Bending vibration of a fluid-conveying tubular cantilever with a nozzle

Abstract

The present study is concerned with the vibration of a fluid-conveying tubular cantilever with a nozzle and its stability; the system is one of non-conservative system due to the follower force acting on the discharge end. In the concerning system, the follower force is the combination of Coriolis force and force due to momentum flux. It is found that the system damping initially grows and then decays as flow velocity increases, eventually the damping becoming negative and therefore the system becoming unstable. Presence of a nozzle mass tends to lower the critical flow velocity while the unstable mode remains the mode of no-nozzle case. It is also shown by simulation and experiment that the theoretical prediction without consideration of internal damping may lead to an erroneous result, since internal damping in a system may not only result in a change in unstable mode but lower the critical velocity.