氨气气泡在水中的上升和传质特性OA

The rising and mass transfer process of ammonia gas bubbles in water were numerically simulated using VOF(volume of fluid)method and penetration theory model,and the simulation results were experimentally verified.The effects of the initial diameter of the bubbles on the velocity,wake,mass transfer trails and coefficients during their rising process were investigated.The results show that the mass transfer process has a significant impact on the rising process of ammonia gas bubbles.During the rising process,the larger the initial diameter of the bubble,the smaller the transverse velocity fluctuations and the larger the longitudinal velocity fluctuations.The mass transfer process causes the bubble wake undergo an earlier transition from a symmetric state to a transition state,and finally to an asymmetric periodic shedding state.As the initial diameter increases,the length and width of the bubble wake increase,and the asymmetry of the wake vortex increase.The wake structure has a greater impact on the mass transfer of the smaller bubbles.The initial bubble mass transfer trails show obvious axisymmetric features,and with time,the bubble mass transfer trails become more and more irregular under the effect of wake flow and diffusion.The larger the initial diameter,the smaller the mass transfer coefficient during the rising of the bubble.