Column separation and rejoinder during rapid pipeline filling induced by a partial flow blockage

ABSTRACT A new mechanism for inducing column separation and rejoinder during rapid filling of gravity pipe systems is numerically and conceptually identified. A shock-fitting model is combined with the discrete gas cavity model to compute the resulting water hammer due to column rejoinder. Numerical explorations show that column separation may be induced during rapid filling when the water column encounters a flow restriction such as a partially open valve followed by a “V-shaped” pipe profile. Interestingly, the resulting pressure spikes are sometimes capable of inducing a new or secondary column separation event near the front of the advancing water column front, an event associated with the sudden jump in velocity carried by the propagating rejoinder shock wave. A physical interpretation of the captured events is provided and model results are shown to compare favourably to a previously published set of experimental data involving column separation and rejoinder.