Experimental Study of Air Entrainment from Free Surface in Suction Sump Based on Self-Organised Criticality

Our aim is to understand the air entrainment into a suction pipe inside a suction sump in the vertical-wet-pit-pump configuration. This suction-sump flow accompanying the air entrainment often appears in various industrial and environmental problems, however is usually complicated owing to both its unsteadiness with poor periodicity and its fully-three-dimensionality. In the present study, from a viewpoint of the self-organised criticality (SOC), we conduct long-term measurements with a fine time resolution of 0.1 s using a CdS optical cell. As a result, the air entrainment is classified into two; one with short lifetime and the other with long lifetime. It is suggested that the latter is possibly related with SOC.