On air-entraining flow in pump's sump with a vertical suction pipe below critical submergence

Abstract

In pump’s sumps, the air entrainment sometimes occurs. Such flow accompanying the air entrainment becomes complicated owing to both of its unsteadiness with poor periodicity and its fully-three-dimensionality. In various industrial and environmental problems, the air entrainment often induces vibration, noise, low pumping efficiency or pump’s collapse at the worst, and is usually complicated owing to both their unsteadiness with poor periodicity and their fully-three-dimensionality. The present aim is to understand the air entrainment into a suction pipe, which appears inside a simple and basic suction sump in the vertical-wet-pit-pump configuration. In particular, we focus upon the influences of governing parameters upon the occurrence-time ratio γ of the air entrainment in over-critical-submergence condition, using a conductance-type electric sensor which can detect the existence of air bubbles through a suction pipe with no disturbances by the sensor probe and with a fine spatial resolution in order to achieve accurate measurements. As a result, we reveal the influences of such three kinetic parameters as the Froude number, the Reynolds number and the Weber number (or the Bond number) together with four geometric parameters upon the air entrainment and the free-surface pattern inside the suction sump.

Keywords

• pump
• suction sump
• open sump
• water intake
• three-dimensional flow
• two-phase flow
• unsteady flow
• air entrainment