Author(s): Carlos Cruickshank Villanueva
Linked Author(s):
Keywords: Pipe crossings; Vorticity at bends; Mass exchange; Pipe networks
Abstract: Results from previously published (XXI Hydraulics Latin American Congress, 2004) laboratory experiences and their analysis contradict the hypothesis of full mixing of inflows at pipe crossings of pipe networks. The experiments showed that the crossing is not a place where the inflows mix but rather where they reject each other. This is because they deflect as in a bend and the secondary currents create self preserving vortices. This was observed for crossing angles from 42° to 135°. Partial mixing occurs when one inflow is larger than the other. Concentration measurements from the mentioned experiments are reanalysed and a criterion is established to compute the mass exchange of the two inflowing currents at a crossing and to compute the outflow concentrations of a dissolved substance when one knows the inflow concentrations and the flows. The established criterion is applied to two hypothetical water distribution networks to illustrate the errors to which the full mixing hypothesis leads. These errors consist in flattening the concentration distribution in the network.
Year: 2007