Free vibration of an extended pipe conveying fluid with distributed retaining clips

Retaining clips are essential components in aircraft, commonly applied to secure fluid-conveying pipes. This paper proposes a fluid-conveying extended pipe with two retaining clips, and its free vibration and stability are investigated. The Hamilton principle is applied to deduce the dynamic model of the system, and the complex frequencies and mode shapes are determined using the spectral element method. Dimensionless analysis indicates that variations in flow velocity, axial force and structural damping can lead to buckling or flutter in different modes. The selection of appropriate torsional damping is crucial to ensuring the stability of the pipe. Notably, the installation position of retaining clips may induce abrupt transitions between different instability modes. In addition, as the distance between the retaining clips on the extended pipe decreases, the influence of fluid–structure interaction on the mode shapes of segment B gradually diminishes, and the fixed nodes appear in the corresponding mode shapes. This study provides an in-depth analysis of the dynamic behavior of extended fluid-conveying pipes, which offers valuable insights for understanding the vibration characteristics of aircraft hydraulic pipes.