| Bubble movement is widely found in industrial production,such as the phenomenon of cavitation of oil and water separator,jet erosion of ship propeller,boiler boiling and submarine operation discharge exhaust gas.In this paper,underwater exhaust bubble as the research object,to explore the underwater single bubble motion characteristics,underwater bubble generation mechanism,bubble volume changes and bubble material composition(such as carbon dioxide)and the bubble group bubble Gather together.Firstly,the single-bubble model is established based on Newton's law,and the stress state of the bubble in the variable fluid is analyzed.The change of the bubble size,the size of the acceleration and the bubble generation volume are studied.Secondly,the simulation model of underwater bubble is established by numerical simulation method,and the mechanism of bubble generation and the change of its trajectory are discussed.The size of the bubble volume was calculated by the combination of the multiphase flow VOF and the Level Set,and the relationship between the bubble volume and the bubble outlet pore diameter,the average flow rate of the exhaust gas and the dissolution characteristics(due to the different bubble components)was studied.The results show that the bubble volume generation process can be divided into "expansion phase" and detachment stage.When the bubble outlet pore diameter is constant,the gas flow rate increases,the bubble volume increases and the separation time becomes shorter.Based on the Maxwell-Stefan equation,when the bubble solubility is discussed,it is found that the carbon dioxide solubility during the bubble motion is small and can be neglected at room temperature.Based on Fluent's UDF programming,the fragmentation and aggregation of bubbles in the bubble group were studied.The results show that the bubble breakage and aggregation phenomenon are not obvious when the bubble group starts to move.When the bubble moves for some distance,The randomness of the phenomenon is more and more frequent.At the same time,the bubble diameter distribution of the bubble group was obtained by the population equilibrium model,and it was found that the bubble diameter became V-type distribution,and the whole bubble diameter increased with the height of the motion.Finally,in order to verify the correctness of the calculated model,the underwater bubble kinematic characteristic test is carried out.Taking into account the serious attenuation of underwater light,in order to adapt to complex and volatile underwater environment,the rational design of the corresponding underwater lighting system.Note that the blue light penetration ability,light loss is small,select the blue LED lights for the lighting source.Because of the influence of suspended particles and water body on the absorption and scattering of light energy,the bubble image acquisition is more demanding on the performance of high-speed cameras.The COMS industrial camera is used to build the bubble image acquisition platform.The results are basically the same: After the first linear motion spiral rise,the bubble horizontal direction gradually increased,reaching the surface after the speed close to zero.The motion of the bubble group is complex and changeable,and the bubble particle size distribution conforms to the population equilibrium model. |
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