Effect of flowing medium for a simply supported pipe subjected to impulse loading

Abstract

The primary aim of this study is to investigate the effects of a flowing medium on the transient response of a simply supported pipe subjected to dynamically applied loading. The importance of this study is manifested in numerous applications such as oil and gas transportation where dynamic loading can be the result of an accident. The classical Bernoulli-Euler beam theory is adopted to describe the dynamic behaviour of an elastic pipe and a new governing equation of a long pipe transporting gas or liquid is derived. This governing equation incorporates the effects of inertia, centrifugal and Coriolis forces due to the flowing medium. This equation can be normalised to demonstrate that only two non-dimensional parameters govern the static and dynamic response of the system incorporating a pipe and flowing medium. The transient response of this system is investigated based on a standard perturbation approach. Further, a numerical method utilising the finite difference method is developed and applied to investigate the dynamic response of a simply supported pipe. It is demonstrated that the previous dynamic models which largely ignore the internal flow effects and interactions between the flow and structure normally produce a large error and are inapplicable to the analysis of many practical situations. One interesting effect identified in the numerical study is that at certain flow ratio the system becomes dynamically unstable and any, even very small, external perturbation leads to a growing unstable dynamic behaviour. Such behaviour, which is called pipe whip, is well known to everyone who waters a garden using a flexible long hose.

Keywords:

• Flow-structure interactions
• flowing medium
• impulse loading
• pipe whip
• simply supported pipe
• transient response
• transporting gas or liquid

Additional information

Notes on contributors

R Mohammad

Roslina Mohammad joined the School of Mechanical Engineering at the University of Adelaide as a PhD student in July 2008, where she is currently doing research in impact mechanics. Roslina is currently a lecturer at University of Technology Malaysia (UTM) Kuala Lumpur, Malaysia.

A Kotousov

Dr Andrei Kotousov has 20 years’ experience in theoretical and experimental fracture mechanics, composites, bio-mechanics, and mathematical modelling. He is currently an Associate Professor with the School of Mechanical Engineering of the University of Adelaide.

J Codrington

John Codrington completed his PhD studies in 2008 at the University of Adelaide in the field of non-linear fatigue crack growth phenomena. He then commenced a postdoc position at the Bone and Joint Research Laboratory at the Institute of Medical and Veterinary Science (IMVS) in Adelaide, where he investigated the fracture resistance of human cortical bone. John is now working as a lecturer in the School of Mechanical Engineering at The University of Adelaide. General research interests include fracture mechanics, fatigue, structural health monitoring and bone mechanics. Current projects that John is involved with are the investigation of strength and fracture resistance in human bone, and fatigue crack repair via thermomechanical retardation.

A Blazewicz

Antoni Blazewicz is a lecturer in the School of Mechanical Engineering at the University of Adelaide. He completed his PhD studies in 2007 at the University of Adelaide in the field of acoustic radiation in flow over bluff bodies. His general research interests include experimental fluid mechanics, biological composite materials and sustainable air-conditioning. Current projects in which Antoni is involved are the investigation of strength and fracture resistance in human bone under different load conditions, and investigation of an adsorption refrigeration system which can be powered by solar power or waste water.