Abstract
This paper reports the vibrational behavior and unstable phenomena of multi-connected bodies supported by damper-spring elements moving in a narrow flow passage. These vibrational phenomena have been often observed in high-speed trains running in tunnels, cleaning robots going through pipings, medical machines in human blood vessels and core internal structures in nuclear reactor vessels. The fluid forces acting on the multi-connected rigid bodies are obtained analytically on the basis of the Navier-Stokes equations applied to a narrow flow passage. After the equations of coupled motion of the multi-connected bodies and fluid are derived, a stability analysis is performed, taking physical dimensions such as gaps etc. as parameters.
