Author(s): Arris S. Tijsseling, Alan E. Vardy
Linked Author(s): Arris Tijsseling
Keywords: Water hammer, pressure surges, fluid transients
Abstract: The influence of boundary conditions on water hammer in a traditional reservoir-pipeline-valve system is studied. At first sight this seems a trivial matter. However, a second look reveals some surprising aspects not known to many and therefore presented herein. Water hammer consists of transient pressures P and transient velocities V, the histories of which are largely determined by sonic speed c, pipeline length L, liquid density ?, initial flow velocity V0, and effective valve closure time ?. The last parameter is zero herein, because, for clarity, we consider instantaneous valve closures in frictionless pipelines. The questions raised and discussed in this paper are: i) 4L/c versus 2L/c systems, and do 3L/c systems exist?; ii) is an orifice an open end or a closed end, or neither of these?; iii) can all the hydraulic system's resonance frequencies be found from a measured water-hammer history?; iv) can measured pressures reliably be used as boundary conditions?; v) why can we have two boundary conditions at one end in the frequency domain, and not so in the time domain?; vi) are wave speed and phase velocity the same thing?; vii) is my valve structurally fixed? Things are explained from basic principles and simple test cases
Year: 2017