Reservoir Influence on Pressure Wave Propagation in Steel Pipes

The relation between the length of steel pipe and the pressure wave period in the system, reservoir-pipe-valve, is discussed. Experiments carried out for the short steel pipes showed that in such a system, the pressure wave celerity estimated using the measured wave cycles systematically increases with the increase of the pipe length. The observed differences can exceed even $90\mathrm{m}/\mathrm{s}$. As the pressure wave traveling in the pipe with a speed dependent on the pipe and fluid properties is reflected from the reservoir, one can expect that this process is not as ideal as it is assumed, but it needs some time to happen. This causes a wave cycle to increase so that an apparent wave celerity occurs. For determination of the real value of the wave celerity, a modified laboratory installation was designed. This facility is constituted by a pipe closed at its both ends and divided into two parts by the third valve installed midlength. Water in both parts of the pipe is subjected to different hydrostatic pressure so that the unsteady flow is generated by the discontinuous initial condition. The experiments carried out using this installation allowed determination of the real value of pressure wave celerity for the considered steel pipeline and relation with the one occurring in a reservoir-pipe system. Based on the acquired experimental data, an approach to estimate the time of pressure wave reflection delay in a reservoir is proposed.