Abstract. Several transport mechanisms govern the cross-sectional particle distribution in fully developed turbulent flow in a pipe. These transport mechanisms affect particle load deposition as well as particle resuspension, which are identified as principal protagonists in the build-up of potential discolouration risk in drinking water distribution systems (DWDS). Both are to a large degree controlled by particle size and flow conditions. However, so far, these relationships are not completely understood in the context of DWDS.

In this research we have attempted to identify under which conditions particles suspended in water are transported towards the pipe wall, which generate favourable conditions for deposition. Experimental results are reported and then compared, qualitatively and quantitatively, to the theoretical predictions in the regime transport map for turbulent flow proposed by van Thienen et al. (2011a). The research was conducted by completing a series of experiments in a laboratory test facility with different hydraulic regimes and different particle size ranges. A newly developed optical tomography measurement system was used in order to produce cross-sectional images of particle concentration in water flowing inside a pipe. The experimental results allowed us to identify flow conditions and particles sizes under which gravitational settling and turbophoresis dominated the radial particle transport. These findings show a good correspondence between experimental data and theoretical predictions on the occurrence of turbophoresis and lead to a better understanding of the processes that increase the potential discolouration risk in DWDS.