Frequency-domain analysis of fluid-structure interaction in aircraft hydraulic pipeline systems: numerical and experimental studies

The fluid-structure interaction (FSI) in aircraft hydraulic pipeline systems is of great concern because of the damage it causes. To accurately predict the vibration characteristic of long hydraulic pipelines with curved segments, we studied the frequency-domain modeling and solution method for FSI in these pipeline systems. Fourteen partial differential equations (PDEs) are utilized to model the pipeline FSI, considering both frequency-dependent friction and bending-flexibility modification. To address the numerical instability encountered by the traditional transfer matrix method (TMM) in solving relatively complex pipelines, an improved TMM is proposed for solving the PDEs in the frequency domain, based on the matrix-stacking strategy and matrix representation of boundary conditions. The proposed FSI model and improved solution method are validated by numerical cases and experiments. An experimental rig of a practical hydraulic system, consisting of an aircraft engine-driven pump, a Z-shaped aero-hydraulic pipeline, and a throttle valve, was constructed for testing. The magnitude ratio of acceleration to pressure is introduced to evaluate the theoretical and experimental results, which indicate that the proposed model and solution method are effective in practical applications. The methodology presented in this paper can be used as an efficient approach for the vibrational design of aircraft hydraulic pipeline systems.