Dynamics of Branched Pipeline Systems Conveying Internal Unsteady Flow

The pipeline system conveying high pressurized unsteady internal flow may experience severe transient vibrations due to the fluid-pipe interaction under the time-varying conditions imposed by the pump and valve operations. In the present work, a set of fully coupled dynamic equations of motion for the pipeline system are developed to include the effect of the circumferential strain due to the internal fluid pressure. A finite element formulation for the fully coupled dynamic equations of motion is introduced and applied to several sample pipeline systems. The connectivity conditions for both fluid and structural variables at the junction of a branched pipeline system are properly incorporated in the finite element formulation. To ensure the validity and accuracy of the present theory of pipedynamics, the same pipeline system considered in a reference work is revisited and the present numerical results are compared with those given in the reference work. A series pipeline system with high reservoir head is then analyzed to investigate the effect of the additional linear/nonlinear coupling terms in the present pipedynamic theory. Numerical tests show that the nonlinear coupling terms may become significant at high fluid pressure and velocity.