phase particles was visualized as the particles passed through the large vortex structures in a liquid plane mixing layer with a 1∶2 velocity ratio between the upper and lower flow. Glass spheres with three diameter ranges (less than 40μm, 98~104μm and 154~160μm) was used as the solid phase. The flow field was illuminated by a laser sheet. Comparison of the results with a numerical simulation revealed three essential features of particle sedimentation in plane mixing layers. In the large vortex structures, the glass spheres with diameters less than 40μm basically follow the large vortex flow and do not sink . The glass spheres with diameters from 154~160μm normally sink to the floor of the slot. The glass spheres with diameters from 98~104μm follow the large vortex with some settling, so they are an intermediate state.