LIFT FORCE OF LARGE BUBBLE IN HIGH REYNOLDS CONDITION

摘要

In the present study the lift force of an air bubble in water was measured in the shear flow condition. The linear shear flow were developed using a large L-shaped channel in which the water fluid elements accelerated differently from inner edge to the outer edge. The linearity of flow was empowered by vanes with different distances. The present lift force test rig is more realistic in terms of the medium and Reynolds number than previous experimental works in which smaller test section and viscosity tuned medium were employed. Due to the large scale of the system, the data were harnessed for the relatively large bubbles which were suspected that lift coefficients were changing from positive to negative. We have observed that the moving characteristics such as spiral or zigzag affect lift force very much. For large bubbles data were scattered but bubble with zigzag motion always were subjected by large negative lift force but bubbles with spiral motion were subjected by the negative lift force with almost constant lift force coefficient. The present lift force data showed almost same trends with the model of Tomiyama et al. but larger than it in many cases so further study is called to improve its accuracy.