| Transient pressure in piped liquid is a function of structural restraint at an elbow. When supported rigidly, the elbow causes no appreciable alteration of the pressure transient generated by rapid valve closure. However, if the support is relaxed, significant pressure alteration is observed, with peak pressures being greater than the traditional Joukowsky pressure rise. Elbow motion, driven by the axial stresses in the pipe and the fluid pressure, causes the alteration.; A numerical model is developed and verified with experimental data. The one-dimensional equations of continuity and momentum for the liquid and pipe wall are solved by the method of characteristics. At an elbow, coupling is introduced by continuity relationships. The translation of attached piping at an elbow is represented by an added stiffness term, and solved simultaneously with the characteristic equations. Comparison is shown between experimental data and predicted results. The equations are normalized and dimensionless parameters are identified that describe the liquid-pipe interaction. |
