Time-varying simulation of fluid dynamic pressure in oil pipelines under ground motion

Objective Upon being subjected to seismic activity, oil pipelines will undergo significant displacement alterations. It is crucial to understand the distribution characteristics of the fluid dynamic pressure along the pipeline length and its time-varying mechanisms affected by factors such as the liquid level of transmission medium and pipe diameter under ground motion.

Methods This study examined a fluid-pipe interaction system consisting of a simply-supported crossover pipeline with a 6 m span and transporting crude oil. Five finite element models were developed to simulate seismically induced dynamic pressure. By setting up respectively the initial conditions of the models, the seismic wave loading conditions and the boundary conditions of crude oil liquid level, the 30-second time-history responses of the fluid dynamic pressure were analyzed under varying pipe outer diameters and liquid levels. Results included dynamic pressure distribution nephograms over time for the same section, pressure distribution curves along the pipeline length, and time-history curves for key nodes.

Results The dynamic pressure in the pipeline reached a steady state 10 seconds after the fluid flow began. Upon inputting the ground motion time-history parameters, the dynamic pressure distribution along the pipeline length was uneven, with the most significant changes occurring in the mid-span area. The maximum difference between peak dynamic pressure values at different nodes on the same section was approximately 4.5 times. The liquid level of the crude oil significantly influenced the dynamic pressure induced by ground motion, with higher liquid levels corresponding to lower dynamic pressure under the same conditions. In pipes with an inner diameter of 1,118 mm, the dynamic pressure from crude oil flow was the lowest, but exhibited the greatest variability under ground motion.

Conclusion The research findings offer a theoretical basis for testing fluid dynamic pressure under ground motion and for the seismic design of oil pipelines.