Motion Characteristics Analysis And Drag Model Correction Of Single Bubble Movement

A large quantity of bubbles exist in a gas-liquid two-phase system. As the basic problems of gas-liquid two-phase system study, the laws of generation, growth and movement of bubbles provide the basis of design, manufacture, application and maintain for relational equipments. The stress state of a bubble in the movement process is complex and uncertain, while the influence of the drag remains being. With increasing focus on the study of the drag model, a series of achievements have been obtained. While the most study was on the bubble in uniform motion, and the general drag coefficient model has not been achieved without enough consideration to the affecting factors. According to the problems and deficiency, the following respects were studied in this thesis.Experiment system was set up with the OLYMPUS i-SPEED3 fast-action camera as the key equipment. The generation and movement process of stainless steel pinhead with different size was recorded with the experiment system, respectively. Through which the tracks, sharp variations and dynamic information(velocity and acceleration) were obtained. The data achieved were analyzed with Image-Pro Plus7.0. For more convenient analysis, the motion process are divided into uniform speed stage(USS) and acceleration stage(AS). And the motion characteristic in these two stages was studied, respectively.The stress state in the motion process of bubble was studied. Based on the experimental data, the theoretical drag coefficient model of the USS and AS was established, respectively. The calculation formula was obtained through the dimensionless analysis based on Buckingham P theorem. On the basis the relation of deformation coefficient and dimensionless parameters was confirmed with least square method. Through which the classic drag model was amended. The comparison between with the experimental data and the classic model verified the accuracy and reliability of the amended model.The flow field around, the motion and deformation law of the single bubble motion in still water were analyzed with PIV method. When the single bubble moves in the ionic water, the maximal velocity of the fluid behave above and beneath the bubble, the fluid around move downward and the velocity of which decrease with the increase of the distance. With a large diameter, the bubble moves in zigzag, and the larger diameter is accompanied by larger deformation. Under the shear force the vortex generates, and falls off at the inflection point of the zigzag path. With a smaller diameter, the trace of the movement tends to straight line, and the large velocities appear above and beneath the bubble in the flow field, which decrease with the increase of the distance.In this thesis, the motion characteristics and the flow field around are analyzed, the drag coefficient model are established with more exhaustive consideration of affecting factors. Which results in the applicability of the drag model spreading, and referential basis may provided for theory research and engineering application.