Nonconservative pipes conveying fluid: evolution of mode shapes with increasing flow velocity

Abstract

When the velocity of fluid flow in a cantilevered pipe is successively increased, the vibration characteristics of the system may vary remarkably. This paper is concerned with exploring the evolution of the actual mode shapes of the pipe with increasing flow velocity. Results show that the mode shapes of the cantilevered system may dramatically change due to the increment of flow velocity. At higher flow velocity, these mode shapes, indeed, differ much from those of the classical cantilevered beam. When a critical mass ratio at which the so-called ‘mode exchange’ phenomenon occurs was chosen, the corresponding two modes of the cantilevered pipe would have the same shape. In addition, the nonlinear responses of the system have also been linked to the lowest three mode shapes by comparing the calculated mode shapes with the limit-cycle motions obtained experimentally.