Research on Natural Characteristics of Three-Dimensional Vibration of L-shaped Pipe
Fluid-conveying pipelines are crucial in various engineering fields for transporting media,and their vibration characteristics are a key focus for dynamics researchers.Due to the diversity of pipeline shapes,con-structing dynamic models for complex configurations is particularly important.This study employs the Absolute Nodal Coordinate Formulation(ANCF)to establish a three-dimensional dynamic model for pipelines and ana-lyzes an L-shaped pipeline with elastic supports at both ends as a case study.The system dynamic equations were derived using the generalized extended Lagrange equations.The modal results were validated using ANSYS software,and the effects of vertical and torsional spring stiffness,fluid velocity,structural parame-ters,and internal fluid filling rate on the natural frequencies were analyzed.The results indicate that increasing vertical and torsional stiffness enhances the natural frequencies,with vertical stiffness having a more significant impact.The inflection points of the low-order frequency curves appear earlier than those of the high-order fre-quencies.Increasing wall thickness,pipe diameter,and shortening pipe length significantly raise the natural fre-quencies and critical velocity.Changes in the filling rate do not significantly affect the natural frequencies at low flow velocities but significantly change the critical velocity.This study provides a reliable three-dimensional dynamic model for analyzing flow-induced vibrations in complex-structured pipelines.
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