Dynamic characteristics and responses of flow-conveying flexible pipe under consideration of axially-varying tension

Abstract

As oil and gas industry is developing towards deeper ocean area, the length and flexibility of ocean pipes become larger, which may induce larger-amplitude displacement of flexible pipe response due to lower structural stiffness against environmental and operational loads. Moreover, these pipes also convey internal flow. In other words, the dynamic characteristics and response of the flow-conveying pipe face great challenge, such as bucking and flutter.In this study, the dynamic characteristics and response of a flexible pipe, under internal flow and, particularly, axially-varying tension, are examined through our FEM numerical simulations. First, the governing equations and FEM models of a flexible pipe with axially-varying tension and internal flow are developed. Then the dynamic characteristics, including the coupled frequency and modal shape, are presented. At last, the dynamic response and corresponding stability behaviors are discussed and compared with the cases of pipe with uniform tension. Our FEM results show that the stability and response are quite different from pipe with uniform tension. And, the time-spatial evolution of pipe displacement exhibits a profound wave propagation effect, e.g. the wave length and peak value/position significantly change along structural length and the mechanism is discussed based on the WKB solutions.