WATER-HAMMER WITH FLASHING IN A PIPE

A problem of water hammer caused by sudden valve closure is calculated by the method of characteristics. A fluid flow is described by system of conservative equations (continuity, momentum and energy) which wer e reduced to one dimension problem. Friction forces and heat transfer terms were neglected. The system is transferred to the characteristic form and solved numerically. The developed method is used for calculat ion of a simple system of a horizontal pipe where fluid flows with con stant velocity v(0). The constant pressure po is maintained on the sid e of the pipe connected to the tank. On the other side is a valve whic h is closed in Me moment. A strong pressure pulse appears and expands over the hydraulic system. If the velocity v(0) is high enough the pre ssure at the valve during transient falls bellow the saturation point (p(min) < p(S)). A phase transition and two-phase flow appears what ma y result in much larger pulses. The results of the calculations ore co mpared to the experiment done at Michigan University [1].