Effect of the Body Number and Fluid Resistance on Stability of the Multi-Connected Body

Vibration behavior and unstable phenomena of multi-connected bodies supported by damper-spring elements moving in a narrow flow passage are reported. These vibration phenomena have been often observed in high-speed trains running in tunnels, cleaning robots going through pipings and so on. 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. The equations of coupled motion of the multi-connected bodies and fluid are derived. Using coupled equation, a stability analysis is performed. The effect of the flow velocity and number of bodies on the coupled mode is investigated. The influence of the boundary conditions of fluid pressure at connecting points is also investigated.