Experimental Study on a Buckling of an Up-Standing Pipe Conveying Fluid

Abstract

Long term efforts have been poured to the dynamics of a spring supported pipe conveying fluid. One of the reasons why this problem attracts the interest of many researchers is that this system shows the doubly degeneracy, pitchfork and Hopf bifurcations. At the point of double degeneracy, the buckling and the self-excited vibration in a certain mode occur simultaneously. It can be considered that such instability is widely existed in the non-self-adjoint systems. Up-standing pipe is typical example of such systems. In this study, we investigate the unstable phenomena of an up-standing pipe conveying fluid. First, we theoretically investigate the linear stability of an up-standing pipe conveying fluid. In case the gravitational force acting on the pipe becomes so large that it can overcome the flexural restoring forces, the first instability of this system is buckling in the first mode. When the flow velocity is over a certain value, the first mode gains the stability. As the flow velocity increases further, the self-excited vibration in a certain mode can be produced. Second, we conducted the experiments to confirm the steady state of the system. In particular, we conducted three dimensional quantitative measurements of the pipe motions. We observed some interesting motions.