Study On Motion Behavior Of Single Bubbles In Yield-Stress Fluid

In this paper,the formation,rise and mass transfer of bubbles in the yield stress fluid were studied.The shape and velocity of bubbles in the yield stress fluid and the flow field and concentration field around the bubble were obtained by experiments and numerical simulations.The rising process,the bubble shape,the trajectory of the bubble,the flow field and the concentration field of the surrounding liquid phase are discussed.The mechanism of the bubble movement affected by the flow field structure around the bubble,the local viscosity of the fluid and the yield stress is analyzed.The main contents of this paper include:Bubble formation test: The same flow rate,Capobol solution and deionized water bubbles in the size and shape of the similarities and differences are compared.In the capobol solution bubble volume growth rate is faster than in deionized water.The aspect ratio of the bubbles in capobol solution is basically the same in the range of 100 ms to 150 ms,and the aspect ratio of the bubbles in the capobol solution is higher than in the deionized water in the initial and final stages of bubble generation.Bubble rising trajectory experiments: The trajectories of different sizes of bubbles at different concentrations were studied.The results show that when the Reynolds number of bubbles is small,the bubbles rise linearly in deionized water and capobol solution.When the Reynolds number increases to the critical value,the bubbles begin to spiral in a certain amplitude and rise in a "Z" shape in the two-dimensional image.The magnitude of the oscillation amplitude is related to the equivalent radius of the bubble and the nature of the fluid,Reynolds number is related.So in the critical range of bubbles in the initial stage rise straight line up when the speed reaches the critical value and then began to spiral.Study of Bubble Shape and mass transfer: The main shapes of bubbles in capobol solution including spherical shape,ellipsoidal shape and teardrop shape.Bubbles' shape were made according to two dimensionless numbers.Finally,a correlation between the bubble aspect ratio and the self-defined dimensionless Wy and the error range predicted by this formula is given.