Bidirectional Fluid–Structure Interaction Modeling and Experimental Validation for Pigging in Natural Gas Suspension-Span Pipeline

To minimize direct intervention on riverbeds and mountains, the construction of a natural gas suspension-span pipeline (SSP) has become the preferred environmentally friendly crossing solution. However, the high flexibility and low damping characteristics of the SSP make it prone to flow-induced vibrations due to the lack of rigid constraints during pigging, which can lead to structural failure. In the event of an oil and gas leak, it would cause immeasurable damage to the surrounding ecological environment. To address the lack of an assessment basis for the safety of SSP pigging, a dynamic response coupling model for SSP pigging was established based on d’Alembert’s principle, using pipeline displacement as the coupling parameter. Considering the relationship between the number of nodes in the finite-element model and the loading positions, a method for node force loading and compilation for gravitational and impact loads was proposed, enabling the solution of the coupling analysis model in finite elements. An experimental platform with a similarity ratio of 1/40 was built to conduct experimental tests and validate the model calculation results. The results showed that the average relative deviation of the maximum displacement SSP was −4.52%, confirming the accuracy of the model and the solution method. The calculation results indicated that under the same pigging conditions, the displacement at the midspan (1/2 span) was always the largest, followed by the 3/4 span and 1/4 span. Increases in pigging velocity and liquid accumulation will lead to an increase in the displacement of the crossing structure, providing a theoretical and data foundation for the safety of SSP pigging.