STABILITY AND MODE EVOLUTION CHARACTERISTICS OF A CANTILEVERED FLUID-CONVEYING PIPE ATTACHED WITH THE LUMPED MASS

This work mainly investigates evolutions for the dynamic characteristics of a cantilevered pipe conveying fluid by regulating a lumped mass along the pipe's length, for the purpose of controlling the stability and vibration behaviors of the pipe. Firstly, on the base of the extended Hamilton principle, a nonlinear dynamic model for the cantilevered fluid-conveying pipe attached with the lumped mass is established. In the following, a linear analysis is performed to explore the evolution of critical flow velocity varying with the placed position of lumped mass, which is substantiated by experimental measurements showing that transition of the flutter mode occurs. In addition, it is significant that the attached lumped mass ratio has a great impact on the critical flow velocity based on the linear dynamic analysis, which is dependent on the placed positions and mass ratio. Subsequently, a nonlinear analysis is conducted to investigate the effect of lumped mass on vibration amplitude of the pipe. It is indicated that the vibration amplitude is first increased and then decreased with the lumped mass varying from the fixed end to the free end, which is well compared to those of experimental measurements. The vibration mode of the pipe conveying fluid is transferred from the second mode to the third mode with varying the placed position of lumped mass, which is also observed in the experiments. The present study is expected to be beneficial for designing an underwater driven system based on flutter of pipes conveying fluid. In this way, the pipe's vibration mode can be adjusted through adding and adapting the lumped mass.