Experimental study on the inuence of the incline angle of narrow-necked container on bottleneck effect

Periodical oscillatory flow typically occurs at bottleneck when liquid is poured out of a narrow-necked container. This unsteady flow phenomenon is defined as Bottleneck effect. In this experimental study, a synthetic glass container with adjustable incline angle, rotation speed, bottleneck sizes and location of rotation axis was designed. A high speed camera was employed to record the flow phenomena of bottleneck effect. The fundamental of bottleneck Effect was investigated, and the inuence of incline angle on bubble generating, growing and the average ow rate were carefully studied. The result shows that bottleneck effect occurs only when the incline angle is no less than a critical angle which is 86° in this experiment. As the incline angle increases, the stability of bubbles decreases during the process of generation, coalescence and breakup, furthermore, the average flow rate goes up in the beginning and then drops down. In this experiment, the inclination angle for the maximum average flow rate of pouring water was 160°.