Eccentric drain port to prevent vortexing during draining from cylindrical tanks

A vortex with an air core forms during draining of the liquid from a circular tank through an axisymmetrically placed circular orifice as the free surface level reaches a critical height of the liquid (H_c). The vortex extends to the bottom port, reducing the effective cross-sectional area of the drain outlet and the flow rate. Attempts have been made to suppress vortexing using different methods. The study that showed vortexing can be prevented by using eccentric drain holes, even with initial rotation given to a liquid column, has been presented. The study is carried out with different values of eccentricity parameter e/R. The results of this study showed that vortexing during draining from a cylindrical tank can be prevented by providing an eccentric drain port, in which case the eccentricity has to be equal to or higher than 0.4. The disadvantage appears to be that the draining time without rotation for eccentric ports is about 18% higher than that for the axially located ports.