Water-Hammer Control in Pressurized-Pipe Flow Using a Branched Polymeric Penstock

This paper investigates the redesigning of existing steel piping hydraulic systems to control severe water hammer positive and negative surges. The applied control strategy is based on adding a branched polymeric short penstock at the transient sensitive regions of the existing system. Two types of polymeric materials used for the short penstock, high-density and low-density polyethylene (HDPE and LDPE), are investigated. The one-dimensional unconventional water-hammer model, based on the Vitkovsky and the Kelvin-Voigt formulations, is used for hydraulic transient analysis, along with the fixed-grid method of characteristics implemented for numerical computations. The numerical model is validated using comparison with experimental measurements available in the literature. The results demonstrate that such a strategy can significantly mitigate the pressure increase and decrease induced by water hammer waves. Moreover, it is found that the short penstock volume and material represent the key factors affecting the damping rate of the positive and negative pressure peaks. The branching strategy used herein induces a smaller increase of the period than does the inline strategy and produces a similar pressure-head damping.