Abstract:

ESDU 89030 introduces a program, ESDUpac A8930, that predicts, following pump trip and/or valve operation, the changing values at a junction of liquid pressure and flow velocity, structural displacement, velocity and acceleration, and piping forces in a liquid-filled planar system. The effect of the mutual coupling of the fluid and pipe behaviour is included in the analysis (or, if desired, can be neglected). Guidance is included on modelling the pump characteristics and the valve closure/time behaviour. Values of friction factor and wave speed are required for each pipe, or can be computed by the program. Data on the natural vibration characteristics of the system are also necessary, and can be generated by ESDU 88022, in which case they will be in the format required by the program. The effects of axial strain in the pipe walls are neglected, and the program assumes elastic structural behaviour and a homogeneous fluid. Thus, although gas release and cavitation are predicted, their subsequent effect on the system behaviour cannot be modelled. Steady-state values of pressure, flow velocity, structural displacement and piping forces are calculated before the transient analysis. A detailed explanation of the input data and their format is given, together with a worked example illustrating the use of the program and the presentation of the output. Graphs produced from the program show a comparison between a coupled and uncoupled calculation of the structural parameters and fluid pressure at two points in the system.