抄録
When a hanging articulated pipe is vertically excited at random in water, the dynamic behavior of the pipe is analyzed as a dynamic problem of a system with random parametric excitation and nonlinear damping. Though this system may become unstable under certain input conditions, the response does not diverge, due to the fluid drag force in proportion to the squared velocity. In this study, the response under the instability condition was analyzed. A model experiment was also carried out to confirm the analytical model. As a result, a simple equation between the input and the response was derived, and was confirmed by the model experiment. It was seen that this simple equation is valid for a small input, and the root mean square of the response velocity is proportional to the power spectral density of the parametric excitation at twice the natural frequency of the excelling mode.
