Experimental investigation of the leak hydraulics

Two main issues related to leakage in water distribution systems have been widely discussed in the last decade: the relationship between leak outflow and pipe operating conditions (the leak law) and the effects on the governing equations of the distributed leakage in a pipe. The first issue requires the definition of the relationship between leak outflow and the relevant factors (e.g. the leak area and shape, the pipe material, the head inside the pipe and outside the leak, …). The second issue, i.e. the effect of the leakage on the governing equations of the flow in pressurized pipes, is related to the errors on the estimated parameters, as an example the pipe roughness, due to the numerical calibration of systems with pipes subjected to distributed leaks or distributed demand. It is our belief that this last aspect requires an experimental investigation to correctly define the functional relationships between quantities and the relevant parameters, by considering the flow conditions inside the pipe upstream and downstream the leak as well as the flow through the leak. As a result, an intense experimental activity has been carried out at the Water Engineering Laboratory (WEL) of the University of Perugia. Particularly, the effects of a leak outflow on the momentum equation in a pipe have been investigated.