Comparison Of Bubble Evolution On Submerged Annular And Circular Nozzles And Study On Submerged Jet Characteristics Of Annular Nozzle

The evolution and dynamic behavior of submerged gas jet experiences two different flow regimes with the increase of gas flow rate: bubble flow regime and jetting flow regime.In this paper,two kinds of flow regimes were analyzed through experimental methods.The bubble formation of annular nozzle and circular nozzle is compared in bubble flow regime.The results show that: in the bubble flow regime,there aren't annular bubble generating from the annular nozzle,nor the bubble formation of the annular nozzle presents the law of bubbling regime which can be divided into three: period-1,period-2 and period-3 like the circular nozzle bubble formation,but the gas jet out from the whole annular nozzle and presents period-3 bubble formation directly,and bubble formation presents a stable circular bubble flow.Before that,the bubble jet out from the random position of the annular and the regime doesn't have a obvious cyclical phenomenon which is called unstable circular flow.The bubble generating from two nozzles have different phenomenon because of the two nozzles: there are two different bubble formation time and bubble formation volume,besides that the contact line radius at the bubble bottom and the puncture phenomenon of two nozzles are different.Pinch-off is an important feature of annular submerged gas jet in the jetting regime,and this dissertation presents quantitative analysis on the judgment of pinch-off.Gas jet presents two stages(continuous jet stage and concentrated pinch-off stage)and the two stages appear intermittently.The influence factors of jet duration time were discussed through the method of experiment date and dimensional analysis,the jet penetration depth are got through the method of image pixel superposition.By observing the experiment images we can know the nature of back-attack phenomenon is that,jet axis is blocked and makes the gas jet by the direction of the horizontal,rather than the gas jet by the contrary direction.As the position of pinch-off isn't certain,so the pinch-off frequency has a distribution at the direction of jet axis,and the frequency gets higher at the farther place away from the nozzle in subsonic condition.