F151.pdf (4.06 MB)
CCWI2017: F151 'Leakage Modelling: High Leakage Exponents Due to Friction Effects'
journal contributionposted on 2017-09-01, 15:32 authored by Heckmann, Klaus, Sievers, Jürgen
The relationship between pressure and leakage in water distribution systems has been in the focus of several studies. A common description of the pressure-leakage response is a power equation, or a combination of two different powers like in the fixed and variable area discharge (FAVAD) concept. From a theoretical perspective the exponent can be understood as the result of variable leak opening under pressure and the water flow through the leak channel, which may have different behaviour for specific applications. Thus, these theoretical considerations may explain leakage exponents in the range of 0.5 to 1.5 for turbulent flow. This is known to be contradicted by values from field studies, which measure occasionally higher leakage powers. The understanding of this behaviour of leaks is still challenging. In other fields, namely in process industry and nuclear technology, the behaviour of leaks in pipes is also modelled. A relevant ingredient for the leakage-pressure relationship of a crack-like leak in such an installation is the individual flow resistance of a leak. The modelling of such flow resistance, partly due to friction, is the outcome of decades of studies and evaluations of experiments. In the paper, these friction modelling aspects are applied to leaks in water distribution systems. It is shown that the consideration of frictional resistance of leaks can explain leakage exponents higher than 1.5.