Background Pressure Characterization in Pipeline Systems and THE RAYLEIGH DISTRIBUTION

This paper aims to study the characteristics of background pressure fluctuations in water supply systems. Pressure fluctuations are measured with high frequency transducers in: (i) water pipeline lab facility in the Hong Kong University of Science and Technology; and (ii) a real water distribution system in a residential area in Ngau Tau Kok, Kowloon, Hong Kong. The pressure fluctuation amplitudes are found to follow the Rayleigh distribution for both lab and field data. In the lab, the agreement between the data and the distribution improves as Reynolds number increases, hinting that turbulence is a possible cause of such distribution. The classical -5/3 spectral slope for turbulence is also observed. Parameter estimation of the -stable distribution has also been conducted. The measured pressure data are found to have a heavy-tailed and skewed distribution compared to the Gaussian distribution. Spectral peaks corresponding to the resonant frequencies of transients in a reservoir-pipe-valve system is observed for Re<25000. For field measurements, the histograms show a “heavy-tail” compared to the Rayleigh distribution.