气泡在液池中生成及上升行为特性研究

Experimental Study on the Characteristics of Bubble Generation and Rising Behavior in a Liquid Pool

摘要: 本文采用格子Boltzmann方法研究在气泡生成和脱离阶段，入口速度和管口管径的变化对气泡性质变化的影响以及在气泡上升阶段，Eötvös数(Eo)的大小，对气泡界面以及速度变化的影响。我们发现对于不同入口速度，气泡完全脱离时刻的形态有明显差异：当V = 0.02 m/s时，气泡形态呈扁平状，当V = 0.05 m/s时，气泡形态呈椭球状，而当V = 0.1 m/s和V = 0.2 m/s时，气泡形态呈近似球状。其次，随着入口速度的增大，气泡完全脱离时刻的体积越大，从生成到脱离所需要的时间越短。对于不同管口管径，气泡完全脱离时刻的形态也有明显差异：当管径d = 0.004时，气泡脱离时刻呈水滴状，当管径d = 0.005和d = 0.006时，气泡呈近似球状，当管径d = 0.07时，气泡呈椭球状。结果表明，随着管口管径的增大，气泡完全脱离时刻的体积越大，从生成到脱离所需要的时间越短。在气泡上升阶段，我们主要研究Eo对气泡界面以及速度变化的影响：当Eo = 10时，气泡从球状变为半球状；当Eo = 50时，气泡从球状变为月牙状；当Eo = 100时，气泡运动至顶端时会产生拖尾；当Eo = 200时，气泡最终呈头盔状。在不同Eo数下，气泡质心速度均随气泡上升高度的提高而增大，且上升高度处于125至450区间时趋于稳定。气泡终端速度随Eo增大而增大，且小Eo对气泡终端速度的影响更加明显，随Eo增大，气泡终端速度的变化越来越小。

Abstract: In this paper, lattice Boltzmann method is used to study the influence of inlet velocity and orifice diameter changes on bubble characteristics during bubble generation and detachments stages, and the influence of Eotvos number (Eo) on bubble interface and velocity changes during bubble rising process. It is found that the shape of bubbles at the moment of complete detachment varies significantly depending on the inlet velocity: the bubble shape is flat at V = 0.02 m/s, elliptical at V = 0.05 m/s, and roughly spherical at V = 0.1 m/s and V = 0.2 m/s. On the other hand, the bubble’s volume at the point of full detachment increases with increasing inflow velocity, resulting in a shorter time between generation and detachment. There are notable variations in the shape of bubbles at the point of complete detachment for different pipe diameters: the bubble shape at detachment time is a water droplet when the pipe diameter is d = 0.004, it appears roughly spherical when the pipe diameters are d = 0.005 and d = 0.006, and it appears ellipsoidal when the pipe diameter is d = 0.07. The findings show that the volume at which the bubbles fully detach increases with pipe diameter, and that the time needed from production to detachment decreases. During the rising phase of the bubbles, the influence of Eo on bubble dynamics and velocity variations are mainly investigated. When Eo = 10, the bubble changes from spherical to hemispherical. When Eo = 50, the bubble changes from a sphere to a crescent. When Eo = 100, the bubble moves to the top with a trailing tail. When Eo = 200, the bubble ends up in the shape of a helmet. Under different Eo numbers, the bubble centroid velocity increases with the rising height of the bubble, and tends to be stable when the rising height is between 125 and 450. The bubble terminal velocity increases with the increase of Eo, and the effect of small Eo on the bubble terminal velocity is more obvious. With the increase of Eo, the change of the bubble terminal velocity becomes smaller and smaller.