Explanation for the frequency shift pattern of non-uniform blocked pipeline systems from an energy perspective

Abstract

It was found in a previous study that the transient frequency shifts induced by non-uniform blockages in water pipelines become less evident as the frequency increases, but its physical mechanism is unclear. This paper explains this non-uniform blockage induced frequency shift pattern from an energy perspective. The results indicate that the non-uniform blockages have a less blocking effect on the propagation of high frequency waves; thus, the induced frequency shifts become less evident. In practical applications of non-uniform blockage detection, the frequency of the incident wave should be selected carefully to ensure that the reflected wave contains enough energy.