Study of aircore phenomenon and influence of water height during liquid draining

Draining of liquids through cylindrical tanks is a very common phenomenon and has many applications. Understanding the aircore formation and its growth during draining has attracted appreciable interest in the literature. In this study, water draining through cylindrical tanks was studied using experimental and numerical techniques. Eight different initial heights of water in the tank between 310 and 450 mm with a 20-mm increment were tested in each experiment. The numerical study shows good agreement with the experimental data and promotes understanding of the generation and disappearance of an aircore during draining. For the different initial water heights, the experiments were performed with and without initial rotation of the tank. It is found that in the experiments without initial tank rotation, the drain time of water increases with increasing initial height. On the other hand, the drain time remains almost the same for all initial heights tested with initial tank rotation. The small variation in the drain time even when the initial water level is reduced is explained by the aircore duration during draining. Also, the mechanism of generation and disappearance of aircore is proposed with the help of numerical results.