Hydraulic Performance of Penstock Trifurcations

The pressure distributions and the energy losses were obtained in an air tunnel for the following penstock trifurcations: a two-wye arrangement, two types of plug-funnel proposal, and an abrupt junction. Published results of other types of trifurcation, namely, the one provided with a tie bar, and other wyes have been also included in this report in order to provide a comprehensive aid for the designing engineer in selecting the right type of trifurcation. The model tests were made for all the three operating conditions: one branch flowing, two branches flowing and all three branches flowing. It is found that the energy-loss coefficient depends only on fluid inertia for approach, flow Reynolds numbers greater than 10⁵. The plug-funnel trifurcation in which the central portion is recessed was found to be hydraulically better than the other models tested when all the three branches are flowing because the boundary geometry provides a smooth entry into all three branches. The double wye is, however, superior to all other types when only one branch is flowing.