Drainage of liquid from a small circular hole in a vertical wall

In this work, the initiation and cessation of flow from a hole in a vertical wall was examined. Water, ethylene glycol or isopropyl alcohol was slowly added to polypropylene (PP) or fluorinated ethylene propylene (FEP) containers with a single circular hole in their side wall. If the hole was sufficiently small, liquid rose past the hole. No liquid flowed through the hole until a critical height was reached. Flow generally ceased before the level of the liquid reached the bottom of the hole. The onset and cessation of flow was successfully modeled as a balance between the hydrostatic pressure in the bulk liquid and the Laplace pressure of the air-liquid interface bulging from the hole.