Experimental and analytical study of the air-water Interface kinematics during filling and emptying of a horizontal pipeline

Abstract

It is demonstrated that the air-water interface in a large-scale pipeline during Its filling and emptying reveals different kinematical conditions In addition to shear at the pipe wall, there is also shear produced by air Intrusion inside the water colunin The experimental findings of unidirectionally moving water fronts along the horizontal test section of a PVC pipeline with diameter-to-length ratIo 11100 are analysed A simple Control Volume model is used for modelling of the water-front splitting in the pipeline, where free-surface and mixed stratified flows are present. The Froude-number criterion is used to figure out the hydraulic regimes (sub- and supercritical) of the stratified flows in the pipeline The Zukoski dimensionless number, which characterizes the relative shortening of the water column due to air intrusion on top of the moving water column, is also estimated