Experimental and numerical studies on movement of air in water pipelines

This report is the second output on research into air problems in pipelines and follows a comprehensive literature review (Lauchlan et al, 2004). It describes experimental and numerical studies that were conducted to enable the development of design guidance on how to minimise the negative effects of the presence of air pockets in pipes, particularly for mild slopes. The report describes the design of a test facility, its operation, tests carried out and the development of design formulae on critical flow velocity for air pocket movement and on the rate of expulsion of air through hydraulic jumps. Findings are also described on air pocket velocity, bubble velocity downstream of hydraulic jumps and on other characteristics associated with hydraulic jumps, and on the effect of air pockets on the hydraulic gradient. The tests were carried out in a 150mm internal diameter pipe at slopes varying between 0 and 22.5 degrees but, in view of past research findings, the present results can be taken as generally valid for slopes up to about 40 degrees.