Experimental Investigation on Bubbly Flow in Rectangular Channel Under Rolling Condition

Experimental study of rolling effects on characteristics of bubbly flow in a rectangular duct (43 mm×3.25 mm×2000 mm) was performed under ambient temperature and pressure. The characteristics of bubbly flow in vertical, inclined and rolling channels have been obtained through visualization and photographic recording. In the experiment, the gas and liquid superficial velocities ranged from 0.07 m/s to 0.15 m/s and from 1.6 m/s to 2.39 m/s respectively. The bubble clusters contained no less than two bubbles exist in vertical, inclined and rolling channels. With the inclined and rolling angle increase, the bubble clusters tend to contain more bubbles. In vertical case, most bubbles aggregate in the intervals near the narrow wall, thus forms high number fraction peaks at the position around 2x/w = ±0.5. As the inclination and rolling angle increase, the bubble number fraction near the lower wall decreases and that near the upper wall increases. In addition, the number fraction peak close to the lower wall disappears and that near the upper wall becomes higher and sharper at the inclined and rolling angle no less than 10°. There exist no significant differences in bubble lateral distribution under inclined and rolling conditions at the same angle. To identify the influence of rolling on bubble lateral distribution, comparison between lateral buoyancy and additional buoyancy is made theoretically. The results show that the influence of additional buoyancy on lateral bubble distribution can be neglected result from the magnitude of lateral buoyancy is much larger than that of additional buoyancy.